Chemistry – Multiple Choice Questions (MCQs)

1. 1. What is the basic unit of matter?

   • A. Atom
   • B. Molecule
   • C. Element
   • D. Compound

2. 2. What is an element?

   • A. A substance made up of two or more different types of atoms chemically combined
   • B. A substance that cannot be broken down into simpler substances by chemical means
   • C. A mixture of different substances
   • D. A substance that is always a gas at room temperature

3. 3. What is a compound?

   • A. A substance made up of only one type of atom
   • B. A substance that can be easily separated by physical means
   • C. A substance made up of two or more different types of atoms chemically combined in a fixed ratio
   • D. A substance that is always a liquid

4. 4. What is a mixture?

   • A. A substance made up of two or more substances chemically combined
   • B. A substance with a fixed ratio of components
   • C. A substance where components are not chemically bonded and can be separated by physical means
   • D. A pure substance

5. 5. What is a chemical change?

   • A. A change in the physical form of a substance
   • B. A change that results in the formation of a new substance with different properties
   • C. Melting of ice
   • D. Boiling of water

6. 6. What is an atomic number?

   • A. The number of neutrons in an atom
   • B. The number of protons in an atom
   • C. The number of electrons in an atom
   • D. The sum of protons and neutrons

7. 7. What is mass number?

   • A. The number of protons in an atom
   • B. The number of neutrons in an atom
   • C. The number of electrons in an atom
   • D. The sum of protons and neutrons in an atom

8. 8. What are isotopes?

   • A. Atoms of the same element with the same number of protons but different numbers of neutrons
   • B. Atoms of different elements with the same number of protons
   • C. Atoms with the same mass number but different atomic numbers
   • D. Molecules with the same chemical formula but different structures

9. 9. What is a molecule?

   • A. The smallest particle of an element
   • B. The smallest particle of a compound that retains the chemical properties of that compound
   • C. A charged atom
   • D. A mixture of atoms

10. 10. What is an ion?

    • A. A neutral atom
    • B. An atom or molecule that has gained or lost one or more electrons
    • C. A molecule with no charge
    • D. A radioactive atom

11. 11. What are cations?

    • A. Positively charged ions
    • B. Negatively charged ions
    • C. Neutral atoms
    • D. Molecules with no charge

12. 12. What are anions?

    • A. Positively charged ions
    • B. Negatively charged ions
    • C. Neutral molecules
    • D. Radioactive isotopes