NCERT Solutions Class 9 Science Ch 5 Mixtures 2026-27

• Muddy water is a suspension. Its particles are large and heavy, so they settle down on standing because of gravity.
• Milk is a colloid. Its particles are very small and stay evenly spread, so they do not settle down.

So the difference is due to the size of the particles and the nature of the mixture.

You see the rays because tiny particles in the air (dust and water droplets) scatter the light. This phenomenon is called the Tyndall effect, and it makes the path of the light visible.

1. FormulaMass of zinc oxide = (4 ÷ 100) × mass of the powder
2. CalculationZinc oxide = (4 ÷ 100) × 300 = 12 g

12 g of zinc oxide is present in 300 g of the powder.

1. Volume of concentrate2 × 15 = 30 mL
2. Total volume of the mixture150 mL
3. Volume percentage% (v/v) = (30 ÷ 150) × 100 = 20%

The orange juice concentrate is 20% v/v.

To prepare vinegar (5% v/v acetic acid) from glacial acetic acid (100%):

1. Take 5 mL of glacial acetic acid.
2. Add water to it to make the total volume 100 mL.

This gives a 5% v/v solution of acetic acid, which is vinegar.

Yes, the size of the crystals depends on the rate of evaporation.

• Fast evaporation forms small crystals.
• Slow evaporation forms large crystals.

Slow evaporation gives the particles more time to arrange themselves properly, so bigger crystals form. Fast evaporation makes the solid form quickly and irregularly, so smaller crystals form.

Correct answer: True

Salt does not evaporate. On evaporation the water leaves and the salt is left behind. In distillation the water is collected as the distillate and the salt remains in the flask.

Correct answer: False

Distillation works on the difference in boiling points. Liquids with the same boiling point turn into vapour together, so they cannot be separated by distillation.

Correct answer: False

The solvent level should be below the sample spot. If it were above, the spot would dissolve in the solvent instead of moving up the paper.

Correct answer: False

They are different processes. Crystallization gives pure solid crystals from a saturated solution, while evaporation may leave impurities behind along with the solid.

If two immiscible liquids have the same density, they will not form clear, separate layers. They may form an unstable mixture or an emulsion, which makes separation difficult or impossible with a separating funnel.

Reason: separation in a separating funnel depends on the difference in density, and here there is none.

Immiscible liquids form separate layers because:

• They do not dissolve in each other.
• They have different densities.

The denser liquid settles at the bottom and the lighter liquid stays on top, so two distinct layers form.

Yes, they are different.

They differ in the starting state of the substance and in the process.

Clouds are a colloid (an aerosol).

• They consist of tiny water droplets or ice crystals dispersed in air.
• The particles are small enough to stay suspended, and they do not settle down.
• They scatter light (they show the Tyndall effect).

Smoke and dust particles in the air scatter light. This scattering of light by tiny particles is the Tyndall effect, and it makes the atmosphere look foggy or hazy.

1. Mass of the solutionSolute (salt) = 10 g, solvent (water) = 90 gMass of solution = 10 + 90 = 100 g
2. Mass percentageMass % = (mass of solute ÷ mass of solution) × 100 = (10 ÷ 100) × 100 = 10%

10% m/m

1. GivenMass of glucose = 5 g, volume of solution = 100 mL
2. Mass by volume percentage(mass of solute ÷ volume of solution) × 100 = (5 ÷ 100) × 100 = 5%

5% m/v

1. GivenVolume of pesticide = 1 mL, total volume of solution = 100 mL
2. Volume percentage(volume of solute ÷ volume of solution) × 100 = (1 ÷ 100) × 100 = 1%

1% v/v

Correct option: (c)

A mixture is homogeneous if its composition is uniform throughout, and heterogeneous if it is not.

• (c) is correct: muddy water, milk and blood are heterogeneous, and brass is homogeneous.
• (a) is wrong: smoke is heterogeneous, not homogeneous.
• (b) is wrong: milk is heterogeneous, not homogeneous.
• (d) is wrong: brass and vinegar are homogeneous, and muddy water is heterogeneous.

Correct option: (d) a and c

The Tyndall effect is shown by mixtures whose particles are large enough to scatter light (colloids and suspensions), not by true solutions.

• Air and dust particles: shows the effect, because the dust particles are large enough to scatter light.
• Copper sulfate and water: does not show it, because this is a true solution with very small particles.
• Starch and water: shows the effect, because it is a colloid.
• Acetone and water: does not show it, because this is a true solution.

(i) Cake mix – use mass by mass percentage.

(ii) Brass (total mass = 120 g, copper = 70%)

(i) Sugar 15%, flour 84%, baking soda 1%    (ii) Copper 84 g, zinc 36 g

• Separate layer? Yes. Oil and water do not mix (they are immiscible), so they form two layers.
• Which is on top? The oil. One litre of oil has a mass of 910 g, so its density is 0.91 g/mL, which is less than that of water (1 g/mL). So oil floats on water.
• How to separate: use a separating funnel. Let the mixture settle, then open the stopcock and drain the lower water layer first. The oil remains in the funnel.

Correct option: (c)

• Assertion is true: the particles of a true solution are smaller than 1 nm, which is too small to scatter light, so no light path is seen.
• Reason is false: particles larger than 100 nm belong to colloids or suspensions, not to true solutions. The particles of a solution are much smaller.

Use distillation. The two liquids are miscible and their boiling points differ by 30°C. When the difference is more than about 25°C, simple distillation is enough. (If the difference is less than 25°C, fractional distillation is used.)

1. Heat the mixture in the distillation flask. Liquid A (60°C) has the lower boiling point, so it vaporises first.
2. The vapour passes into the condenser, where it cools and turns back into liquid.
3. Pure A is collected in the receiving flask while the thermometer reads about 60°C.
4. When the temperature rises to about 90°C, change the receiver and collect liquid B separately.

(i) If blood behaved like a true suspension, its particles would be large and unstable and would settle down because of gravity. The components of blood would separate inside the blood vessels, and the circulation of oxygen, nutrients and wastes would be disturbed.

(ii) Blood is a colloidal system, so:

• Dispersed phase: the blood cells (RBCs, WBCs and platelets).
• Dispersion medium: the plasma (the liquid part of the blood).

The correct sequence of the steps in Fig. b is 1 → 3 → 2.

1. Step 1: SublimationHeat the mixture under an inverted funnel. Naphthalene sublimes and is collected on the funnel, while sand and salt remain.
2. Step 3: Dissolving and filtrationAdd water to dissolve the salt, then filter. Sand stays on the filter paper as the residue.
3. Step 2: EvaporationHeat the filtrate in a china dish so that the water evaporates and the salt is left behind.

Sublimation → Dissolving in water and filtration → Evaporation

Water and acetone are miscible liquids with a large difference in boiling points (acetone about 56°C and water 100°C).

On heating, acetone (the lower boiling point) vaporises first. Its vapour is cooled and condensed to give pure acetone, while the water stays behind in the distillation flask. So the separation depends on the difference in boiling points, which makes distillation suitable and efficient for this mixture.

(i) At 40°C, 100 g of water dissolves 62 g of potassium nitrate. For 50 g of water:

(ii) At 80°C, 100 g of water dissolves 54 g of potassium chloride. At 25°C the solubility is only about 36 g (between 35 g at 20°C and 37.4 g at 30°C). As the solution cools its solubility decreases, so the extra salt (about 18 g for every 100 g of water) comes out of the solution. She will observe crystals of potassium chloride forming.

(iii) For most salts the solubility increases as the temperature increases. Comparing the salts from 10°C to 80°C:

Mass % = (mass of sugar ÷ mass of solution) × 100, where mass of solution = mass of sugar + mass of water.

(ii) Student C’s solution is the most concentrated.

It has the highest mass percentage of sugar, which means more solute is present for each unit mass of the solution.

(i) Technique S: distillation.

(ii) Apparatus: A – distillation flask (with the mixture, heated by the burner); B – condenser; C – receiving flask (where the distillate is collected).

(iii) Mixtures: distillation separates miscible liquids whose boiling points differ by more than about 25°C.

No, we cannot yet create artificial blood that works fully like real blood for all patients. Blood is a very complex colloidal mixture made of:

• Red blood cells (carry oxygen)
• White blood cells (fight infections)
• Platelets (help in clotting)
• Plasma (the transport medium)

Artificial substitutes (blood substitutes) can carry oxygen to some extent and can be used in emergencies. However, they cannot completely replace real blood because:

• they do not perform all the functions (such as immunity and clotting),
• they may have side effects, and
• they are usually only temporary solutions.