初三课外练习化学选择题及答案20题
1. Which of the following elements is a noble gas?
  A) Oxygen
  B) Hydrogen
  C) Helium
  D) Carbon
Answer: C
2. The atomic number of an element determines its:
  A) Mass number
  B) Number of protons
  C) Number of electrons
  D) Number of neutrons
Answer: B
3. Chemical reactions involve the:
  A) Formation of new substances
  B) Separation of atoms
  C) Creation of energy
  D) Elimination of electrons
Answer: A
4. A substance that cannot be broken down into simpler substances by chemical means is called a/an:
  A) Element
  B) Compound
  C) Molecule
  D) Atom
Answer: A
5. The pH scale is used to measure the:
  A) Temperature of a substance
  B) Acidity or basicity of a solution
  C) Volume of a liquid
  D) Mass of an object
Answer: B
6. Which of the following is an example of a physical change?
  A) Burning wood
  B) Rusting of iron
  C) Boiling water
  D) Digesting food
Answer: C
7. The chemical symbol for gold is:
  A) Au
  B) Ag
  C) Fe
  D) Pb
Answer: A
8. Which of the following is a non-metal?
  A) Sodium
  B) Calcium
  C) Nitrogen
  D) Magnesium
Answer: C
9. The atomic mass of an element is determined by the sum of:
  A) Protons and neutrons
  B) Protons and electrons
  C) Electrons and neutrons
  D) Electrons, protons, and neutrons
Answer: A
10. Which of the following is an example of a physical property of matter?
    A) Flammability
    B) Reactivity
    C) Density
    D) Corrosiveness
Answer: C
11. Which of the following is NOT a state of matter?reaction mass
    A) Solid
    B) Liquid
    C) Gas
    D) Energy
Answer: D
12. The process of a liquid changing into a gas is called:
    A) Condensation
    B) Evaporation

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