Electroplating and it applications

Electroplating involves the process of coating the surface of one metal with another metal through electrochemical means. Electroplating is often done with the primary purpose  of  preventing rusting and improving the appearance of the plated object.

During electroplating, objects (mostly metals) are often coated with a layer of another metal by electrolysis. Example, the coating of knives and forks with silver to make it look shiny and stainless, and cheap jewelries are often coated with a layer of gold or silver. Electrolysis is simply the separation of a compound into it chemical parts by passing electric current through it molten a solution of it salt.

In the electrolytic cell, direct current is used to deposit a thin layer of a metal onto the surface of another metal, this is usually achieved by reducing the metal cations(i.e the positive ions) at the cathode(negative electrode) in order to form a solid metal precipitate on it. The metal to be electroplated is often used as the cathode. The anode is the pure metal to be deposited on the object. While the electrolyte is a solution of the soluble salt of the pure metal used as the anode.

How electroplating works

For us to grasp the full concept of electroplating, let's use a practical example of gold coating.

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Polar and non-polar molecules - meaning and differences

For example, an electron has a negative polarity e- that means that it has a negative electric charge. An ion of sodium posseses a positive polarity Na+ meaning it positively charged. Atoms and molecules has both positive and negative electric charge, their polarity only comes because one state of electric charge is greater than the other. For example, an atom can be negatively charged. This means that it has more negative charge carriers (electrons) than positive charge carriers (protons). This makes it has a negative polarity. Same goes for positively charged atoms. Some atoms and molecules can be neutral (having no electric charge). 

Polarity is just a state of having a positive and also a negative electric charge, especially in the case of magnetic or electrical poles. That phenomenon of seperation of electric charges into positive and negative is what is defined by the term polarity.

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Corrosion - Definition and types

Lots of metals are seen to change their colors, textures, and densities when exposed to air and moisture for an extended period of time. The picture above shows a car that was once new and shiny, but it has been broken down and roughened by reacting with components of the atmosphere. Another picture below shows a decaying and rough looking copper pipe that has experience partial degradation. In time, both metals will all be flakes.

 This two scenarios obviously shows that there is some form of invisible chemical reaction that leads to the irreversible damage of these metals when exposed to an open environment for a long time. Such chemical process is known as corrosion.

Definition of corrosion 

Corrosion is a process involving a metal being reconverted from it refined form to a  more chemically stable form such as oxides, hydroxides or sulfides  by natural means. 

During the process of corrosion, a metal is permanently and irreversibly degraded and broken down due to chemically and/ or electrochemically reacting with it environment.

Why does corrosion happens?

Metals are often gotten from their respective ores. Before any metal can be useful to create anything, it must first be extracted and refined from it ore. This ores can exist in form of oxides, sulfides, or salt. For example, iron(III)oxide or hematite is a common ore where iron is extracted, likewise in copper(I)sulfide for copper. These ores are most stable form in which  these metals can exist, and they always tend to remain in this stable forms.  So when extracted or refined for industrial purposes, they are less stable and they will look for any possible reaction in order to revert to stability.

Corrosion happens as the refined metals attempt to revert to their more stable raw or ore form.

Factors affecting corrosion

The reaction that causes corrosion can lead a metal to go back to it oxide or sulfide state when it react with an environments that contains traces of these compounds. The following are some factors influencing the rate or corrosion.

• Position of the metal in the electrochemical cell

The more reactive metals are easily corroded because when left exposed, it will have a higher tendency to to react with other elements like oxygen to form basic oxides. So the reactivity of the metal affects the corrosion

• Air or Oxygen.

It is the most important thing for corrosion i.e. oxidation of metal. More the exposure of metal to the air, more it will corrode. Most of the metals are corroded by the oxygen bust some of them by other gases like Copper by CO2, Silver by H2S, etc. For e.g. Copper develops a green colour coating on its surface due to the presence of air , moisture and carbon dioxide forms basic green malachite Cu(OH)2.CuCO3.

• Moisture

Moisture lead to formation of coordinate complex between metal oxide and water molecules like (Fe2O3. nH2O), etc. Moisture is present in the form of Water Vapour or capillary water in soils.

• Presence of other chemicals

Sometimes metals are corroded by the action of certain other chemicals like acids and bases. 

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covalent bond - definition, properties and examples

 A covalent bond can be define as a chemical bond which results when electrons are shared by two atoms. It only takes place between two non-metal atoms. 

When two atoms involved in a chemical bond formation do this through the sharing of the electrons in their outermost valence shell to achieve octet of electrons, covalent bonds are produced. Each covalent bond is formed from a pair of electrons, each of which is donated by each of the atoms involved in the bond formation. 

We will both explain the sharing of electrons in both non-metal elements and non-metal compounds.

Covalent bonds in non-metal elements

1. Hydrogen  

A hydrogen atom has only one shell, with one electron. The shell is capable of accommodating up to two electrons. When two hydrogen atoms get close enough, their shells overlap and then they can share electrons. Like this:

So each has gained a full shell of two electrons, like helium atoms. Each hydrogen atom has a positive nucleus. Both nuclei attract the shared electron - and this strong force of attraction holds the two atoms together. This force of attraction is called a covalent bond. A single covalent bond is formed when atoms share two electrons. 

The two bonded hydrogen atoms above form a molecule. A molecule is a group of atoms held together by covalent bonds. Since it is made up of molecules, hydrogen is a molecular element. Its formula is H2. The 2 tells you there are 2 hydrogen atoms in each

molecule.

2. Oxygen

An oxygen atom has six outer electrons, so needs a share in two more. So

two oxygen atoms share two electrons each, giving molecules with the

formula O2. Each atom now has a stable outer shell of eight electrons:

Since the oxygen atoms share two pairs of electrons, the bond between them is called a double bond. You can show it like this: O5O.

3. Chlorine

A chlorine atom needs a share in one more electron, to obtain a stable outer shell of eight electrons. So two chlorine atoms bond covalently like this:

Since only one pair of electrons is shared, the bond between the atoms is

called a single covalent bond, or just a single bond. You can show it in a

short way by a single line, like this: Cl2Cl.

Covalent bond in non-metal compounds

In a molecular compound, atoms of different elements share electrons.

The compounds are called covalent compounds. Here are three examples.

1. Hydrogen chloride(HCL)

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The chlorine atom shares one electron with the hydrogen atom. Both now have a stable arrangement of electrons in their outer shells: 2 for hydrogen (like the helium atom) and 8 for chlorine (like the other noble gas atoms). 

2. Water(H2O)

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The oxygen atom shares electrons with the two hydrogen atoms. All now have a stable arrangement of electrons in their outer shells: 2 for hydrogen and 8 for oxygen. 

3. Methane(CH4)

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The carbon atom shares electrons with four hydrogen atoms. All now have a stable arrangement of electrons in their outer shells: 2 for hydrogen and 8 for carbon.

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The hydrogen bond - meaning and examples

 

Hydrogen bond is an electrostatic force of attracted formed when a hydrogen atom is bonded covalently with a strongly electronegative atom such as chlorine or oxygen.

When hydrogen atom is bonded to an electronegative atom such as fluorine, oxygen or chlorine, its electron is attracted towards the electronegative atom, leaving the hydrogen atom with a partial positive charge; while the electronegative atom acquires a partial negative charge. This result in a slight polarity of the covalent bond between the hydrogen atom and the electronegative atom such that adjacent molecules tend to associate themselves in pairs, with the hydrogen atom acting as a bridge between those two atoms. The bridging bond between the hydrogen atom and the molecules, often represented by a dotted line, is called hydrogen bond. 

When the hydrogen bonds occur between two different molecules, they are called intermolecular hydrogen bond. When the hydrogen bond occur within the same molecule, they are called intramolecular hydrogen bonds.

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Definition and types of Oxides in chemistry

 Oxides are chemical compounds containing one or more oxygen atoms and another element combine together. Binary compounds are compounds containing two elements only. Oxides in general are binary compounds of metals or non-metals with oxygen, e.g. MgO, SO₂. 

The word binary is derived from the Greek prefix Bi meaning two. Binary compounds of oxygen are generally classified into four groups: 

1.  Acidic oxides
2. Basic oxides
3. amphoteric oxides
4. neutral oxides
5. neutral oxides

Acidic oxides

Acidic oxides are oxides formed between a non-metal and oxygen. They are oxides of non-metals which dissolve in water to form acids and react with alkalis to form salt and water only.

Let consider a situation where powdered carbon is heated over a Bunsen burner until red-hot, then plunged into a jar of oxygen. It glows bright red, and the gas carbon dioxide is formed according to the equation below:

C_(s) + O_2(g) → CO_2(g)

Another situation involves sulfur catching fire over a Bunsen burner, and burns with a blue flame. In pure oxygen it burns even brighter. The gas sulfur dioxide is formed according to the equation below:

S_(s) + O_2(g) → SO_2(g)

Carbon dioxide is slightly soluble in water. The solution will turn litmus red: it is acidic. The weak acid carbonic acid has formed. Sulfur dioxide  also dissolve in water to form acids. So they are all called acidic oxides. Acidic oxides in general combine with water to produce an acids, e.g.

CO_2(S) + H₂O_(l) → H₂CO_3(aq)

SO_2(S) + H₂O_(l) → H₂SO_3(aq)

In general, non-metals react with oxygen to form acidic oxides.

Basic  Oxides

A basic oxide is an oxide formed between a metal and oxygen.

Let likewise consider two situations. First will be that in which a magnesium ribbon is lit over a Bunsen flame, and plunged into a jar of oxygen. It burns with a brilliant white flame, leaving a white ash, magnesium oxide:

2Mg_(S) + O_2(g) → 2MgO_(s)

Second: Hot iron wool is plunged into a gas jar of oxygen. It glows bright orange, and throws out a shower of sparks. A black solid is left in the gas jar. It is iron(III) oxide:

4Fe_(S) + 3O_2(g) → 2Fe₂O₃

Ferric oxide is an example of iron(III)oxide occurring as rust or haematite

Basic oxides have two significant properties.

1.  Basic oxides react with acids to form a salt and water only.

CaO_(S) + 2HCl_(g) →CaCl₂ +  H₂O_(l)

MgO_(S) + 2HCl_(g) →MgCl₂ +  H₂O_(l)

2. If a basic oxide is soluble in water, it forms an alkaline solution.

CaO_(S) + H₂O_(l) → Ca(OH)_2(aq)

In general, metals react with oxygen to form basic oxides. Basic oxides belong to the larger group of compounds called bases.

Amphoteric oxides

An amphoteric oxide is an oxide of a metal which exhibit both basic and acidic characteristics. An amphoteric oxides shows two different types of reaction: basic and acidic.

An amphoteric oxide reacts with an acid to produce salt and water only, i.e. it behaves like a basic oxide and exhibit basic properties. E.g.

ZnO_(S) + H₂SO₄ → ZnSO₄ +  H₂O_(l)

An amphoteric oxide also react with an alkali solution to produce salt, i.e. it behaves like an acidic oxide and exhibit acidic properties.

ZnO_(S) + 2NaOH +  H₂O_(l) → Na₂Zn(OH)_4(aq)

An amphoteric oxide will react with both acids and alkalis

Neutral oxides

Some oxides of non-metals are neither acidic nor basic: they are neutral. Neutral oxides are oxides which shows neither basic nor acidic properties. The gases carbon(II)oxide (CO) and dinitrogen oxide,  (N₂O) are examples of neutral oxides. (Other nitrogen oxides are acidic.)

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Concept of electrovalent(ionic) bonding

 Electrovalent bond is a chemical bond formed as a result of the transfer of one or more electrons from one atom to another. Electrovalent bonds are only formed between metal atoms and non-metal atoms.

When an atom involved in a chemical bond formation completely transfer the electrons from it outermost valence shell to another atom that acquires the electron into it valence shell an electrovalent bond is formed. The atom that loses the electron will become positively charged while the atom that gains the electron will become negatively charged. Electrovalent bonds are otherwise known as ionic bonds because the resulting loss and gain of electrons will lead to the formation of cations and anions. The nature of the bonding in the compound called table salt (or sodium chloride) is a very common example of electrovalent bonding which will be used as a means of our explanation. But before we examine the nature of electrovalent(ionic bonding), let first remind ourselves of why atoms form bonds in the first place.

Why atoms form bonds? During chemical reactions, atoms bond with each other in order to gain a stable arrangement of outer-shell electrons, like the atoms of Group 0. In other words, they bond in order to gain 8 electrons in their outer shell (or 2, if they have only one shell).

How sodium and chlorine atoms bond together

A sodium atom has just 1 electron in its outer shell. To obtain a stable outer shell of 8 electrons, it must lose this electron to another atom, making it become a sodium cation according to the equation below.

Na  → Na⁺     + e^-

At the other hand, a chlorine atom has 7 electrons in its outer shell. It can reach 8 electrons and complete it outermost shell by accepting just 1 electron from another atom. Doing so will makes it becomes a chloride anion: The chloride ion has a charge of -1 so it is a negative ion. Its symbol is Cl^-

 As we can see, a sodium atom must lose one electron, and a chlorine atom must gain one, to obtain stable outer shells of 8 electrons. So when a sodium atom and a chlorine atom react together, the sodium atom loses its electron to the chlorine atom, and two ions are formed. Here, sodium electrons are shown as 'o' and chlorine electrons as 'ӿ'

The two ions have opposite charges, so they attract each other. The force of attraction between them is strong. It is called an ionic bond. The ionic bond is the bond that forms between ions of opposite charge.

Structure of ionic bond of sodium chloride

When sodium reacts with chlorine, billions of sodium and chloride ions form. But they do not stay in pairs. They form a regular pattern or lattice of alternating positive and negative ions, as shown below. The ions are held together by strong ionic bonds.

The lattice grows to form a giant 3-D structure. It is called ‘giant’ because it contains a very large number of ions. This giant structure is the compound sodium chloride, or common salt. Since it is made of ions, sodium chloride is called an ionic compound. It contains one Na⁺ ion for each Cl^- ion, so its formula is NaCl. The charges in the structure add up to zero: the charge on each sodium ion is 1⁺ the charge on each chloride ion is 1^- total charge = 0 So the compound has no overall charge.

Sodium is a metal. Chlorine is a non-metal. They react together to form an ionic compound. Other metals and non-metals follow the same pattern. A metal reacts with a non-metal to form an ionic compound. The metal atoms lose electrons. The non-metal atoms gain them. The ions form a lattice. The compound has no overall charge. Another example of electrovalent bonding in compound is magnesiumOxide MgO. 

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Polar and non-polar solvent - meaning and differences

 

 A solvent is a substance that can dissolve a solid, liquid, or gaseous solute, resulting in a solution.

There are generally two types of solvent depending on the type of compound that they dissolve. These include:

1. POLAR SOLVENT

2. NON-POLAR SOLVENTS

WHAT ARE POLAR SOLVENTS?

Polar solvents are those that possesses a large dipole moment due to the differences in the electro-negativities of their bonded atoms, and they are capable of dissolving polar compounds in a solutions. Water is a major example of a polar solvents.

WHAT ARE NON-POLAR SOLVENTS?

Non-polar solvents are solvents that have no dipole moment. Therefore, these solvents do not contain partial positive or negative charges. Due to this reason, these solvents are only able to dissolve non-polar 

compounds

 

When the electro-negativity of the bonded atoms is similar, at that time there is no dipole moment in a compound. This type of solvent are called non polar solvent. 

We have to types of non-polar solvents, which include;

• Aprotic solvents
• Non-Aprotic solvents

To further understand the concepts of these terms, let take a step backward to understanding what a chemical polarity and a chemical dipole is.

CHEMICAL POLARITY

In chemistry, polarity is a state of possession of a positive and a negative electric charges by an atom, a molecule, or a chemical group(such as a radical).

In molecules precisely, polarity is caused by the separation of charged particles, leading it to have a positive end and a negative end. 

more on chemical polarity →

CHEMICAL DIPOLE

In chemistry, a dipole refers to a molecule or a radical that has a concentration of positive electric charges at one end and a concentration of negative electric charges at the other end. A dipole moment occurs when a molecule’s positive and negative poles separate or move farther apart.

            Polarities in solvents occurs due to the nature of the bonding their molecules are made of. In a covalent bond, atoms may bond to form either a polar or a non-polar molecule. This polarity of molecules depend on the differences in the electro-negativity value of their bonded atoms. Electro-negativity is the abiity of an atom to attract electrons. Atoms in molecules are bonded by a covalent bond, which involves the sharing of electrons pairs. Sometimes in a covalent bond one atom can be more electro-negative than the other, causing a disparity in the electrons distribution in the bond, (one side of the bond will have a slight positive charge, while the other side will have a slight negative charge). When this happens, the type of molecule produced is called a polar molecule. But when atoms of the same level of electro-negativities bond together, there will be no disparity in electrons distribution in the bond, resulting in the formation of a non-polar molecule.

When a molecule is said to have a polar covalent bond, then the electrons of the atoms forming the bond are unequally distributed(one end will have slightly more electrons than the other end).The entire molecule will be a polar molecule, and they thus combine to form a polar compound.

On the other hand,  when the electrons of the atoms forming the bond are completely distributed in such a way that their net electrical charges cancel out, then the nature of the bond will be non-polar. the molecules will not have the charges present at the ends due to the reason that electrons are finely distributed.

The most common example of a polar solvent is water. A water molecule has two O-H bonds. The difference in electro-negativity between the oxygen atom and hydrogen atom is considerably high. Therefore, it is a polar covalent bond. The oxygen atom is more electro-negative. Hence, the oxygen atom gets a partial negative charge while two hydrogen atoms get a partial positive charge.

The reason why polar solvents are capable of dissolving polar compounds are because  both polar solvents and polar compounds have dipole moments and have oppositely charged moieties in the same chemical compound. The positively charged moiety of a solid compound can be attracted by the negatively charged moiety of a solvent molecule and vice versa, which can lead to the dissolution of the polar compound in the polar solvent.

In a solution, a polar molecule cannot be mixed with the non-polar molecule. For example, consider water and oil. In this solution, water is a polar molecule whereas oil behaves as a non-polar molecule. These two molecules do not form a solution as they cannot be mixed up.

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Emulsion - definition, properties, and examples

An emulsion is a mixture consisting of two or more liquids that normally do not mix well together or don't mix at all, but one is dispersed over another. The process of forming an emulsion by mixing  two or more different liquids is called emulsification. 

Emulsions are generally classified as colloids involving a mixture of two or more immiscible liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). The dispersed phase is a liquid in form of tiny droplets, crystals or particles with ultramicroscopic size, scattered and distributed throughout another phase of liquid, called the continuous phase.

The word 'emulsion' is gotten from the Latin word for "to milk", as milk is an emulsion of fat and water together with other components. The most common example of an emulsion is a mixture of water and oil. If you pour some oil into a cup of water, instead of the two liquids mixing together, the oil will just float on top of the water. Even if you try to stir them together, you'll notice that the oil and water will quickly separate again, forming two layers (or phases). Now if you beat up an egg and mix it with the oil and water, you'll also notice that the oil and water aren't separating into layers, but stays together. How is this possible? An emulsion is a mixture in which the substances combined are not soluble with each other or are immiscible. But the substances will not mix or stay mixed with each other without the help of what we called an 'emulsifier'. In the water and oil emulsion, the egg is the emulsifier.

TYPES OF EMULSIONS

Two liquids can form different types of emulsions. As an example, oil and water can form, first, an oil-in-water emulsion, wherein the oil is the dispersed phase, and water is the dispersion medium. Second, they can form a water-in-oil emulsion, wherein water is the dispersed phase and oil is the external phase. Multiple emulsions are also possible, including a "water-in-oil-in-water" emulsion and an "oil-in-water-in-oil" emulsion. Thus, we have two types of emulsions.

1. Oil in water(O/W) emulsion: In this type of emulsion, the oil will be the dispersed phase and water will be the dispersion medium. The best example for o/w emulsion is Mayonnaise. Mayonnaise is an oil-in-water (O/W) emulsion with a dispersed oil phase and a continuous water phase containing egg, vinegar, salt, sugar, mustard and water. The oil-water interface is stabilized by egg yolk, which acts as an emulsifier. Milk is also a perfect example. In milk, the fat globules (which act as the dispersed phase) are suspended in water (which acts as the dispersion medium).

2.Water in Oil(W/O) emulsion:  In this type, water will be the dispersed phase and oil will be the dispersion medium. Margarine (a spread used for flavoring, baking and working) is an example of water in oil emulsion.

DEFINITION OF EMULSIFIERS/EMULSIFYING AGENTS

Emulsifiers (or emulsifying agents or emulgents) are substances that stabilizes an emulsion or helps to keep an emulsion from separating. Below are images of certain mixtures showing before and after emulsification.

mayonnaise before and after adding an emulsifying agent

oil and vinegar emulsion before and after adding an emulsifying agent

PROPERTIES OF EMULSIONS

• Emulsions are fluid systems of tiny liquid droplets dispersed in another liquid.

• Emulsions are composed of two phases of heterogeneous liquid mixtures, known as the dispersed phase and the continuous phase. A boundary exist between the phases called the 'interface.

• The dispersed phase contains tiny droplets/particles which may be amorphous liquid crystalline, or any mixture thereof, having a diameter ranging from approximately 10nm to 100µm. 

• Emulsions, being colloids, do exhibit the tyndall effects by scattering light rays passing through it. That is why emulsions do tend to have a cloudy or whitish appearance especially when the light is scattered in equal proportion. This is as a result of the many phase interfaces scattering light passing through the emulsion. The more concentrated the emulsion is, the more higher-frequency (low-wavelength) light will be scattered more.

• The physical properties of emulsions do differ from that of it components. For example, while water and oil are transparent, emulsions are usually opaque and it can sometimes be design to have a lustrous and pearlized appearance. Also, while water and oil (for example) are thin free flowing liquids, emulsions can be made as think creams, that do not flow (like ice creams).

• Some emulsions due to presence of water lead to corrosion of the containers in which they are stored. An example is the containers used in paints. Packing of paints used to be in coated tin containers which were easily corroded. Plastic containers are in vogue now, largely avoiding the tin containers and the problem of corrosion associated with it.

• Emulsions can be converted into separate liquids by process of heating, centrifuging, freezing etc. This process of reconverting an emulsion into it components liquids is know as dimulsification.

EXAMPLES OF EMULSIONS

Some common examples of emulsions in everyday life includes:

•  Milk
•  hair creams
•  ice creams
•  paintings
•  mixture of oil in water and vice versa
•  Ointments
•  margarine
•  yogurts
•  asphalts etc.

USES/APPLICATIONS OF EMULSIONS

1. In medicines/pharmaceuticals : Lots of pharmaceutical products like some special body creams, soaps, toothpaste etc are in form of emulsions used for treatments of external disorders.

         Pharmaceutical emulsions are also used to deliver drugs that possess a low aqueous solubility. They can also be used to mask the taste of therapeutic agents, in which the drug is dissolved in the internal phase of an oil-in-water emulsion. Then the external phase then be formulated to contain the appropriate sweetening and flavoring agents.

2. In food productions: Several food products and soft drinks are considered as emulsions. Examples are: Milk, ice creams, yogurts, margarine, butter, Vinaigrette etc.

mayonnaise serves as sauce for salad and other food products

3. In Sprays: Sprays like insecticides, pesticides, and fungicides employ the use of emulsions as a medium for delivery. They are usually supplied in form of 'emulsifiable concentrate' (a solution of the pesticide in an organic solvents). This method helps in both farmland and livestock agriculture.

4. In cosmetics : In cosmetics, emulsions are the delivery vehicle for many hair and skin conditioning agents. Anionic and nonionic emulsions are used to deliver various oils and waxes that provide moisturization, smoothness, and softness to hair and skin. Emulsions formed with cationic emulsifiers are themselves effective conditioning agents since their positive charge is attracted to the negative sites on the hair, thus allowing them to resist rinse off.

5. In paintings: Many paints and inks are based on emulsions. Such products may be true liquid-in-liquid emulsions or they may be dispersion. Dispersion are similar to emulsions except that the dispersed phase is usually divided finely into solid particles. The same surfactant technology used to formulate emulsions is used to create dispersion of pigments that are used in paints and inks. These dispersion are designed to dry quickly and form waterproof films, while not affecting the color. In this regard emulsions provide benefits over solvent containing systems because of reduced odor and flammability.

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Suspension - meaning and examples

 

A suspension is a heterogeneous mixture, mostly involving a fluid and solid particles in which the particles are separated and scattered around the fluid without dissolving in it.

A suspension contains mixture of two or more substances which are not fully miscible with each other. The particles in a suspension, instead of dissolving in the liquid, spreads throughout the liquid and can be seen by the naked eye. 

A typical example of a suspension is a chalk dust in water. When chalk powders are added to water, the particles will not be dissolved but rather they will be spread throughout the water and if the mixture is left untouched, the dust will be settled at the base of the container and it can be filtered out.

Properties of a suspension

• Suspensions are heterogeneous in nature.

• The particles of a suspension do not dissolve but are rather suspended.

• Particles can be seen by the naked eye or by use of a microscope cause they are larger than 1 nanometer.

• Particles of a suspension exhibits the tyndall effect, thus they can scatter rays of light passing through it. 

• When left untouched for some time, particles get settled in the bottom of the container due to gravity and can be separated by ordinary filtration.

Examples of suspension:

       1. Muddy water: where salt, clay, or silt particles are suspended in water.

A suspension of sand in water

       2. Sand in water.

       3. Flour in water

       4. Dust particles in air.

       5. soot in air.

Other facts about suspensions 

A suspension of a liquid or solid particles in a gas is known as an aerosol. Particles suspended in the atmosphere are called particulates. Particulates of the atmosphere consist of fine dusts, soot, evaporated sea salts, blogenic and volcanic sulphates.

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Solution, Solute, and Solvent - meaning and differences

 Solution: A homogeneous mixture, which may be liquid, gas or solid, formed by dissolving one or more substances. 

A solution consists of a solvent and a solute.

Characteristics of a solution

1. It must be homogeneous

2. It is composed of just a single phase. Hence, it impossible to distinguish one components from another. For example, In a perfect sugar solution, you cannot distinguish the sugar in the water.

3. The solutes in a solutions cannot be seen by the naked eye.

4. Beam of light passing through it doesn't scatter, because it components are very tiny(about 1nm in diameter)

5. Component making up a solution cannot be separated by ordinary filtration.

Examples of solutions are:

• Mixture of salt or sugar in water
• Metallic alloys e.g steel, bronze are examples of solid solutions.
• Air
• Tea/coffee
• Bleach etc
• Juice

A homogeneous mixture is a mixture in which the component present have the same composition throughout and are uniform in their making. The component that make up a homogeneous mixture are distributed uniformly in such a way that they are indistinguishable(cannot be seen separately).

Examples of  homogeneous mixtures are: Pure water, steel alloy, air, blood plasma etc. 

A solution of salt in water

Solvent: A substance that is capable of dissolving other substances be it solid, liquid, or gas in other to form a solution. In a solution, the solvent always takes a larger portion. Solvents are mostly in liquid form. The two types of solvents are Polar and non-Polar solvents.

Characteristics of a solvent

1. It always takes a larger portion in a solution.

2. Solvents are mostly liquids, but they can sometimes come in forms of solid, gas or supercritical fluids.

3. They have a lower boiling point and can evaporate easily.

4. Solvents are sometimes advantages, as it helps to speed up a reaction, and also regulate the temperature of a solute.

Examples of solvents

• Water (universal solvent)
• Alcohols like methanol, ethanol etc.
•  Petroleum products and hydrocarbons like benzene, glycerol, acetone. toluene
• Chloroforms
• Milk, Oil, citric acids etc.

Can a solvent be in a Solid form?

When most people think of the term solvent, a liquid medium always comes to mind; however, there are both cases in which a solid or a gas can also acts as solvents.

While it is true in some cases that when dissolving, the solvent has to be in it liquid state, this is because the solvent has to get "between" the molecules of the solute to do its job, and that can only work when the solvent is liquid.  This explanation thus appears not to be always the case. Lets  see some examples:

 — Air is a homogeneous mixture of different gases including oxygen, nitrogen, and carbon(iv)oxide. This makes air a solution. The components of air making it a solution consists of different gases both acting as a solute and as a solvents. 

 — Steel and bronze are also an example of a homogeneous mixtures consisting of various solid metals. Steel consist of a mixture of iron and carbon, while bronze is composed of copper and tin. Here we can see that two solids also acts as a solute and a solvents, but in this case, both the solid-solute and the solid-solvents has to be melted before the can be dissolved.

Solute: Any substance that is dissolved in a solvent to create a solution is called a solute.This means that in a solution, the solute is the substance that is being dissolved by a solvent. For a solute to be dissolved by a solvents, the attractive force between their them must be stronger enough to overcome the molecular forces holding their  molecules. This will make them uniformly mix together.

The solutes only takes the smaller portion in a solution, while the solvents will take a larger portion. 

A solutes occurs mostly as solids, but they can also be in liquids and gaseous states.

Examples of solutes

• Sugar in a coffee
• Salts in seawater
• Oxygen in air
• Zinc, tin, and carbon in brass, bronze, and steel respectively.
• CO₂ in carbonated beverages like coca cola.

Characteristics of a solute

1. They possess the smallest portion in a solution

2. They can be in solid, liquid or gaseous state

3. They have a higher boiling points than solvents.

4. They possesses a solubility limits and they can be saturated.

EXTRA TERMS.

Solubility

It is the ability of a substance to dissolve in another substance, especially water. be it solid, liquid or gas. Different kinds of solutes and solvents has their different degree of how they dissolves or are being dissolved in a solution. And this depends on a number of factors, including temperature, pressure and mass.

Solubility Limit

This is the limit to how much a solute can be dissolved by a solvents in a solution. Using a salt and water example, if you keep adding excess salt to water, you will finally reach a point where the added salt remains as granuals and does not dissolve. At that point, the “solubility limit” has been reached. The solution is “saturated.” Once the solvent has dissolved all of a material that it can, it is no longer a solvent for that material. The solubility limit, though, typically increases as temperature increases. Increasing the temperature of a salt/water solution will allow more salt to be dissolved by raising the saturation limit. However, even a saturated solution may still be a solvent for another material.

SUMMARY

A solution is a homogeneous mixture of two or more substances.

A solution consist of a solute and a solvents

The substance which is being dissolved is called a solute and the substance in which the solute is dissolved is called a solvent. A mixture of solute and solvent is called a solution.

A solvents takes the greater portion in a solution, while the solutes takes the lesser portion.

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What is a Tyndall effect

  Tyndall effect is a phenomenon which involves the scattering of light rays by particles in a colloid or a very fine suspension when the beam of light passes through them.

When beams of lights are directed at a colloid or a very fine suspension, the individual particles of the colloid or suspension will not permit the light rays to freely pass through. Instead, the rays and the particles will undergo collision, resulting in the rays  being scattered and reflected by the particles. Making the path of the light visible.

In a solution, light travels in a straight line but when it passes through a colloid or a fine suspension, it will deviate as a result of getting reflected and dispersed by the colloidal particles, making the rays to appear visible. This phenomenon is called tyndall effects. It was named after an Irish physicist John Tyndall following this discovery.

The intensity of the scattered light depends on the frequency of the light and the size of the particles. It even stated that:  "the intensity of the scatterd light is inversely proportional to the fourth power of it wavelength". Thus, it is observed that blue lights (with a shorter wavelength) is scarttered strongly than red lights (with a longer wavelength).

You might be wondering;  'why is this reaction unique anyway'? Tyndall effects is quite responsible for so many color effects in most substances both organic and inorganic. A more common example of tyndall effect is evidence by the blue color of the eye. This is caused by light getting scattered by the translucent layer of the iris.

Other examples of tyndall effects includes:

• Scattering of light by particles of milk: Milk is an example of an emulsion (a type of colloid), containing rounded particles of fats and protein. When a flashlight is directed at a glass of milk, the light rays will scatter and the path will be visible in the glass.

• The blue colors presents in smokes from a motorcycle or a car is an example of tyndall effects, where light is scattered by smoke particles.

• Scattering of lights by water droplets in fogs: When a flashlight or a headlight is directed at foggy environments, the path of the light rays from the headlight will become visible as shown in the image below.

• When sunlight finds it way in a room where lots of dust particles are suspended, the dust particles will scatter the light from the sun, forming a visible path.

• In the laboratory, tyndall effects is used to distinguish between a true solution and a colloid solution. This is because the components forming a true solution are very tiny and unable to reflect any light rays that passes through them. While in a colloid, the particles are large enough to reflects light rays, exhibiting tyndall effect.

Another phenomenon which involves the scattering of light is the rayleigh effect.

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Colloid - definition, properties and examples

  A colloid is a type of a mixture containing two phases, in which one phase of the mixture is dispersed throughout  the other in form of a very small microscopic droplets or particles. In simpler terms, a colloid is a system in which one substance is dispersed as a very fine particle in another. A colloid appears to posses homogeneous features when viewed from the normal human eye, but when viewed using a microscope, it clearly composed of tiny particles of macromolecular structures, scattered throughout another medium which could be a liquid or a gas.

A typical example of a colloid is a fog. Here we can consider two phases of a mixture where liquid crystals are scattered around a gas, which in this case is air. 

Dispersed phase and dispersion medium

In a colloid, the phase which consist of substances which are scattered or present in form of colloidal particles is called the dispersed phase while the medium in which the colloidal particles are dispersed on is called the dispersion medium. 

The dispersed phase of a colloid is composed of very small minute particles, and it dispersed or suspended throughout another substance. These particles sometimes cannot be distinguished from the mixture with the naked eye, but only with the use of a strong microscope. They can range from 1 to 1000 nanometer in diameter and are larger than molecules, but tiny enough to remain evenly distributed throughout the mixture. Unlike a suspension, colloidal particles do not settle to the bottom of the container when left undisturbed overtime. 

Properties of a colloid

1. A colloid is a mixture composed of very tiny particles dispersed in a medium. 

2.  A colloid is made up of two phases namely; The dispersed phase and the dispersion phase (or medium).

3. BROWNIAN MOTION: The particles presents in a colloid neither settle, rest nor affected by gravity. They are constantly at a random zigzag type of movements. This type of uniformless or directionless movements is known as brownian motion. This therefore means that, unlike a regular suspension, no matter how long a colloid is left undisturbed, it dispersed particles do not separate out or settle at the bottom due to gravity.

4. TYNDALL EFFECTS: Colloids do exhibit the tyndall effect due to reasons that it particles although very tiny are large enough to scatter a beam of light shinning through it, making the path of the light appear visible.

5. Colloids are unable to pass through a porous membrane without filtering at least some of it particles, especialy if the pores have a size smaller than their dimension.

6. ELECTROSTATIC INTERACTION: particles in a colloid often posses electric charges, making them to attract or repel each other.

Types of colloids

Colloids are classified based on the physical states of it dispersion medium and it dispersed phase. Below are the types of colloids :

• SOLID SOLS
• SOLS
• SOLID AEROSOLS
• LIQUID AEROSOLS
• GELS
• FOAMS
• EMULSIONS

To understand it a little more simpler, let arrange them into three distinct groups, namely:

1. Solid Dispersion Medium : When the dispersion medium is solid, the dispersed phase can also be solid, liquid or gas. Based on the state of dispersed phase, colloids are either called Solid Sols or Gels.

• Solid Sols - solids dispersed on a solid. 

                                ► Gemstones, Pearls, some colored Glasses

• Gels - liquids dispersed on a solid.

                                 ►Butter, cheese, Jellies, Jam, Shoe polish

• Solid Sols - Gases dispersed on a solid.

                                 ►Pumice Stone, Foam Rubber

2. Liquid Dispersion Medium :  When dispersion medium is liquid, the dispersed phase can be solid, liquid or gas. Based on the state of dispersed phase, colloids are either called Sols,Emulsions or Foam.

• Sols - solids dipersed on a liquid.

                                  ► Paints, Gum, Muddy water 

• Emulsion - liquids dispersed on a liquid.

                                  ► Milk, Hair cream, Cod-liver oi

• Foam - gases dispersed on a liquid.

                                   ► Froth, soap lather, Whipped cream

3. Gas Dispersion Medium : When dispersion medium is gas, the dispersed phase can be solid or liquid but not the gas**. Colloids of gas with dispersed phase as solids or liquids are called Aerosols.

• Solid Aerosols

                                   ► Smoke, Dust, Clouds (Ice particle clouds)

• Liquid Aerosols

                                    ► Insecticide spray, Fog, clouds (water                                                                    particles/droplet clouds)  

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Ethalphy and Entrophy explained

 Entropy and enthalpy are both ways of measuring heat and its motion in various circumstances. In the case where hot systems are cooling or giving up their energy, or heating and absorbing energy, systems such as boilers, car engines, air conditioners, or all kinds of machinery these two thermodynamic “forces” come into play. Also at work is the idea of temperature which relates them.

Enthalpy is defined as H= U +PV, where U is the internal energy of the system and P is constant pressure, and V is volume. We are most interested in the change in enthalpy so usually we use ΔH = ΔU +PΔV. This means that a change in enthalpy results in a change in total energy and volume of a gas or liquid, and vice versa. A change of this sort involves also a change in temperature, and when we measure these together we encounter the concept of entropy.

Entropy is defined as ΔS= ΔH/T where T is the temperature in °K or °C. This is for a reversible transfer of heat between the system and its surroundings. Entropy measures the amount of disorder a system undergoes while transferring heat.

Rather than analyze complex systems I will illustrate with a simple instrument: A mercury thermometer. This device when inserted into a hot water bath captures some of the kinetic energy of the water molecules in the system and transfers it to the mercury in the thermometer. The mercury expands and shows the temperature on the markings on the glass. In thermometer A there is a small amount of air whose volume contracts when the mercury expands, but it has little effect on the reading itself as the mercury is not greatly affected by the air pressure here. So the differential enthalpy increases as the heat is absorbed and the volume expands, but once you take the thermometer out of the bath it cools and the enthalpy also goes down. Some of the heat has also increased the entropy inside the thermometer, as the molecules of air and mercury have increased in random activity due to heating, but once the thermometer cools down the entropy is returned to the air and mercury, so there is no net gain in entropy.

In thermometer B , however which has been broken at the top, the hot air escapes and the entropy of the system increases, because, in a large room the air molecules have escaped and increased their disorder, in a way that is not reversible easily, so the entropy of the system has changed and increased.

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All separation techniques explained

 One major activity in chemistry is the analysis of materials in our environment. Many materials found in our environment are mixtures, and we often want to separate the constituents of a mixture. In chemistry, the separation of constituents of  mixtures involves the application of simple principles and use of special pieces of apparatus. This process of separating mixtures into it component part is known as 'separation technique'. Pure substances can also be obtaned from impurities by using various methods of separation techniques.

There are different types of mixtures:

• Mixture of a solid and liquid e.g. precipitates.

• Mixture of a liquid and gas e.g. carbonated drinks.

• Mixture of a solid and solid e.g steel

• Mixture of a gas and gas e.g. air

The methods and principles which are applied in the separation of mixtures in chemistry are based on the special properties of the constituents of the mixtures. Such properties like different boiling points, different densities, different solubilities are frequently used. 

Methods of separating mixtures

The different methods and techniques used in separating mixtures includes:

<table like pdf>

These methods are used to separate different kinds of mixtures which are explained in full details below.

1. Separating solids from liquids

The method used in separating a less dense liquid and an insoluble and denser solid depends on whether the solid is dissolved, and how its solubility changes with temperature. Three methods are thus possible.

a.  By filtration

Filtering involves the process of pouring the mixture into a porous material, e.g filter paper. During filtration, the liquid portion passes through the filter paper while the solid material remains on the paper. The liquid which passes through the  filter paper is called the filtrate while the portion which remains on the filter paper is called the residue.

For example, chalk is insoluble in water. So it is easy to separate by filtering.The chalk is trapped in the filter paper, while the water passes through.The trapped chalk particles is the residue. The water is the filtrate.

<image from pdf>

2 By crystallisation

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What is the difference between Base and Alkali

In chemistry, it sometimes difficult for some student to distinguish or grasp the full understanding between a Base and an Alkali. Sometimes, you'll probably hear something like "all alkalies are bases but not all bases are alkalies". Without much more in depth reasoning, you won't get it right. This post will save you that stress. Let start by defining a base.

What is really a base

Substances that have a soapy feel, taste bitter, turns red litmus paper blue, and generally possesses the ability to neutralize an acid are classified as bases. 

          A Base is simply a substance that is used to neutralize an acid. But how?  To neutralize simply means to weaken the strength of something by adding an opposing effect. So in this case, neutralization reactions are when an acid react with a base to form water and a salt. So a base react with an acid in order to make it neutral. One reason an acid is neutralized is in the sector of agriculture, where a soil happens to be more acidic and it pH drops. By adding a substance(like a base) which will neutralize the acidity of the soil, it will be possible to raise the pH to more neutral levels for plant to grow effectively.

        Bases comes in form of metal hydroxides (metal+ OH^-) and metal oxides ( metal+ O^2-). Examples of bases include:  Sodium Oxide(Na₂O), Copper Oxide (CuO), potassium Oxide (KOH),  Sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)₂ ) Calcium Oxide (CaO), potassium Oxide (K₂O) etc.

Then what is an alkali

You may have notice in the above examples that some bases ends with "OH", while some are accompanied by just a single "O". That is the point. Those that ends with OH are example of bases called alkali.

        An Alkali is just a kind of base that dissolves in water. Let use our above examples again.

As you can see, when water is added to sodium oxide(Na₂O), it gives sodium hydroxide (NaOH) which is therefore a soluble base or (you guess it right) an Alkali. Same with subsequent ones. Not all bases are soluble in water, so when a base dissolves in water, it is termed as alkali, and now based on our understanding, we can say that since not all bases are soluble in water,  therefore not all bases are alkali but since alkali are just an example of bases that dissolves in water, then all alkali are bases.

Hope you understand. If you have any challenge based on this topic, or any other science related topic you will like me to address, just include it on the comment box below.Thanks.

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Why is it said that electrons are negatively charged

 The separation of electric charges into positive and negative still sounds much of a brain box to some curious new physicist, especially in the field of electrical and electronics engineering. But the interesting fact about this is that it was all because of Benjamin franklin's arbitrary decision.

Are you actually a curious type? Do you want to know they full fact behind the ideas that :

1. Electrons possesses a negative charge, while protons are positively charged.
2. Like charges repel while unlike charges attract

This post will explain all of the in depth concept of electric charges using the theory of static electricity. 

Why do knowing these facts matter:   Real scientists and inventors who make a difference don't only limit themselves with implicit explanations, but they move further to know more on the underlying concept of scientific theories. Of cause there is no big deal about just seeing things as everyone does, but to be an inventor, you'll have to be curious enough to fully grasp the root cause of how things actually works, not just how to make things.

What are charges anyway 

To understand the concept of electric charges, let first revisit the past a bit.

          It was discovered centuries ago that certain types of materials would mysteriously attract one another after being rubbed together. For example: after rubbing a piece of silk against a piece of glass rod, the silk and glass would tend to stick together. Also, when a paraffin wax is rubbed with wool cloth; they are seen to attract each other. Indeed, there was an attractive force that could be demonstrated even when the two materials were apart.

This phenomenon became even more interesting when it was discovered that identical materials, after having been rubbed with their respective cloths, always repelled each other. For example: lets consider two glass rods rubbed with silk and brought together. They are seen to repel each other:

Even the materials used to do the rubbing will also tend to repel each other. For example: Two wool cloths will be seen to repel each other after they were used to rub different paraffin wax. Same goes for two silk cloths used to rub different glass rods.

What could have caused this invisible force of attraction and repulsion?  Whatever change that took place to make these materials attract or repel one another was invisible.

         Some experimenters speculated that invisible ”fluids” were being transferred from one of the material to another during the process of rubbing, and that these ”fluids” were able to effect a physical force over a distance. Charles Dufay was one of the early experimenters who demonstrated that definitely two different  types of changes  took place by rubbing certain pairs of objects together.  This idea that there was more than one type of change manifested in these materials was due to the fact that  two types of forces were produced: attraction and repulsion. The hypothetical fluid transfer became known as a CHARGE.

         

What is the concept of positive and negative charges

 One pioneering researcher, Benjamin Franklin, came to the conclusion that there was only one fluid exchanged between rubbed objects, and that the two different ”charges” were nothing more than either an excess or a deficiency of that one fluid. After experimenting with wax and wool, Franklin suggested that the coarse wool removed some of this invisible fluid from the smooth wax, causing an excess of fluid on the wool and a deficiency of fluid on the wax. The resulting disparity in fluid content between the wool and wax would then cause an attractive force, as the fluid tried to regain its former balance between the two materials. 

           His postulations reveal that during the rubbing process, the two materials concern must fall into either of the two opposing categories. In other words, one must be in excess while the other must be in deficiency. There was never a time where two materials rubbed against each other both became either in excess or in deficiency. 

          Following Franklin’s speculation of the wool rubbing something off of the wax, the type of charge that was associated with rubbed wax became known as ”NEGATIVE” (because it was supposed to have a deficiency of fluid) while the type of charge associated with the rubbing wool became known as ”POSITIVE” (because it was supposed to have an excess of fluid). Little did he know that his innocent conjecture would cause much confusion for students of electricity in the future!

 

 NOTE: The idea of using negative and positive as the word was simply an arbitrary decision by franklin. Since the word "negative" always refers to lack of something and positive designated to a possession of...  

Why is the word "negative" designated to Electrons and "positive" to protons

        It was discovered much later that this ”fluid” was actually composed of extremely small bits of matter called  ”ELECTRONS ”, so named in honor of the ancient Greek word for amber: another material exhibiting charged properties when rubbed with cloth. Experimentation has since revealed that all objects are composed of extremely small ”building-blocks” known as ATOMS, and that these atoms are in turn composed of smaller components known as particles. The three fundamental particles comprising most atoms are called protons, neutrons and electrons. 

However, electrons have significantly more freedom to move around in an atom than either protons or neutrons. In fact, they can be knocked out of their respective positions (even leaving the atom entirely!). If this happens,  an important imbalance will  occur. Electrons and protons are unique in the fact that they are attracted to one another over a distance. It is this attraction over distance which causes the attraction between rubbed objects, where electrons are moved away from their original atoms to reside around atoms of another object.

            Electrons tend to repel other electrons over a distance, as do protons with other protons. The only reason protons bind together in the nucleus of an atom is because of a much stronger force called the strong nuclear force which has effect only under very short distances. Because of this attraction/repulsion behavior between individual particles, electrons and protons are said to have opposite electric charges. That is, each electron has a negative charge, and each proton a positive charge.

The process of electrons arriving or leaving is exactly what happens when certain combinations of materials are rubbed together: electrons from the atoms of one material are forced by the rubbing to leave their respective atoms and transfer over to the atoms of the other material. In other words, electrons comprise the ”fluid” hypothesized by Benjamin Franklin. The result of an imbalance of this ”fluid” (electrons) between objects is called static electricity. It is called ”static” because the displaced electrons tend to remain stationary after being moved from one insulating material to another. In the case of wax and wool, it was determined through further experimentation that electrons in the wool actually transferred to the atoms in the wax, which is exactly opposite of Franklin’s conjecture! In honor of Franklin’s designation of the wax’s charge being ”negative” and the wool’s charge being ”positive,” electrons are said to have a ”negative” charging influence. Thus, an object whose atoms have received a surplus of electrons is said to be negatively charged, while an object whose atoms are lacking electrons is said to be positively charged, as confusing as these designations may seem. By the time the true nature of electric ”fluid” was discovered, Franklin’s nomenclature of electric charge was too well established to be easily changed, and so it remains to this day.

Why do like charges repel and unlike charges attract

If we take the examples of wax and wool which have been rubbed together, we find that the surplus of electrons in the wax (negative charge) and the deficit of electrons in the wool (positive charge) creates an imbalance of charge between them. This imbalance manifests itself as an attractive force between the two objects:

The imbalance of electrons between the atoms in the wax and the atoms in the wool creates a force between the two materials. With no path for electrons to flow from the wax to the wool, all this force can do is attract the two objects together

Dedicated to the book "Lessons In Electric Circuits, Volume I – DC"

 By Tony R. Kuphaldt

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