Atoms and Molecules Quiz - CBSE Class 9 Science

Free practice quiz: Atoms and Molecules (CBSE Class 9 Science). 18 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. What is the smallest particle of an element that retains its chemical properties?

   1. Atom
   2. Molecule
   3. Compound
   4. Ion
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   Answer: A. Atom

   An atom is the smallest particle of an element that retains the element's chemical properties.

2. Which of the following correctly represents the atomic composition of carbon dioxide?

   1. CO2
   2. C2O
   3. CO
   4. OC
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   Answer: A. CO2

   Carbon dioxide is composed of one carbon atom and two oxygen atoms, which is represented by the chemical formula CO2.

3. Which is a characteristic of chemical compounds?

   1. Fixed ratio of atoms
   2. Variable ratio of elements
   3. Only one type of atom
   4. Can be separated by physical means
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   Answer: A. Fixed ratio of atoms

   Chemical compounds have a fixed ratio of atoms of different elements, which define the compound's chemical formula.

4. Which term describes a molecule consisting of two atoms?

   1. Diatomic
   2. Monatomic
   3. Polyatomic
   4. Triatomic
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   Answer: A. Diatomic

   Diatomic refers to a molecule composed of two atoms, such as O2 or H2.

5. Which is the heaviest component of an atom in terms of mass?

   1. Neutron
   2. Proton
   3. Electron
   4. Quark
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   Answer: A. Neutron

   The neutron is slightly more massive than a proton and vastly more massive than an electron. Quarks are components of protons and neutrons.

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