NCERT Class 8 Science MCQ | Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures
1. What is a mixture?
(A) A substance made of only one type of particle
(B) Two or more substances mixed together in which each retains its properties
(C) A substance formed only by a chemical reaction
(D) A substance that cannot be separated
Answer: (B) Two or more substances mixed together in which each retains its properties
2. What are the individual substances that make up a mixture called?
(A) Elements
(B) Components
(C) Compounds
(D) Molecules
Answer: (B) Components
3. Which statement about the components of a mixture is correct?
(A) They always react chemically with each other
(B) They lose all their individual properties
(C) They do not react chemically with each other
(D) They always combine in a fixed ratio
Answer: (C) They do not react chemically with each other
4. Which of the following is a non-uniform mixture?
(A) Sugar dissolved in water
(B) Air
(C) Sprout salad
(D) Salt solution
Answer: (C) Sprout salad
5. What is a uniform mixture?
(A) A mixture in which components are evenly distributed and cannot be distinguished
(B) A mixture in which all components are clearly visible
(C) A mixture containing only solids
(D) A mixture formed by a chemical reaction
Answer: (A) A mixture in which components are evenly distributed and cannot be distinguished
6. Which of the following is a uniform mixture?
(A) Sand and water
(B) Oil and water
(C) Sugar and water
(D) Sprout salad
Answer: (C) Sugar and water
7. Why is air considered a mixture?
(A) It contains only oxygen
(B) It contains several gases that are mixed without undergoing chemical combination
(C) All gases in air form a compound
(D) Air has only one type of particle
Answer: (B) It contains several gases that are mixed without undergoing chemical combination
8. Approximately what percentage of air is nitrogen?
(A) 21%
(B) 50%
(C) 78%
(D) 90%
Answer: (C) 78%
9. Which of the following is an alloy?
(A) Oxygen
(B) Brass
(C) Water
(D) Carbon dioxide
Answer: (B) Brass
10. Brass is a mixture of:
(A) Copper and tin
(B) Iron and carbon
(C) Copper and zinc
(D) Iron and sulfur
Answer: (C) Copper and zinc
11. What happens when lime water is exposed to carbon dioxide present in air?
(A) It becomes blue
(B) It turns milky
(C) It becomes solid immediately
(D) It turns green
Answer: (B) It turns milky
12. Why does lime water turn milky in the presence of carbon dioxide?
(A) Calcium hydroxide reacts with carbon dioxide to form insoluble calcium carbonate
(B) Water evaporates from the solution
(C) Oxygen reacts with calcium hydroxide
(D) Nitrogen dissolves in lime water
Answer: (A) Calcium hydroxide reacts with carbon dioxide to form insoluble calcium carbonate
13. What do dust particles suspended in air represent?
(A) Pure substances
(B) Air pollutants
(C) Elements only
(D) Compounds only
Answer: (B) Air pollutants
14. Which of the following is a pure substance according to the scientific definition?
(A) Air
(B) Seawater
(C) Sugar
(D) Soil
Answer: (C) Sugar
15. What is a pure substance?
(A) Matter containing several substances mixed together
(B) Matter consisting of the same type of particles
(C) Any substance that looks clean
(D) Any substance that can be separated by filtration
Answer: (B) Matter consisting of the same type of particles
16. Which two types of substances are classified as pure substances?
(A) Elements and compounds
(B) Mixtures and alloys
(C) Uniform and non-uniform mixtures
(D) Solids and liquids
Answer: (A) Elements and compounds
17. What is an element?
(A) A substance that can be separated into simpler substances by physical methods
(B) A pure substance that cannot be broken down into simpler substances
(C) A mixture of two or more substances
(D) A substance containing several compounds
Answer: (B) A pure substance that cannot be broken down into simpler substances
18. The particles of an element are called:
(A) Compounds
(B) Atoms
(C) Mixtures
(D) Solutions
Answer: (B) Atoms
19. What is a compound?
(A) A mixture of substances in any proportion
(B) A substance formed when different elements combine chemically in fixed ratios
(C) A substance whose components retain their properties
(D) A substance that can always be separated by filtration
Answer: (B) A substance formed when different elements combine chemically in fixed ratios
20. What is the ratio of hydrogen atoms to oxygen atoms in water?
(A) 1:1
(B) 1:2
(C) 2:1
(D) 3:1
Answer: (C) 2:1
21. Why cannot hydrogen and oxygen in water generally be separated by physical methods?
(A) They are mixed without any interaction
(B) They are chemically combined in a fixed ratio
(C) They have different colours
(D) They are both gases
Answer: (B) They are chemically combined in a fixed ratio
22. What happens when sugar is heated strongly?
(A) It remains unchanged
(B) It decomposes into carbon and water
(C) It changes only into oxygen
(D) It becomes a mixture of iron and sulfur
Answer: (B) It decomposes into carbon and water
23. When iron filings and sulfur powder are simply mixed, the resulting sample is:
(A) A compound
(B) A mixture
(C) An element
(D) A pure substance
Answer: (B) A mixture
24. What is formed when a mixture of iron and sulfur is heated?
(A) Iron oxide
(B) Iron sulfide
(C) Sulfur dioxide
(D) Hydrogen sulfide
Answer: (B) Iron sulfide
25. Which observation helps distinguish iron sulfide from a mixture of iron and sulfur?
(A) Iron sulfide is attracted strongly by a magnet
(B) Iron sulfide has the same properties as iron and sulfur
(C) Iron sulfide is not attracted by a magnet and has properties different from its constituent elements
(D) Iron sulfide can be separated into iron and sulfur using a magnet
Answer: (C) Iron sulfide is not attracted by a magnet and has properties different from its constituent elements
NCERT Class 8 Science MCQ | Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures
Assertion–Reason Questions
Directions: Choose the correct option:
(A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
(B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(C) Assertion is true, but Reason is false.
(D) Assertion is false, but Reason is true.
1. Assertion: Air is a mixture.
Reason: Air contains several gases that are mixed together without undergoing chemical combination.
Answer: (A)
2. Assertion: Sugar dissolved in water is a uniform mixture.
Reason: The sugar particles are evenly distributed in water and cannot be distinguished separately.
Answer: (A)
3. Assertion: Water is a compound.
Reason: Hydrogen and oxygen are chemically combined in water in a fixed ratio of 2:1.
Answer: (A)
4. Assertion: A mixture of iron filings and sulfur can be separated using a magnet.
Reason: Iron retains its magnetic property when it is mixed with sulfur without chemical reaction.
Answer: (A)
5. Assertion: Iron sulfide has properties different from those of iron and sulfur.
Reason: Heating iron and sulfur causes them to chemically combine and form a new compound, iron sulfide.
Answer: (A)
