Ans. We consider anything as pure, when the matter is made up of only one type of particle. It is also known as a substance.

Ans. Any matter, which has different types of particles as its composition, is called a mixture.

Pure	Mixture
It has only one type of particle.	It has different types of particles.
Its constituents cannot be separated by physical process.	Its constituents can be separated by physical process.

Ans. There are two types of mixtures:

1. Homogeneous Mixture
2. Heterogeneous Mixture

Ans. There are two types of pure matters:

1. Elements
2. Compounds

Ans. A mixture, whose constituents are in the same ratio throughout the matter, is called a homogeneous mixture.

Examples: Air, sugar solution, petroleum, alloy etc.

If we taste a sugar syrup then its sweetness is the same throughout the solution. It demonstrates that components of the sugar syrup (sugar and water) are the same throughout the solution. Similarly, air contains nitrogen (78%), oxygen (21%) and other gases (1%) uniformly.

Ans. A mixture, whose constituents are not in the same ratio throughout the matter, is called a heterogeneous mixture.

Examples: Milk, mixture of sugar and salt, mixture of two different pulses etc.

If we take one spatula of a mixture of sugar and salt and count the crystals repeatedly, the ratio of sugar crystals to salt crystals is not the same every time.

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

Ans. Properties of a solution are the following:

1. A solution is a homogeneous mixture.
2. The particles of a solution are smaller than 1 nm (10^-9 meter) in diameter. So, they cannot be seen by naked eyes.
3. Because of the very small particle size, they do not scatter a beam of light passing through the solution. So, the path of light is not visible in a solution.
4. The solute particles cannot be separated from the mixture by the process of filtration. The solute particles do not settle down when left undisturbed, that is, a solution is stable.

Ans. A solute is a component of a solution, which is dissolved in the solution. Its mass or volume is a very small fraction of the solution.

For example: In a cup of coffee, coffee seeds and sugar are the solutes.

Ans. A solvent is a component of a solution, which dissolves any solute. Its mass or volume is a large fraction of the solution.

Ans.A solution can be divided into three categories:

1. Saturated Solution
2. Unsaturated Solution
3. Supersaturated Solution

Ans. When no more solute can be dissolved in a solution at a given temperature, then the obtained solution is called a saturated solution.

Ans. When more solute can be dissolved in a solution at a given temperature, then the obtained solution is called an unsaturated solution.

Ans. Contains more dissolved solute than a saturated solution at the same temperature. This is an unstable state usually achieved by heating, allowing excess solute to dissolve, which may crystallize if disturbed.

Ans. Amount of the solute present in a saturated solution is called the solubility of the solution.

Solubility of a solution depends on types of solute, types of solvent and mostly on the temperature. By increasing the temperature of a solution, we can increase the solubility of the solution and vice versa. So, the temperature is directly proportional to the solubility of a solution.

Ans. The solubility of a solution depends on the following factors :-

1. The nature of the solute
2. The nature of the solvent
3. Temperature
4. Pressure

Ans. The amount of solute present per unit solution is called the concentration of the solution.

Dilute	Saturated Solution
Less amount of solute.	High amount of solute.
High amount of solvent.	Less amount of solvent.

Unsaturated	Saturated Solution
More solute can be dissolved.	No more solute can be dissolved.
Amount of solute is less than its solubility at a given temperature.	Amount of solute is equal to its solubility at a given temperature.

Formulas for finding the concentration of a given solution are:

1. Concentration of the solution = ^{Mass of solute}/_{Mass of solution} × 100
2. Concentration of the solution = ^{Mass of solute}/_{Volume of solution} × 100
3. Concentration of the solution = ^{Volume of solute}/_{Volume of solution} × 100

Ans.
Mass of Solute = 40 g
Mass of Solvent = 320 g

Hence, Mass of Solution = Mass of Solute + Mass of Solvent
= 40 + 320
= 360 g

Concentration of the solution = ^{Mass of solute}/_{Mass of solution} × 100

= (40 / 360) × 100
= 11.11%

Ans.
Mass of Solute = 36 g
Mass of Solvent = 100 g
Hence Mass of Solution = Mass of Solute + Mass of Solvent
= 36 + 100
= 136 g

Concentration of the solution = ^{Mass of solute}/_{Mass of solution} × 100

= (36 / 136) × 100
= 26.47%

Ans. Suspension is a heterogeneous mixture in which the solute particles do not dissolve; they remain suspended in the mixture and settle down when left undisturbed for some time.

Examples: muddy water, barley water, flour water etc.

Ans. Properties of a suspension are:

1. Suspension is a heterogeneous mixture.
2. The particles of a suspension can be seen by the naked eye.
3. The particles of a suspension scatter a beam of light passing through it and make its path visible.
4. The solute particles settle down when a suspension is left undisturbed, that is, a suspension is unstable. They can be separated from the mixture by the process of filtration. When the particles settle down, the suspension breaks and it does not scatter light anymore.

Ans. The effect in which the path of light is visible in a medium is called the Tyndall effect.

Ans. A colloid is a heterogeneous mixture but appears as a homogeneous mixture. The solute particles appear to be dissolved but they do not and do not settle down when left undisturbed for some time.

Example: milk

Ans. Properties of a colloidal are:

1. A colloid is a heterogeneous mixture.
2. The size of particles of a colloid is too small to be individually seen with naked eyes.
3. Colloids are big enough to scatter a beam of light passing through it and make its path visible.
4. They do not settle down when left undisturbed, that is, a colloid is quite stable and they cannot be separated from the mixture by the process of filtration.

Ans.Just like a solution, a colloidal has also two components but they are different from a solution and they are:

1. Disperesed Phase (like a solute )
2. Dispersion medium ( like a solvent )

Ans. The solute-like component or the dispersed particles in a colloid are called the dispersed phase.

Ans. The solvent-like component in which the dispersed phase is suspended is known as the dispersing medium.

Dispersed Phase	Dispersing Medium	Type	Example
Liquid	Gas	Aerosol	Fog, clouds, mist
Solid	Gas	Aerosol	Smoke, automobile exhaust
Gas	Liquid	Foam	Shaving cream
Liquid	Liquid	Emulsion	Milk, face cream
Solid	Liquid	Sol	Milk of magnesia, mud
Gas	Solid	Foam	Foam rubber, sponge, pumice
Liquid	Solid	Gel	Jelly, cheese, butter
Solid	Solid	Solid Sol	Coloured gemstone, milky glass

Colloidal	Solution	Suspension
A colloid is a heterogeneous mixture.	A solution is a homogeneous mixture.	Suspension is a heterogeneous mixture.
The size of particles of a colloid is too small to be individually seen with naked eyes.	The particles of a solution are smaller than 1 nm (10⁻⁹ m) in diameter, so they cannot be seen by naked eyes.	The particles of a suspension can be seen by the naked eye.
Colloids are big enough to scatter a beam of light passing through it and make its path visible.	Because of the very small particle size, they do not scatter a beam of light passing through the solution. So, the path of light is not visible in a solution.	The particles of a suspension scatter a beam of light passing through it and make its path visible. But when the particles settle down, the suspension breaks and it does not scatter light any more.
They do not settle down when left undisturbed, that is, a colloid is quite stable and they cannot be separated from the mixture by the process of filtration.	The solute particles cannot be separated from the mixture by the process of filtration. The solute particles do not settle down when left undisturbed, that is, a solution is stable.	The solute particles settle down when a suspension is left undisturbed, that is, a suspension is unstable. They can be separated from the mixture by the process of filtration.

Ans. There are various methods for separating the components of a mixture which depends on the types of the components of the mixture. For example:

1. Hand Picking
2. Winnowing
3. Threshing
4. Filtration
5. Magnetism
6. Evaporation
7. Centrifugation
8. Separating Funnel
9. Sublimation
10. Chromatography
11. Distillation
12. Fractional Distillation
13. Crystallisation

Ans. As the name suggests, hand picking is a method of separating solid components from a solid mixture by hands. If the solid components are big enough to be seen by the naked eyes, then this method is used.

Applications:

• Separating pebbles from rice
• Separating vegetables
• Separating books from a bulk

Ans. It is a method of separating solid components from a solid mixture by winds. If the mixture contains two solid components in which one is lighter, it can be winnowed by the wind and the other must be heavier.

Ans. It is a method of separating a solid component, which is attached to another solid component, by beating or shaking. If one lighter object is attached to the heavier object and the lighter object can be separated by beating or shaking, then this method is used.

Ans. It is a method of separating a suspended solid component from a liquid component by filtering. If the suspended component is as big as can be seen by the naked eyes then this method is used.

Ans. It is a method of separating magnetic materials from non-magnetic material by a magnet.

Ans. It is a method of separating volatile components from a non-volatile component in a solution by heating.

Ans. It is a method of separating a dispersed phase from a dispersing medium by spinning.

Ans. The principle of centrifugation is that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly.

Ans. Applications of the centrifugation are:

• Used in diagnostic laboratories for blood and urine tests.
• Used in dairies and homes to separate butter from cream.
• Used in washing machines to squeeze out water from wet clothes.

Ans. It is a method of separating a liquid from a mixture of another liquid but both the liquids must be immiscible.

Ans. The principle of the separating funnel method of separation is that immiscible liquids separate out in layers depending on their densities.

Ans. The applications of the separating funnel method of separation are:

• Used to separate a mixture of oil and water.
• In the extraction of iron from its ore, the lighter slag is removed from the top by this method to leave the molten iron at the bottom in the furnace.

Ans. It is a method of separating a sublimable component from a non-sublimable component by heating.

Ans. The principle of the sublimation method of separation is that sublimable components change directly from solid to gas by heating and can be separated easily from a non-sublimable component.

Ans. It is a method of separating the solutes which are dissolved in the same solvent but the rate of dissolving is different. This technique was first used for separation of colors, so this name was given.

Ans. The applications of the Chromatography method of separation are:

• To separate colors in a dye
• To separate pigments from natural colors
• To separate drugs from blood

Ans. It is a method of separating a liquid from the mixture of another liquid by heating when both are miscible and have different boiling points. Their boiling points must differ by more than 25 K.

Ans. It is a method of separating a liquid from the mixture of another liquid by heating when both are miscible and have different boiling points. Their boiling points must differ by less than 25 K.

Ans. It is a method of separating a solute from a solvent in the form of crystals by heating. It is similar to evaporation but better than it.

Ans. The Crystallisation method of separation is considered better than the Evaporation method of separation because of the following reasons:

• Some solids decompose or some, like sugar, may get charred on heating to dryness.
• Some impurities may remain dissolved in the solution even after filtration. On evaporation these contaminate the solid.

Ans. The applications of the Crystallisation method of separation are:

• Purification of salt that we get from sea water.
• Separation of crystals of alum (phitkari) from impure samples.

Ans. The following steps are used:

1. Sedimentation: Water from a water body is passed into a tank, also known as a sedimentation tank. In this tank, the water is left undisturbed for some time. All suspended particles settle down at the bottom.
2. Loading: From the sedimentation tank, water is passed into another tank, also known as a loading tank. This step helps the remaining suspended particles to settle down.
3. Filtration: From the loading tank, water is passed into a filtration tank containing fine sand, gravel and coarse gravel. Water is filtered through these layers.
4. Chlorination: From the filtration tank, water is passed into another tank where chlorine is added to kill bacteria and germs present in the water. This tank is called the chlorination tank.
5. Distribution: From the chlorination tank, the purified water is finally transported to towns and villages.

Ans. By the following activity, it can be confirmed:

The boiling point of water is 373 K (100°C) at 1 atmospheric pressure. If the given liquid starts boiling at 373 K (neither much before nor much after) and completely evaporates without leaving any residue, then the liquid is pure water.

Ans. A physical change is a type of change in which no new substance with different properties is formed. It is reversible.

Examples: Cutting of wood, melting of ice, change of state of matter, etc.

Ans. A chemical change is a type of change in which a new substance with different properties is formed. It is non-reversible.

Examples: Burning of wood, rusting, cooking of food, etc.

Ans. An element is the smallest part of any matter which cannot be further broken by even chemical reactions. There are a total of 118 known elements at present.

Ans. Elements are classified into four categories:

1. Metals
2. Nonmetals
3. Metalloids
4. Noble / Inert gases

Ans. Metals are lustrous, malleable, ductile, sonorous and good conductors of heat and electricity.

Examples: Iron, Copper, Gold, Silver, etc.

Ans. Nonmetals are non-lustrous, brittle, non-sonorous and poor conductors of heat and electricity.

Examples: Oxygen, Carbon, Hydrogen, etc.

Ans. Metalloids have some properties of metals as well as nonmetals.

Examples: Silicon, Boron, Germanium, etc.

Ans. Noble gases are non-reactive gases.

Examples: Helium, Neon, Argon, etc.

Ans. A compound is the smallest part of matter which can be broken into its constituents only by chemical reactions.

Or, a compound is matter composed of two or more atoms of the same or different kinds chemically bonded together in a fixed ratio.

Compound	Mixture
They are chemically bonded together.	They are not chemically bonded together.
Their constituents are in a fixed ratio.	Their constituents are not in a fixed ratio.
Their constituents cannot be separated by physical methods.	Their constituents can be separated by physical methods.
Formation of a compound is a chemical change.	Formation of a mixture is a physical change.
It does not show the properties of its constituents.	It shows the properties of its constituents.