Introduction to Chemistry Quiz

Grade 6 · Science · Quiz

Test your knowledge of atoms, elements, compounds, mixtures, and physical versus chemical changes.

Questions

1. What does the atomic number of an element represent?

   1. Number of neutrons
   2. Number of electrons only
   3. Number of protons
   4. Total number of particles in the nucleus
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   Answer: Number of protons

   The atomic number equals the number of protons in an atom's nucleus. It uniquely identifies each element — no two elements have the same atomic number.

2. Water (H2O) is best described as a:

   1. Mixture
   2. Element
   3. Compound
   4. Solution
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   Answer: Compound

   Water (H2O) is a compound because it is made of two different elements (hydrogen and oxygen) that are chemically bonded together in a fixed 2:1 ratio.

3. Which of the following is a physical change?

   1. A candle burning
   2. Bread baking in an oven
   3. A log decomposing in a forest
   4. Glass being shattered
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   Answer: Glass being shattered

   Shattering glass is a physical change — the glass changes shape but its chemical composition (silicon dioxide) remains the same. Burning, baking, and decomposing are all chemical changes.

4. What are the three subatomic particles that make up an atom?

   1. Protons, neurons, and isotopes
   2. Protons, neutrons, and electrons
   3. Nucleons, electrons, and ions
   4. Atoms, molecules, and compounds
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   Answer: Protons, neutrons, and electrons

   Atoms are made of three types of subatomic particles: protons (positive charge, in nucleus), neutrons (no charge, in nucleus), and electrons (negative charge, orbit nucleus).

5. Saltwater is an example of a:

   1. Compound
   2. Pure element
   3. Mixture
   4. New chemical substance
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   Answer: Mixture

   Saltwater is a mixture because salt and water are not chemically bonded together. They retain their own properties and can be separated by evaporation — a physical process.

6. Which observation is the BEST evidence of a chemical change?

   1. Ice melting in a glass of water
   2. A gas is produced when vinegar and baking soda are combined
   3. Sand being filtered out of water
   4. A balloon being stretched
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   Answer: A gas is produced when vinegar and baking soda are combined

   Production of a gas (bubbling/fizzing) is classic evidence of a chemical change, indicating a new substance has formed. Vinegar and baking soda react to produce carbon dioxide gas.

7. Elements in the same group (column) on the Periodic Table have similar chemical properties.

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   Answer: True

   Elements in the same group (vertical column) on the Periodic Table have the same number of valence electrons, giving them similar chemical properties and reactivity patterns.

8. The type of change that produces new substances with different chemical properties is called a ________ change.

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   Answer: chemical

   A chemical change (or chemical reaction) produces one or more new substances with different properties. Unlike physical changes, chemical changes are often difficult or impossible to reverse.

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