Nature of Matter: Elements, Compounds, and Mixtures are important concepts in chemistry. This chapter explains the difference between mixtures, pure substances, elements, and compounds. It also shows how substances behave differently when they are only mixed and when they combine chemically.
The MCQs and match-the-following questions for Chapter 8 cover key topics like mixtures, uniform and non-uniform mixtures, pure substances, elements, compounds, electrolysis of water, iron and sulfur experiment, alloys, minerals, and uses of elements, compounds, and mixtures. The questions are created to test your understanding and prepare you for exams. Solving these will help you remember key facts and concepts quickly.
Please check MCQ for other chapters Class 8 Science MCQ Questions and Answers.
Class 8 Science Chapter 8 MCQ Online Test Questions and Answers
Question 1. A mixture is formed when two or more substances are combined in such a way that:
a) They always form a new substance
b) Each substance retains its properties
c) The substances must be gases only
d) The substances cannot be separated at all
Answer:
b) Each substance retains its properties
Question 2. The individual substances that make up a mixture are called its:
a) Molecules
b) Components
c) Elements
d) Atoms
Answer:
b) Components
Question 3. In a mixture, the components do not react chemically with each other. This means:
a) A new substance is always formed
b) The properties of the original substances remain unchanged
c) The substances lose their identity completely
d) The mixture becomes a pure substance
Answer:
b) The properties of the original substances remain unchanged
Question 4. A sprout salad is considered a non-uniform mixture because its components are:
a) Chemically combined
b) Evenly distributed throughout
c) Visible separately
d) Made only of liquids
Answer:
c) Visible separately
Question 5. Sugar dissolved in water is called a uniform mixture because:
a) The sugar reacts chemically with water
b) The sugar particles can still be seen clearly
c) The components are evenly distributed and cannot be distinguished
d) The mixture contains only one substance
Answer:
c) The components are evenly distributed and cannot be distinguished
Question 6. Air is classified as a:
a) Non-uniform mixture
b) Uniform mixture
c) Compound
d) Pure element
Answer:
b) Uniform mixture
Question 7. Which of the following gases makes up about 78% of air?
a) Oxygen
b) Carbon dioxide
c) Nitrogen
d) Argon
Answer:
c) Nitrogen
Question 8. Oxygen in air is important mainly because it:
a) Prevents combustion
b) Supports respiration and combustion
c) Makes air uniform
d) Gives air its colour
Answer:
b) Supports respiration and combustion
Question 9. When warm air touches a cool surface, the water vapour present in air changes into:
a) Smoke
b) Ice crystals only
c) Tiny liquid water droplets
d) Carbon dioxide
Answer:
c) Tiny liquid water droplets
Question 10. Lime water turns milky when exposed to air because carbon dioxide reacts with calcium hydroxide to form:
a) Calcium oxide
b) Calcium carbonate
c) Calcium chloride
d) Calcium sulfate
Answer:
b) Calcium carbonate
Question 11. The turning of lime water milky demonstrates the presence of which gas in air?
a) Oxygen
b) Nitrogen
c) Carbon dioxide
d) Hydrogen
Answer:
c) Carbon dioxide
Question 12. Dust particles suspended in air are considered:
a) Essential components of air
b) Pollutants
c) Pure substances
d) Compounds of air
Answer:
b) Pollutants
Question 13. In science, all the components of a mixture must be:
a) Visible to the naked eye
b) Pure substances
c) Liquids only
d) Gases only
Answer:
b) Pure substances
Question 14. Which of the following is a uniform mixture?
a) Sand and water
b) Oil and water
c) Vinegar
d) Sprout salad
Answer:
c) Vinegar
Question 15. Which of the following is a non-uniform mixture?
a) Air
b) Seawater
c) Aerated water
d) Carbon particles in air
Answer:
d) Carbon particles in air
Question 16. In common usage, the word “pure” usually means:
a) A substance containing only one type of particle
b) A substance that cannot be separated physically
c) An unadulterated product
d) A chemical compound only
Answer:
c) An unadulterated product
Question 17. In science, a pure substance is one that:
a) Contains at least two substances mixed evenly
b) Has no other substance present in it
c) Is always a liquid
d) Can be separated by filtration
Answer:
b) Has no other substance present in it
Question 18. A pure substance cannot be separated into other kinds of matter by any:
a) Chemical process
b) Physical process
c) Heating process
d) Natural process
Answer:
b) Physical process
Question 19. When electricity is passed through water, the gases formed are:
a) Nitrogen and oxygen
b) Hydrogen and oxygen
c) Hydrogen and carbon dioxide
d) Oxygen and chlorine
Answer:
b) Hydrogen and oxygen
Question 20. In the electrolysis of water, the gas that burns with a pop sound is:
a) Oxygen
b) Nitrogen
c) Hydrogen
d) Carbon dioxide
Answer:
c) Hydrogen
Question 21. During the electrolysis of water, the gas that makes a candle flame glow brighter is:
a) Hydrogen
b) Oxygen
c) Water vapour
d) Nitrogen
Answer:
b) Oxygen
Question 22. Water is considered a compound because hydrogen and oxygen in it are:
a) Mixed physically in any ratio
b) Combined chemically in a fixed ratio
c) Visible separately
d) Easily separated by filtration
Answer:
b) Combined chemically in a fixed ratio
Question 23. The ratio of hydrogen atoms to oxygen atoms in water is:
a) 1:1
b) 1:2
c) 2:1
d) 3:1
Answer:
c) 2:1
Question 24. Elements are substances that:
a) Can always be broken down into simpler substances
b) Cannot be further broken down into simpler substances
c) Are always gases
d) Are always compounds
Answer:
b) Cannot be further broken down into simpler substances
Question 25. The identical particles that make up an element are called:
a) Mixtures
b) Components
c) Atoms
d) Solutions
Answer:
c) Atoms
Question 26. Two or more atoms of an element may combine to form a stable particle called a:
a) Compound
b) Molecule
c) Mixture
d) Mineral
Answer:
b) Molecule
Question 27. Which of the following is a metal?
a) Oxygen
b) Hydrogen
c) Sulfur
d) Aluminium
Answer:
d) Aluminium
Question 28. Which of the following is a non-metal?
a) Gold
b) Iron
c) Carbon
d) Magnesium
Answer:
c) Carbon
Question 29. On heating sugar, the black substance left behind in the boiling tube is:
a) Sulfur
b) Charcoal or carbon
c) Iron oxide
d) Calcium carbonate
Answer:
b) Charcoal or carbon
Question 30. Sugar is a compound made of the elements:
a) Sodium, chlorine, and oxygen
b) Carbon, hydrogen, and oxygen
c) Nitrogen, hydrogen, and oxygen
d) Carbon, sulfur, and oxygen
Answer:
b) Carbon, hydrogen, and oxygen
Question 31. Sample A in the iron-sulfur experiment is a mixture because:
a) It has uniform colour and texture throughout
b) Iron and sulfur lose all their original properties
c) Its components retain their properties and can be separated
d) It cannot be affected by a magnet
Answer:
c) Its components retain their properties and can be separated
Question 32. Sample B formed by heating iron and sulfur is:
a) A uniform mixture
b) A compound called iron sulfide
c) Pure sulfur
d) Pure iron
Answer:
b) A compound called iron sulfide
Question 33. When dilute hydrochloric acid is added to Sample A, the gas evolved is:
a) Hydrogen sulfide
b) Oxygen
c) Hydrogen
d) Carbon dioxide
Answer:
c) Hydrogen
Question 34. When dilute hydrochloric acid is added to Sample B, the gas evolved has a rotten egg-like smell because it is:
a) Hydrogen
b) Hydrogen sulfide
c) Oxygen
d) Nitrogen dioxide
Answer:
b) Hydrogen sulfide
Question 35 – Match the Following
| Column A | Column B |
|---|---|
| 1. Uniform mixture | A. Components visible separately |
| 2. Non-uniform mixture | B. Same type of particles only |
| 3. Pure substance | C. Components evenly distributed |
| 4. Element | D. Cannot be broken into simpler substances |
| 5. Compound | E. Different elements combined in fixed ratio |
Answer:
| Column A | Correct Answer |
|---|---|
| 1. Uniform mixture | C. Components evenly distributed |
| 2. Non-uniform mixture | A. Components visible separately |
| 3. Pure substance | B. Same type of particles only |
| 4. Element | D. Cannot be broken into simpler substances |
| 5. Compound | E. Different elements combined in fixed ratio |
Question 36 – Match the Following
| Column A | Column B |
|---|---|
| 1. Lime water | A. Burns with pop sound |
| 2. Hydrogen gas | B. Turns milky in presence of carbon dioxide |
| 3. Oxygen gas | C. Glows brighter with burning candle |
| 4. Sample A | D. Mixture of iron and sulfur |
| 5. Sample B | E. Compound iron sulfide |
Answer:
| Column A | Correct Answer |
|---|---|
| 1. Lime water | B. Turns milky in presence of carbon dioxide |
| 2. Hydrogen gas | A. Burns with pop sound |
| 3. Oxygen gas | C. Glows brighter with burning candle |
| 4. Sample A | D. Mixture of iron and sulfur |
| 5. Sample B | E. Compound iron sulfide |
