Exploring Mixtures and Their Separation

Mud particles are large and heavy, so they settle under gravity. Milk is a colloid: its tiny droplets stay spread through the liquid and do not settle easily.

Evaporation happens at the surface and can happen below the boiling point. Boiling happens throughout the liquid at its boiling point, with bubbles forming.

Dust and tiny particles in the air scatter the sunlight. This scattering makes the light path visible; it is the Tyndall effect.

Salt water is a clear solution: particles are invisible, do not settle, do not scatter the beam, and pass through filter paper. Chalk water is a suspension: particles are visible, settle, scatter light, and leave residue on the filter. Milk water is a colloid: particles are not visible, do not settle, scatter light, and usually pass through ordinary filter paper.

Mass of zinc oxide = 4/100 × 300 g = 12 g.

Concentrate volume = 2 × 15 = 30 mL. Percentage = 30/150 × 100 = 20% v/v.

Use 5 mL of pure acetic acid and add water until the total solution volume is 100 mL. Always add acid carefully to water, with adult or teacher supervision.

B is more soluble at all shown temperatures. A’s solubility increases more steeply as temperature rises.

With teacher supervision, gently heat water and dissolve copper sulfate until the solution is saturated. Filter it while hot, leave it covered to cool slowly, then collect and dry the crystals. Copper sulfate is harmful; do not touch it or taste it.

Water evaporates and blue crystals may remain. It can show crystal formation, but it is not ideal for making clean, well-shaped crystals because evaporation is fast and dust or impurities can mix in.

Prepare one hot saturated solution and divide equal amounts into two identical containers. Cool one slowly at room temperature and the other quickly in an ice bath. Keep volume, concentration, and containers the same. Compare crystal size and shape after the same time; repeat for reliability. Teacher supervision is required.

B deposits about 15.9 g per 100 g solution; A about 6.0 g.

Slow evaporation gives particles more time to arrange into larger crystals. Fast evaporation usually produces smaller crystals.

Seawater is collected in shallow ponds. Sun and wind evaporate much of the water, making concentrated brine. The remaining water evaporates further and salt crystals form; workers collect and dry them.

Use distillation. Heat the salt solution so water evaporates, cool the water vapour in a condenser, and collect the liquid water. Salt remains in the flask.

Use distillation because acetone boils at about 56°C and water at 100°C. Acetone vapour forms first and can be condensed and collected. Simple evaporation would lose the vapour, so it would not recover both liquids.

The ink contains several dyes. The solvent carries each dye at a different rate because each interacts differently with the paper and solvent, so the colours separate.

(1) True: evaporation leaves salt; distillation can recover water. (2) False: simple distillation does not separate liquids with the same boiling point effectively. (3) False: solvent level must start below the ink spot. (4) False: evaporation removes solvent; crystallisation forms purer solid crystals from a solution.

They form layers because they do not mix. Water is denser and settles at the bottom; oil floats above it. Open the tap to drain water first, close it at the boundary, then collect the oil separately.

They may not form clearly separate top and bottom layers, so a separating funnel based on density will not separate them well. Another property or method is needed.

Camphor changes directly from solid to vapour and deposits as a solid on the cool funnel. Sand does not sublime and stays in the dish. Use teacher supervision and safe heating.

They do not dissolve in each other. The denser liquid settles below the less dense liquid, forming two layers.

Yes. Sublimation changes a solid directly into gas without becoming liquid. Evaporation changes a liquid into gas from its surface.

When spun, heavier particles in a suitable mixture move outward and separate from lighter liquid. A safe classroom example is muddy water in sealed containers; do not use biological samples.

Alum makes fine suspended particles clump together. The heavier clumps settle; the clearer water can then be carefully decanted or filtered. This water is not automatically safe to drink.

Blood has dispersed particles that are too small to see without help and stay distributed for a time, like a colloid. Its components can still be separated by centrifugation.

Clouds are colloids: tiny water droplets or ice crystals are dispersed through air and scatter light.

Smoke and dust particles scatter light in many directions. This scattering reduces clear visibility and makes the air look hazy.

Solution: homogeneous; particles <1 nm; transparent and not visible; not separated by ordinary filtration; do not settle; no Tyndall effect. Suspension: heterogeneous; particles >1000 nm; often visible; can be filtered; settle; show Tyndall effect. Colloid: heterogeneous though it may look uniform; particles 1–1000 nm; not visible individually; not separated by ordinary filtration; do not settle; show Tyndall effect.

Option (iv): muddy water, milk, and blood are heterogeneous; brass is homogeneous.

Air with dust and starch water show the effect. Their particles scatter light. Correct choice: (iii), a and c. The two clear solutions do not show it.

Solution: tiny particles (<1 nm), transparent, do not settle, cannot be separated by filtration; examples salt solution and brass. Suspension: large particles (>1000 nm), settles, scatters light, can be filtered; examples sand in water and mud. Colloid: medium particles (1–1000 nm), stays dispersed, scatters light, not separated by ordinary filtration; examples milk, smoke, and butter.

Total mass = 75 + 420 + 5 = 500 g. Sugar = 75/500 × 100 = 15% m/m. Flour = 420/500 × 100 = 84% m/m. Sodium hydrogencarbonate = 5/500 × 100 = 1% m/m.

Copper = 70/100 × 120 = 84 g. Zinc is the remaining 30%: 120 − 84 = 36 g.

Yes. Oil and water are immiscible. Oil density is 0.91 g/mL, less than water’s about 1 g/mL, so oil floats. Use a separating funnel: drain the lower water layer, then collect the oil.

Option (iii): A is true, R is false. Solution particles are very small (less than 1 nm), not larger than 100 nm, and do not scatter visible light.

Mud/water: coagulation then settling/filtration, because fine particles need clumping. Plasma/blood: centrifugation, based on density. Naphthalene/sand: sublimation. Chalk/salt: dissolve salt in water, filter chalk, then evaporate or crystallise salt. Salt/water: distillation to recover both, or evaporation for salt only. Oil/water: separating funnel. Flower pigments: paper chromatography.

Use simple distillation because the boiling points differ by 30°C. Heat the mixture; A vaporises first. Pass its vapour through a water-cooled condenser and collect A. B remains in the flask. Label a diagram with flask and mixture, heat source, thermometer, condenser, cooling-water inlet/outlet, and receiver.

Evaporation removes solvent and leaves dissolved solid; use it when only the solid is needed. Crystallisation forms purer solid crystals from a saturated solution; use it to purify a solid. Distillation evaporates then condenses vapour; use it to recover solvent or separate liquids with different boiling points.

Large particles might settle and block vessels, disrupting blood flow. In blood, the dispersed phase includes blood cells and other particles; the dispersion medium is plasma.

First heat gently: naphthalene sublimes and can be collected on a cool surface. Add water to the remaining sand and salt: salt dissolves, sand does not. Filter out sand, then evaporate or crystallise the salt solution.

Their boiling points differ: acetone boils near 56°C and water near 100°C. Acetone vaporises first and can be cooled and collected separately.

At 40°C, solubility is 62 g per 100 g water. For 50 g water: 62 × 50/100 = 31 g.

At 80°C, 54 g dissolves per 100 g water. At 25°C, the value is about 36 g (between 20°C and 30°C). About 18 g per 100 g water crystallises out as the solution cools.

Their solubility increases as temperature rises, but by different amounts. From 10°C to 80°C: potassium nitrate rises by 146 g/100 g water; sodium chloride by 1 g; potassium chloride by 19 g; ammonium chloride by 42 g. Potassium nitrate changes most; sodium chloride least.

A: 20/100 × 100 = 20%. B: 20/120 × 100 ≈ 16.7%. C: 30/110 × 100 ≈ 27.3%. C is most concentrated because it has the highest sugar percentage.

S is fractional distillation. A: flask with mixture; B: fractionating column; C: condenser. It can separate acetone–alcohol, alcohol–chloroform, and alcohol–benzene because their boiling points are close.

Use a flashlight in a dim room and shine it through clear water, diluted milk, and dusty air (avoid making dust). The beam path is clearer in colloids because particles scatter light. Never look into a laser; use adult supervision.

With teacher supervision, prepare saturated solutions of safe substances such as salt or sugar, let them evaporate slowly, then observe crystal shape and colour with a magnifier. Record substance, method, and observations. Do not handle toxic salts.

Crush a red leaf with a small amount of suitable solvent. Put a small extract spot on a pencil line on chromatography paper, with solvent below the spot. Let the solvent rise. Separate coloured bands show different pigments; a green band indicates green pigment is present.

Place a tiny sample on a pencil baseline of paper and stand the strip in a suitable solvent with the solvent below the spot. As the solvent rises, different components travel different distances and form separate spots. Count the spots to estimate the number of components.

Make cards naming mixtures and method cards such as filtration, distillation, chromatography, and sublimation. Players match each mixture to a method and explain the property used. Award a point for a correct match and reason.

Place salty or unsafe water in a covered pot and guide the vapour to a clean, cool surface or tube where it condenses into a clean container. Keep the collection vessel separate from the original water. Distillation removes many dissolved substances but does not guarantee every contaminant is removed.