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Substances & Their Composition — Homi Bhabha Class 6 Chemistry MCQs with Solutions
Free Homi Bhabha Class 6 Chemistry Substances & Their Composition MCQs with step-by-step solutions covering Pure Substances, Elements & Compounds, Mixtures & Solutions, Suspensions & Colloids. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Pure Substances · easy · theory
Which of these is a pure substance?
A. Milk
B. Garden soil
C. Lemonade
D. Distilled water ✓ Correct
Solution: Distilled water is made of only one kind of particle (H₂O), so it is a pure substance. Lemonade, soil and milk are mixtures of many things.
Q2 — Pure Substances · easy · theory
A pure substance is made up of only one kind of ______.
A. shape
B. colour
C. size
D. particle ✓ Correct
Solution: A pure substance contains only one kind of particle throughout, which gives it the same composition everywhere.
Q3 — Pure Substances · easy · theory
Which of the following is a pure substance?
A. Air
B. Vegetable soup
C. Pure gold ✓ Correct
D. Sea water
Solution: Pure gold is made of only gold, so it is a pure substance. Sea water, air and soup are all mixtures of different substances.
Q4 — Pure Substances · easy · theory
Table salt is called a pure substance because it ______.
A. can be split into water and sugar
B. has the same composition throughout ✓ Correct
C. is a mixture of many salts
D. keeps changing its composition
Solution: Every part of pure table salt is the same, so it has a fixed composition throughout — that is what makes it a pure substance.
Q5 — Elements & Compounds · easy · theory
An element is made up of only one kind of ______.
A. atom ✓ Correct
B. solution
C. mixture
D. compound
Solution: An element contains only one kind of atom, so it cannot be broken down into any simpler substance.
Q6 — Elements & Compounds · easy · theory
Which of these is an element?
A. Oxygen (O₂) ✓ Correct
B. Salt (NaCl)
C. Water (H₂O)
D. Sugar
Solution: Oxygen is made of only oxygen atoms, so it is an element. Water, salt and sugar are compounds made of more than one element.
Q7 — Elements & Compounds · easy · theory
Water (H₂O) is an example of a ______.
A. element
B. metal
C. mixture
D. compound ✓ Correct
Solution: Water is made of two elements, hydrogen and oxygen, joined chemically in a fixed ratio, so it is a compound.
Q8 — Elements & Compounds · easy · theory
Which of the following is a compound?
A. Gold
B. Carbon dioxide (CO₂) ✓ Correct
C. Iron
D. Hydrogen
Solution: Carbon dioxide is made of carbon and oxygen joined together, so it is a compound. Gold, iron and hydrogen are elements.
Q9 — Mixtures & Solutions · easy · theory
A mixture in which the substances are completely mixed and look the same throughout is called a ______.
A. compound
B. suspension
C. solution ✓ Correct
D. element
Solution: A solution is a mixture that is uniform (the same) throughout, like sugar fully dissolved in water.
Q10 — Mixtures & Solutions · easy · theory
When you dissolve sugar in water, the sugar is the ______.
A. solution
B. gas
C. solvent
D. solute ✓ Correct
Solution: The substance that dissolves is called the solute, so here the sugar is the solute and the water is the solvent.
Q11 — Mixtures & Solutions · easy · theory
In a salt solution, water is the ______.
A. element
B. solute
C. precipitate
D. solvent ✓ Correct
Solution: The liquid that does the dissolving is the solvent. Water dissolves the salt, so water is the solvent.
Q12 — Mixtures & Solutions · easy · theory
Which of these is a mixture?
A. Pure gold
B. Air ✓ Correct
C. Oxygen
D. Distilled water
Solution: Air is a mixture of several gases such as nitrogen and oxygen. The others are pure substances.
Q13 — Suspensions & Colloids · easy · theory
In a suspension, the solid particles slowly ______.
A. turn into gas
B. float and never settle
C. settle down at the bottom ✓ Correct
D. disappear completely
Solution: A suspension has large particles that do not dissolve, so on standing they slowly sink and settle at the bottom.
Q14 — Suspensions & Colloids · easy · theory
Which of these is an example of a suspension?
A. Sugar solution
B. Salt water
C. Distilled water
D. Muddy water ✓ Correct
Solution: In muddy water the mud particles are large, stay undissolved and settle down — that makes it a suspension.
Q15 — Suspensions & Colloids · easy · theory
Which of these is a common example of a colloid?
A. Table salt
B. Oxygen gas
C. Pure water
D. Milk ✓ Correct
Solution: Milk looks cloudy and its tiny particles stay spread out without settling, which makes it a colloid.
Q16 — Suspensions & Colloids · easy · theory
The particles in a suspension are ______.
A. large enough to be seen ✓ Correct
B. always dissolved
C. made of gas only
D. too small to be seen
Solution: Suspension particles are big — often big enough to see — which is why they do not dissolve and can be filtered out.
Q17 — Pure Substances · hard · theory
Which set contains ONLY pure substances?
A. Gold, oxygen and distilled water ✓ Correct
B. Brass, water and diamond
C. Salt water, sugar and iron
D. Milk, gold and air
Solution: Gold, oxygen and distilled water are all pure. The other sets include mixtures — milk, air, salt water and brass (a mix of metals) are not pure.
Q18 — Pure Substances · hard · theory
Ravi has a shiny yellow metal. It melts at one fixed temperature and cannot be broken down into simpler substances by any physical method. The metal is most likely ______.
A. a mixture of metals
B. brass
C. muddy water
D. pure gold, a pure substance ✓ Correct
Solution: A fixed melting point and being impossible to separate physically are signs of a pure substance, so the metal is most likely pure gold.
Q19 — Elements & Compounds · hard · theory
Which list contains ONLY elements?
A. Hydrogen, water and oxygen
B. Carbon, sugar and gold
C. Iron, oxygen and gold ✓ Correct
D. Water, iron and salt
Solution: Iron, oxygen and gold are all made of one kind of atom, so all are elements. The other lists include compounds like water, salt and sugar.
Q20 — Elements & Compounds · hard · theory
Table salt (NaCl) is made of sodium, a soft metal, and chlorine, a poisonous gas — yet salt is safe to eat. This is because in a compound ______.
A. salt is only a loose mixture of the two
B. no chemical change takes place
C. the elements form a new substance with new properties ✓ Correct
D. the elements keep their own properties
Solution: When elements combine into a compound, a completely new substance forms with new properties, so salt is nothing like sodium or chlorine on their own.
Q21 — Mixtures & Solutions · hard · theory
Which method would you use to get pure salt back from salt water?
A. Use a magnet
B. Evaporate the water ✓ Correct
C. Filter the solution
D. Add more water
Solution: The salt is dissolved, so a filter will not stop it. Heating the water makes it evaporate and leaves the solid salt behind.
Q22 — Mixtures & Solutions · hard · theory
A homogeneous mixture looks the same throughout, while a heterogeneous mixture does not. Which of these is a heterogeneous mixture?
A. A bowl of vegetable salad ✓ Correct
B. Sugar dissolved in tea
C. Salt water
D. Air
Solution: In a vegetable salad you can clearly see the different pieces, so it is heterogeneous. The others look the same throughout, so they are homogeneous.
Q23 — Suspensions & Colloids · hard · theory
Fog is tiny water droplets spread in air, and it scatters the light from a car’s headlights. Fog is an example of a ______.
A. pure substance
B. suspension that settles quickly
C. colloid ✓ Correct
D. true solution
Solution: Fog is a colloid — its tiny droplets stay spread in the air without settling and scatter light, which is why headlights glow in fog.
Q24 — Suspensions & Colloids · hard · theory
Three glasses contain: (1) sugar water — clear, (2) muddy water — particles settle, (3) milk — cloudy, particles do not settle. Which match is correct?
A. 1 suspension, 2 colloid, 3 solution
B. 1 solution, 2 suspension, 3 colloid ✓ Correct
C. 1 solution, 2 colloid, 3 suspension
D. 1 colloid, 2 solution, 3 suspension
Solution: Clear sugar water is a solution, muddy water whose particles settle is a suspension, and cloudy milk whose particles stay spread is a colloid.
Q25 — Pure Substances · medium · theory
Which property is TRUE for a pure substance?
A. It has a fixed melting and boiling point ✓ Correct
B. It has no fixed melting point
C. It always contains water
D. It is always a liquid
Solution: A pure substance always melts and boils at fixed temperatures. A mixture usually does not have a single fixed melting or boiling point.
Q26 — Pure Substances · medium · theory
Distilled water boils at exactly 100°C at sea level, but sea water boils at a slightly higher temperature. This shows that ______.
A. both are pure substances
B. water is never a pure substance
C. sea water is purer than distilled water
D. distilled water is pure while sea water is a mixture ✓ Correct
Solution: A pure substance boils at one fixed temperature. The salt dissolved in sea water changes its boiling point, showing sea water is a mixture.
Q27 — Pure Substances · medium · theory
Which one of these is NOT a pure substance?
A. Orange juice ✓ Correct
B. Diamond
C. Oxygen gas
D. Copper
Solution: Orange juice is a mixture of water, sugars, acids and pulp. Diamond, copper and oxygen are each made of only one kind of particle.
Q28 — Pure Substances · medium · theory
Sugar taken from a sugar packet is a pure substance mainly because ______.
A. it is white in colour
B. every grain has the same composition ✓ Correct
C. it tastes sweet
D. it dissolves in water
Solution: Being sweet, white or able to dissolve are just properties. It is called pure because every grain has exactly the same composition.
Q29 — Elements & Compounds · medium · theory
A compound is formed when two or more elements ______.
A. are the same kind of atom
B. are placed side by side
C. are simply mixed together
D. combine chemically in a fixed ratio ✓ Correct
Solution: In a compound the elements join by a chemical change in a fixed ratio, forming a new substance — not just a loose mixture.
Q30 — Elements & Compounds · medium · theory
Which statement about an element is correct?
A. It can be separated by filtering
B. It contains two different kinds of atoms
C. It cannot be broken down into simpler substances by chemical means ✓ Correct
D. It is always a mixture
Solution: An element is the simplest form of matter and cannot be broken down into anything simpler by ordinary chemical methods.