Atom, Molecules and Compound

1. What is an atom?

a. The smallest unit of matter
b. A big stone
c. A type of gas

2. Molecule is formed by the combination of:

a. Two or more atoms
b. Only metals
c. Only water

3. Which of these is a molecule?

a. H₂O
b. Iron nail
c. Plastic bag

4. A compound is made up of:

a. Same atoms only
b. Different atoms chemically combined
c. Only gases

5. Water (H₂O) is a:

a. Element
b. Metal
c. Compound

6. Which one is an atom?

a. O
b. CO₂
c. H₂O

7. Which of the following is an element?

a. Oxygen
b. Salt
c. Sugar

8. The smallest particle of an element is called:

a. Compound
b. Atom
c. Molecule

9. CO₂ represents a:

a. Metal
b. Molecule
c. Liquid

10. Which one is a compound?

a. Gold
b. Oxygen gas
c. Carbon dioxide

11. One molecule of water has:

a. 1 Hydrogen + 2 Oxygen
b. 2 Hydrogen + 1 Oxygen
c. 3 Oxygen

12. Salt (NaCl) is a:

a. Compound
b. Element
c. Gas

13. Molecules of elements contain:

a. Same type of atoms
b. Different atoms
c. Only liquids

14. Which of these is NOT an element?

a. Carbon
b. Nitrogen
c. Sugar

15. Which one is an example of a compound?

a. CO₂
b. O₂
c. N₂

16. Which statement is true?

a. Atoms are visible with naked eye
b. Atoms are extremely small
c. Atoms are large particles

17. Molecules of compounds contain:

a. Same atoms only
b. Different atoms
c. Only metals

18. Hydrogen is a/an:

a. Element
b. Compound
c. Mixture

19. A molecule of oxygen (O₂) contains:

a. 1 oxygen atom
b. 2 oxygen atoms
c. 3 oxygen atoms

20. Which one is a mixture?

a. Air
b. Water
c. Carbon dioxide

21. A chemical formula shows:

a. Size of molecules
b. Number and type of atoms
c. Color of substance

22. The formula of carbon dioxide is:

a. CO
b. CO₂
c. C₂O

23. Sodium chloride is formed by:

a. Sodium + Chlorine
b. Hydrogen + Oxygen
c. Carbon + Oxygen

24. Which one is an example of an element?

a. Iron
b. Salt
c. Water

25. Molecules can be:

a. Single atoms only
b. Two or more atoms joined
c. Only large objects

26. Which particle cannot be broken by chemical methods?

a. Compound
b. Molecule
c. Element

27. In a compound, atoms are:

a. Physically mixed
b. Chemically combined
c. Randomly scattered

28. Which is a compound used for breathing?

a. CO₂
b. O₂
c. H₂O

29. A molecule of methane (CH₄) contains:

a. 1 carbon & 4 hydrogen
b. 4 carbon & 1 hydrogen
c. 2 hydrogen only

30. Which is the smallest?

a. Molecule
b. Atom
c. Compound