Class 9th Science Chapter – 2 Is Matter Around Us Pure Notes In this Chapter We Will read about Is Matter Around Us Pure, Pure Matter, Mixture, Types of Mixtures, Homogeneous Mixture, Heterogeneous Mixture, Types of solutions, Solution, Concentration of a solution, Saturated Solution, Unsaturated solution, Supersaturated solution, Suspension, Metals and More much. you have provided easy notes which use in your study make progress in education.
NCERT Solutions Class 9th Science Chapter – 2 Is Matter Around Us Pure
Chapter – 2
Is Matter Around Us Pure
Notes
Pure
word means that there is no mixing in a substance. But according to scientific language all things are mixture of so many substances, not of single one. That’s why they are not pure. E.g. Milk, water, fat, etc.
Pure substances means that all elements have same chemical properties. A pure substance is made up of same kind of elements.
Pure Matter
When a substance is made up of only one type of particles, it is called a pure substance like – gold, copper, sodium chloride, sugar etc.
Substance
A substance is a kind of matter that cannot be separated into other kind of matter by any physical process. A pure substance is made up of same kind of elements.
Mixture
It is a substance in which two or more substances (element or compound) are simply mixed together in any proportion. Examples – The air is a mixture of oxygen, nitrogen, carbon dioxide and water vapour.
Types of Mixtures
There are two types of mixture
1. Homogeneous mixture 2. Heterogeneous mixture
Homogeneous Mixture
These types of mixtures have no visible boundaries of separation between the various constituents. Example – Sugar in water. It has a uniform composition throughout its mass.
Heterogeneous Mixture
These types of mixtures have visible boundaries of separation between the various constituents. Example – Mixture of sugar and sand. It does not have a uniform composition
Solution
A solution is a homogeneous mixture of two or more substances. Example – Nimbu pani, soda water.
Types of solutions
A solution is divided into two parts solvent and solute.
1. solvent 2. solute
Solvent
The component of the solution that dissolves the other component in it is called the solvent.
Solute
The component of the solution that is dissolved in the solvent is called the solute.
Properties of solutions
Solution is a homogeneous mixture .
The particles of a solution are less than 1 nm in diameter. That’s why they cannot be seen with the eye.
Due to their small size, the particles of the solution do not scatter the beam of light passing through them. That’s why the path of light is not visible in the solution.
The solute particles cannot be separated from the solution by the method of filtration. even when the solution is left to stand still
The particles of the solute do not settle down, that is, the solution is stable.
Concentration of a solution
The amount of solute dissolved per liter volume of a solution is called concentration of the solution.
Saturated Solution
If the solute does not dissolve in the solution at a given temperature, then it is called saturated solution.
Unsaturated solution
If the amount of solute in a solution is less than that of saturation then it is called unsaturated solution.
Supersaturated solution
If the concentration of solute in the solution is more than the saturation level, then it is called supersaturated solution.
Types of Mixtures
True
Colloidal
Suspension
1. Size of solute particles is smallest. < 10-9 m.
1. Size of solute particles bigger than true but smaller than suspension. In between 10-9 to 10-6 m.
1. Size of particles biggest. > 10-6 m.
2. Solute particles can’t be seen with naked eye.
2. Solute particles can’t be seen with Naked eye.
2. Can be seen with naked eye.
3. Homogenous mixture.
3. Seems homogenous but actually heterogenous mixture.
3. Heterogenous mixture.
4. Particles can’t be separated by filteration.
4. Particles can’t be separated by filteration.
4. Can be Separated filteration.
5. Transparent
5. Translucent
5. Ораquе
6. Stable solutions – i.e., solute particles do not settle on keeping.
6. Stable solutions.
6. Unstable solution-solute particles settle upon keeping.
7. Do not show tyndall effect.
7. Show tyndall effect.
7. May or may not show tyndall effect.
8. Solution diffuse rapidly through filter paper well as parchment paper.
8. Colloid particles pass through filter paper but not through parchment paper.
8. Suspension particles do not pass through filter paper as well as parchment paper.
9. e.g., Sugar in water.
9. e.g., Milk, blood.
9. e.g., Sand/mud in water.
Suspension
Suspension is a heterogeneous mixture in which the solute particles do not dissolve, but remain suspended in the bulk of the medium. These suspended particles can be seen with eyes like flour water mixture, sand water etc.
Suspension properties
It is a heterogeneous mixture.
These particles can be seen with eyes.
These suspended particles scatter the beam of light, making its path visible.
When it is left to cool then these particles settle to the bottom i.e. the suspension is temporary.
These particles can be separated from the mixture by the method of filtration.
Colloid
The solution in which the size of particles is between 1nm to 1000nm is called colloid. For example – starch solution, milk, blood etc.
Properties of colloids
It is a heterogeneous mixture.
The size of the colloidal particles is so small that they cannot be seen separately by the naked eye.
When these are left to cool then these particles settle on the bottom i.e. they are stable.
These cannot be separated from the mixture by filtration. But a special method can be separated by centrifugation technique.
They are so large that they spread the ray of light and make its path visible.
Tyndall Effect
The scattering of light by colloidal particles is called Tyndall effect.
Basic principal: Out of the two components of a mixture one can evaporate (i.e., has less boiling point] and other has higher boiling point. Example: Mixture of dye [higher boiling point] and water. Out of water and dye, water evaporates but dye is left behind in petri dish.
Centrifugation
The separation of colloidal particles due to it is called centrifugation.
Separating funnel
The process of separating two immiscible liquids is called a separating funnel.
Sublimation
Between two substances one substance is sublimated (converting directly from solid to gas) while the other remains as it is.
Chromatography
Colored compounds in a mixture can separate the pigmented particles. With the help of an absorbent filter paper, when the particles of water (or any solution) move upwards with two different colors, the two are separated by chromatography paper. Because both the colors are absorbed at different rates.
Distillation Method
Between two components, one has a lower boiling point than the other. This method is used to separate two or more miscible liquids.
Crystallization
The separation of a component from a mixture by first dissolving it in a suitable solution and crystallizing it to remove impurities.
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 matter, is called a physical change. For example – dissolution of water in salt, burning of bulb, melting of wax etc.
Chemical Change
Those changes in which one or more substances are converted into another substance are called chemical changes. For example – rusting of iron, burning of carbon to form carbon dioxide.
Element
That basic form of matter, which cannot be divided into other simpler substances by chemical reaction, is called an element. Like – sodium, copper, iron etc.
Classification of Elements
Elements are classified into metals, non-metals and metalloid
Metals
Those elements which lose one or more electrons from their atoms in normal reactions are called metals. For example – copper, iron, silver etc.
Nonmetals
Those elements, which accept electrons from the atoms of other elements in normal reactions are called nonmetals. For example – oxygen, chlorine, iodine, bromine etc.
Metalloid
Some elements showing properties between metals and non-metals are called metalloids. For example – Boron, Silicon, Germanium etc.
Compound
A substance which is formed by chemical combination of two or more elements in fixed proportion is called compound. For example – sugar, salt, water etc.
Difference between mixture and compound
Mixture
Compound
1. Elements or compounds are simply mixed so no new substance is formed.
1. Substances are reacted together with each other to make a new substance.
2. Elements do not combine in a fixed ratio.
2. Composition of the components is fixed i.e., they combine together in a fixed ratio according to their masses.
3. A mixture shows the properties of its components.
3. Compound doesn’t show the its components. properties of component elements.
4. Components can be easily separated by any mechanical method which is suitable.
4. Components can’t be separated from each other by simple mechanical methods.
5. e.g., sugar in water, oil in water
5. e.g., Iron and sulphur react to form iron sulphide.
Question 1. Define solvent.
The component of the solution that dissolves the other component in it is called the solvent.
Question 2. What is ‘tincture of iodine’?
A solution of iodine in alcohol is known as tincture of iodine. It has iodine (solid) as the solute and alcohol (liquid) as the solvent.
Question 3. Define solute.
The component of the solution that is dissolved in the solvent is called solute.
Question 4. Why water is called universal solvent?
Water can dissolve large number of substances in it.
Question 5. What is Tyndall effect?
The scattering of light by colloidal particles is known as Tyndall effect.
Question 6. What is emulsion?
When both the dispersed phase and dispersing medium is liquid, it is called emulsion. E.g., milk, face cream.
Question 7. What is aerosol?
When the solid or liquid is dispersed in a gas it is called aerosol. E.g., smoke, fog.
Question 8. How can you convert saturated solution into unsaturated or vice-versa?
Saturated solution on heating becomes unsaturated and unsaturated solution on cooling becomes saturated.
Question 9. What are alloys?
The homogeneous mixture of two or more metals or a metal and non-metal is called an alloy. E.g., steel is an alloy of iron and carbon.
Question 10. Give one example of gas in liquid solution.
Cold-drinks, carbon dioxide gas as solute is mixed with water as a solvent.
