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Chemical Reactions Practice Tests

These Grade 8 Science practice tests cover chemical and physical changes, reactants, products, evidence of reactions, conservation of mass, balanced equations, coefficients, subscripts, energy changes, catalysts, and reaction types.

Skills covered

  • Distinguishing chemical reactions from physical changes
  • Identifying reactants, products, coefficients, subscripts, and balanced equations
  • Applying conservation of atoms and mass in closed systems
  • Analyzing exothermic and endothermic energy changes and catalysts
  • Recognizing synthesis, decomposition, combustion, replacement, and neutralization patterns

How to use these practice tests

Look for evidence of new substances, identify the starting and ending materials, and count atoms on both sides of an equation. Use coefficients to balance equations without changing subscripts or substance identities.

For more Grade 8 Science practice, return to the Grade 8 Science category.

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Grade 8 Chemical Reactions Practice Tests

Practice Grade 8 Science questions about chemical changes, reactants, products, conservation of mass, balanced equations, energy, catalysts, and reaction types.

Choose the best answer for each question. Use observations, atom counts, balanced equations, energy evidence, and reaction patterns to analyze chemical reactions.

10 Questions
0/10 Questions0 %
Correct 0
Incorrect 0
Unanswered 10
1. QuestionMultiple choice

What is a synthesis reaction?

Please select an answer first.

Correct answer: A

The correct answer is A reaction in which two or more substances combine to form one product..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

Synthesis combines simpler substances into a more complex product.

2. QuestionMultiple choice

What is a decomposition reaction?

Please select an answer first.

Correct answer: B

The correct answer is A reaction in which one compound breaks into simpler substances..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

Decomposition separates one compound into two or more simpler products.

3. QuestionMultiple choice

What pattern describes a single-replacement reaction?

Please select an answer first.

Correct answer: C

The correct answer is One element replaces another element in a compound..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

In single replacement, a free element takes the place of a similar element in a compound.

4. QuestionMultiple choice

What is combustion?

Please select an answer first.

Correct answer: D

The correct answer is A reaction in which a substance reacts rapidly with oxygen and releases energy..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

Combustion commonly produces heat and light as a substance reacts with oxygen.

5. QuestionMultiple choice

What is a precipitate?

Please select an answer first.

Correct answer: A

The correct answer is A solid that forms from solutions during a reaction.

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

An unexpected solid forming in a mixture can be evidence of a chemical reaction.

6. QuestionMultiple choice

What may gas bubbles indicate when two solutions are mixed?

Please select an answer first.

Correct answer: B

The correct answer is A new gas may have formed during a chemical reaction..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

Unexpected gas formation is one possible sign that new substances formed.

7. QuestionMultiple choice

Why can an unexpected color change be evidence of a chemical reaction?

Please select an answer first.

Correct answer: C

The correct answer is It may indicate that a substance with different properties formed..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

A new color can signal new substances, though the observation should be considered with other evidence.

8. QuestionMultiple choice

Why is a new odor not always enough to prove a chemical reaction?

Please select an answer first.

Correct answer: D

The correct answer is Odor can come from contamination, mixing, or physical release rather than a new substance..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

A single observation can have multiple explanations, so additional evidence and safe procedures are needed.

9. QuestionMultiple choice

What commonly happens in an acid-base neutralization?

Please select an answer first.

Correct answer: A

The correct answer is An acid and a base react to form water and a salt..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

Neutralization reduces acidic and basic properties and commonly produces water and an ionic salt.

10. QuestionMultiple choice

Which observation best supports that a new solid formed in a reaction?

Please select an answer first.

Correct answer: B

The correct answer is A cloudy mixture produces particles that settle to the bottom..

  1. Identify the reaction information: Determine whether the question describes a chemical change, reactant, product, equation, energy change, or reaction pattern.
  2. Track atoms and energy: Count each type of atom, distinguish coefficients from subscripts, and compare energy before and after the reaction.
  3. Check the evidence: Use observations such as gas, precipitate, temperature, color, or new odor together with conservation and balanced equations.

Settling particles in a previously clear mixture are evidence of a precipitate.

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