MCQs
1. A pure substance is defined as a substance that:
A) Contains only one phase
B) Has uniform and fixed composition
C) Can be separated by filtration
D) Contains multiple elements only
2. Which of the following is NOT a pure substance?
A) Oxygen
B) Gold
C) Air
D) Water
3. Which property is characteristic of a pure substance?
A) Variable boiling point
B) Fixed melting point
C) Easily separable by physical means
D) Non-uniform composition
4. Which of the following is an element?
A) Carbon dioxide
B) Sodium chloride
C) Copper
D) Water
5. Which of the following is a compound?
A) Iron
B) Oxygen
C) Sodium chloride
D) Helium
6. Diamond is considered a pure substance because:
A) It is shiny
B) It is made of carbon atoms only
C) It contains impurities
D) It is rare
7. Which of the following statements is TRUE about compounds?
A) They can be separated by physical methods
B) They have variable composition
C) Elements are chemically combined in fixed ratio
D) They contain only one type of atom
8. Which of the following has a fixed composition but can be broken chemically?
A) Element
B) Compound
C) Mixture
D) Solution
9. Which method can be used to separate a compound into its elements?
A) Filtration
B) Distillation
C) Chemical reaction
D) Evaporation
10. Which of the following is a pure substance but NOT an element?
A) Oxygen
B) Nitrogen
C) Water
D) Iron