WorksheetsScience Quiz on Reactions and Mixtures
Total questions: 41
Worksheet time: 21mins
During the monsoon, Riya noticed her iron gate developed rust while copper pipes stayed shiny. What explains this?
Iron reacts more readily with oxygen and moisture than copper.
Copper reacts faster but forms invisible rust.
Both react equally, but copper is cleaned by rain.
Iron is heavier, so it rusts more easily.
A jeweler wants a metal that stays bright and doesn’t react with air. Which should he choose?
Aluminum – light and forms an oxide quickly.
Silver – shiny but easily tarnished.
Gold – least reactive and keeps its shine.
Iron – strong but rusts easily.
A candle burns brightly in oxygen but goes out in nitrogen. Why?
Oxygen supports combustion; nitrogen does not.
Nitrogen burns faster than oxygen.
Oxygen cools the flame.
Nitrogen has less energy.
A new element conducts electricity and can be stretched into wires. What type of element is it?
Metal
Non-metal
Metalloid
Noble gas
Arjun heated iron and sulfur together. The product couldn’t be separated by magnet. Why?
Iron lost its magnetism.
A new compound formed with different properties.
The mixture became denser.
Sulfur evaporated.
Maya boiled saltwater to get salt but couldn’t split water into hydrogen and oxygen the same way. Why?
Saltwater is a mixture; water is a compound.
Water boils at a lower temperature.
Salt evaporates before water.
Salt and water are both compounds.
Rina changes the amount of flour and sugar in cookies but uses fixed baking soda every time. Why is baking soda consistent?
It’s a compound with a fixed ratio of elements.
It reacts only with air.
It’s a pure element.
It changes with temperature.
Water sustains life, while carbon dioxide suffocates. Why, if both contain oxygen?
Their atoms are arranged differently, giving them unique properties.
Both have unstable bonds, but carbon is more harmful
2 atoms of Oxygen is present in CO₂.
CO₂ reacts with sunlight.
Milk looks uniform but scatters light. What kind of mixture is it?
Solution
Colloid
Suspension
Compound
When sugar dissolves in water, it forms—
A suspension with visible particles.
A homogeneous solution with uniform composition.
A colloid that settles over time.
A compound with new properties.
Fog and smoke both appear cloudy in air. How do they differ?
Fog has liquid droplets; smoke has solid particles.
Smoke has gas particles; fog does not.
Both are identical mixtures, but smoke is denser
Fog contains carbon while smoke does not
A teacher shows saltwater, milk, and muddy water. What property best classifies them?
Particle size in the mixture.
Color of liquid.
Taste and odor.
Temperature of formation.
When ice melts into water, what kind of change is it?
Physical – only state changes, not composition.
Chemical – new bonds form.
Reversible chemical reaction.
Permanent change.
Cooking changes the taste of vegetables. What kind of change is that?
Chemical change – new substances with different flavors form.
Physical change – water only evaporates.
No real change.
Temporary change.
When magnesium burns with a bright light, what happens?
Physical change only.
Chemical reaction forming magnesium oxide.
Dissolution in air.
Melting of magnesium.
A copper wire glows red-hot but cools back unchanged. This means—
Physical change due to heat energy.
Chemical oxidation.
Irreversible reaction.
New compound formed.
At a recycling center, how are metals usually separated from other waste?
By color difference.
By magnetism or conductivity.
By smell.
By dissolving in water.
A factory failed to sort materials before mixing and caused a chemical reaction. Why is sorting essential?
To prevent unwanted reactions and ensure correct processing.
To make the mixture colorful.
To reduce the temperature.
To increase quantity.
You are given a mix of sand, salt, and iron filings. What should you do first?
Use a magnet to remove iron filings.
Add water to dissolve salt.
Filter the whole mixture.
Heat it strongly.
An engineer selects materials for toys that bend without breaking. Which property matters most?
Flexibility and strength.
Color and shine.
Density.
Transparency.
To make muddy river water safe, which sequence is correct?
Sedimentation → Decantation → Filtration → Boiling.
Filtration → Boiling → Sedimentation.
Boiling → Sedimentation → Decantation.
Evaporation → Filtration.
A farmer uses a sieve to separate small stones from grains. What makes this possible?
Difference in particle size.
Color variation.
Weight difference only.
Magnetic property.
How can salt makers dry seawater faster?
Use wide shallow pans for more sunlight and evaporation.
Cover pans with glass lids.
Store in dark rooms.
Add ice to cool the mixture.
Why can’t salt and sand be separated by hand-picking?
Particles are too small and similar to distinguish.
Salt melts faster.
Sand dissolves easily.
Both are magnetic.
In an oil spill on sea water, which method works best?
Skimming or using a separating funnel since oil floats.
Boiling the mixture
Filtering through paper and decanting afterwards.
Freezing both liquids.
A farmer stored wheat mixed with pebbles after harvest. He wants to clean it before selling. Which method will work best and why?
Hand-picking, because pebbles and wheat differ in size and can be separated manually.
Filtration, because water can wash off the pebbles from the wheat grains.
Distillation, since pebbles will remain after water removal.
Magnetic separation, because metals are attracted to magnets.
In a mining site, workers collect a mixture of iron and sand. Which scientific property helps in separating them efficiently?
Magnetism, since iron is magnetic while sand is not.
Solubility, since iron dissolves faster in water.
Evaporation, as heating separates the two.
Winnowing, as sand is lighter than iron.
Maya collected sand containing bits of iron, shells, and salt crystals. Which sequence will best separate all three?
Magnetic separation → Filtration → Evaporation
Sieving → Magnetic separation → Dissolving and evaporation
Hand-picking → Condensation → Sublimation
Filtration → Sedimentation → Boiling
A cook accidentally mixes rice grains and salt. Which method can help recover both effectively?
Winnowing, as rice is heavier and settles faster in air.
Sieving, since rice grains are much larger than salt crystals.
Decantation, using water flow to remove salt.
Evaporation, to retain rice.
An archaeologist finds tiny gold dust mixed with sand. Which advanced technique can help?
Magnetic separation, since gold is slightly magnetic.
Winnowing, using air to blow away sand.
Density-based panning, as gold is denser and settles at bottom.
Evaporation, by heating the mixture.
A beaker of salt solution accidentally falls and mixes with sand. Which method can recover pure salt?
Filtration followed by evaporation
Winnowing, as sand will settle.
Sublimation, to turn salt into vapor.
Sedimentation, followed by distillation.
A spice company receives a batch containing powdered chili and larger coriander seeds. Which method is best?
Sieving, to allow fine chili powder to pass through while retaining seeds.
Density based separation, because chili is denser.
Hand-picking, which is faster.
Mix with water and then evaporation, to dry the mixture.
A teacher mixes ammonium chloride, sand, and salt as an experiment. What’s the correct order of separation?
Sublimation → Filtration → Evaporation
Evaporation → Filtration → Sublimation
Filtration → Sedimentation → Decantation
Winnowing → Sublimation → Evaporation
In a salt factory, workers find salt mixed with fine mud. How can they purify the salt efficiently?
Dissolve and sedimentation → Decant and Filter → Evaporate the mixture.
Sieve and Dissolve → Heat → Sublimate the salt.
Filter directly, since mud floats.
Use a magnet, as mud sticks to metal.
A paint company mixes pigment powder with water to make paint, but the particles keep settling. What does this indicate?
It’s a suspension, and can be separated by filtration.
It’s a solution, stable without separation.
It’s a colloid, which never settles.
It’s a compound, formed chemically.
In a chocolate factory, sugar crystals remain undissolved at the bottom of a syrup tank. What does this show?
The solution is saturated, and sugar can be separated by filtration.
Sugar has reacted chemically with syrup.
Sugar and syrup form a compound that is settling down.
The solution is unsaturated, needing more sugar.
A chemist wants to separate copper sulfate crystals from a blue liquid. Which method works best?
Evaporation, to remove the solvent and recover crystals.
Decantation, since crystals float.
Filtration, since both are solids.
Sublimation, since crystals vaporize easily.
Scientists filtering muddy water for astronauts on Mars find the filters clogging quickly. Which design improvement should they consider?
Use a two-step process — sedimentation first, then filtration
Heat before filtration, to evaporate mud.
Add oil, to trap dust.
Increase water pressure, to force
A salt-manufacturing plant uses open solar pans to evaporate seawater. After days of drying, impurities like dust and fine sand are seen with the salt.
Which modification would improve purity without using extra chemicals?
Install fans to speed up evaporation, as faster drying prevents impurity deposition.
Use filtration before evaporation, so insoluble solids don’t remain in the final salt.
Add bleaching powder to remove impurities chemically.
Cover the pans with plastic sheets to stop air circulation.
A recycling plant separates steel parts, aluminum cans, and plastic bottles on a conveyor belt.
Hint: Non-magnetic metals like aluminum can be separated using tiny currents induced when they pass through a changing magnetic field.
Which sequence is most practical?
Magnetic separator → Eddy-current separator
Optical sensor → Eddy-current separator
Eddy-current separator → Magnetic separator → Air jet
Filtration → Evaporation → Condensation
A biotechnology lab needs to separate bacterial cells from a nutrient solution without killing the microbes.
Which process should be used?
Filtration using microporous membranes, allowing only liquid nutrients to pass retaining all solids
Centrifugation, which uses density to settle cells gently.
Distillation, to dry out and collect bacteria.
Magnetic separation, since bacteria are metallic in nature.
