Chapter 2
IS MATTER AROUND US PURE ?
️ Substance :-
It is a type of matter which cannot be separated into other types of matter by physical processes. A pure substance is made up of only one type of particles.
❇️ Mixture :-
A mixture is a substance made up of two or more elements or compounds (without being chemically combined). Example :- Air
️ Types of Mixtures :-
There are two types of mixtures .
- homogeneous mixture
- heterogeneous mixture
️ Mixed Mixture :-
Those mixtures in which substances are completely mixed with each other and are indistinguishable from each other are called homogeneous mixtures.
The whole mass has uniform composition.
Example :- The solution of sugar and (sugar) in water is homogeneous mixture.
️ Heterogeneous Mixture :-
Those mixtures in which substances remain separate and one substance is dispersed everywhere in another substance in the form of small particles, small droplets or bubbles, are called heterogeneous mixtures.
In a heterogeneous mixture, it does not have the same composition throughout its mass.
Example :-
- A mixture of sugar (sugar) and sand (sand) is a heterogeneous mixture because different parts of the mixture will have different mixture components of sugar and sand.
- Suspension of solids in liquids is also a heterogeneous mixture.
️ Solution :-
A solution is a homogeneous mixture of two or more substances.
Example :- Lemon water, soda water etc. are examples of solutions.
️ Types of Solution :-
A solution is divided into two parts solvent and solute .
️ Solvent :-
The component of the solution which is present in large quantity is called solvent.
️ Soluble :-
The component of the solution which is present in small quantity is called solute.
️ Properties of solution :-
- A solution is a homogeneous mixture.
- The particles of the solution are smaller than 1 nm in diameter. Therefore they cannot be seen with the eye.
- Due to their small size, the particles of the solution do not propagate the passing light. Therefore, the path of light is not visible in the solution.
- The particles of solute cannot be separated from the solution by the method of filtration. The particles of the solute do not settle down even if the solution is left still, that is, the solution is stable.
️ Concentration of solution :-
The amount of solute dissolved per liter of a solution's volume is called the concentration of the solution.
️ Saturated solution :-
If the solute does not dissolve in the solution at a given temperature, it is called a saturated solution.
️ Unsaturated solution :-
If the amount of solute in a solution is less than saturation then it is called unsaturated solution.
️ Supersaturated solution :-
If the concentration of the solute in the solution is more than the saturated level, then it is called supersaturated solution.
❇️ Suspension :-
A suspension is a heterogeneous mixture in which the particles of the solute do not dissolve, but remain suspended in the mass of the medium. These suspended particles can be seen with the eye; For example , flour water mixture, sand water etc.
️ Properties of suspension :-
- It is a heterogeneous mixture.
- These particles can be seen with the eyes.
- These suspended particles scatter the beam of light, making its path visible.
- When it is left still, these particles settle to the bottom i.e. the suspension is temporary. These particles can be separated from the mixture by filtration method.
️ Colloids :-
The solution in which the particle size is between 1nm to 1000nm is called a colloid.
Such as :- Starch solution, milk, blood etc.
️ Properties of colloids :-
- It is a heterogeneous mixture.
- The particles of colloids are so small that they cannot be seen separately with the eye.
- When these are left silent then these particles sit on the plane i.e. they are stable.
- These cannot be separated from the mixture by filtration method. But separation can be done by a special method, centrifugation technique.
- They are so big that they spread the ray of light and make its path visible.
️ Tyndall Effect :-
The spread of light rays by colloidal particles is called Tyndall effect.
️ Methods of separating the mixture :-
1. Evaporation :-
Basic Purpose :- Evaporation of one of the two substances of the mixture (e.g. the boiling point of one substance is lower than the other.
🔶 2. Decentralization :-
Basic purpose (theory): - Separation due to the density of particles or substances When a substance is rapidly rotated (denser particles) the heavier particles exert pressure on the bottom and the lighter particles move up.
3. Separation Funnel :-
Basic principle: - Two insoluble liquids (which both cannot dissolve together) can be easily separated by a separation funnel. By opening the stop cork of the separating funnel, water can be collected in the second beaker and the remaining oil can be collected in the second beaker.
4. Sublimation Method :-
Basic principle: - One substance sublimes between two substances (directly changing from solid to gas) while the other remains as it is.
5. Chromatography :-
Basic principle:- Colored compounds in a mixture can separate pigmented particles. With the help of an absorbent filter paper, when the particles of water (or any solution) move upwards with two different colors, then both are separated by chromatography paper. Because both the colors are absorbed at different speeds.
6. Distillation Method :-
Basic Principle: Between two components, the boiling point of one is lower than that of the other. This method is used to separate two or more soluble liquids.
7. Crystallization :-
Basic Principle :- To remove impurities from a mixture, first dissolve in a suitable solution and separate a component by crystallization.
️ Physical Change :-
The change in which there is an internal transformation of the states of matter, but there is no change in the composition and chemical nature of the substance, is called physical change.
Example:- Water dissolves in salt, bulb burns, wax melts etc.
️ Chemical Change :-
Changes in which one or more substances are changed into another substance are called chemical changes.
Example :- Rusting of iron, burning of carbon to form carbon dioxide.
️ Elements :-
The basic form of matter, which cannot be broken down into other simpler substances by chemical reaction, is called an element.
Such as: - sodium, copper, iron etc.
️ Classification of Elements :-
Elements are classified into metals, non-metals and metalloids .
Metal :-
Those elements which give up one or more electrons from their atoms in normal reactions are called metals.
Such as:- copper, iron, silver etc.
Non-metals :-
Those elements which acquire electrons from atoms of other elements in normal reactions are called non-metals.
Such as:- Oxygen, Chlorine, Iodine, Bromine etc.
🔶 Submetals :-
Some elements show properties between metals and non-metals called metalloids.
Such as :- Boron, silicon, germanium etc.
️ Compound :-
The substance which is formed by chemical combination of two or more elements in fixed proportion is called compound.
Such as :- Sugar, salt, water etc.
Difference between mixture and compound :-
🔶 Mixture :-
- Elements or compounds only come together to form a mixture.
- No new substance is formed.
- Do not create any new substance.
- Composition is variable.
- The components present in the mixture show their properties and religions.
- The components can be easily separated by physical methods.
Compound :-
- One substance reacts to form a new substance.
- The composition of a new substance is always permanent.
- They come together in a certain proportion according to their mass.
- The properties of the new substance are completely different.
- The components can be separated only by chemical or electrochemical process.
