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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 an exothermic reaction?

Please select an answer first.

Correct answer: A

The correct answer is A reaction that releases energy to the surroundings.

  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.

Exothermic reactions transfer energy outward, often warming the surroundings.

2. QuestionMultiple choice

What is an endothermic reaction?

Please select an answer first.

Correct answer: B

The correct answer is A reaction that absorbs energy from the surroundings.

  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.

Endothermic reactions take in energy, often making the surroundings cooler.

3. QuestionMultiple choice

Which observation could support an exothermic reaction?

Please select an answer first.

Correct answer: C

The correct answer is The temperature of the surrounding solution increases without external heating..

  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 temperature increase indicates that energy may have been released to the surroundings.

4. QuestionMultiple choice

What does a catalyst do?

Please select an answer first.

Correct answer: D

The correct answer is It speeds up a reaction by lowering the activation energy without being used up overall..

  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.

Catalysts provide an alternative pathway with lower activation energy and are regenerated in the process.

5. QuestionMultiple choice

What is activation energy?

Please select an answer first.

Correct answer: A

The correct answer is The minimum energy needed for particles to begin 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.

Particles need enough energy for effective collisions and bond rearrangement to begin.

6. QuestionMultiple choice

Why can increasing temperature speed up many reactions?

Please select an answer first.

Correct answer: B

The correct answer is Particles move faster and collide more often with enough energy to react..

  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.

Higher temperature generally increases particle motion and the number of effective collisions.

7. QuestionMultiple choice

Which observation is most directly related to an energy change?

Please select an answer first.

Correct answer: C

The correct answer is A solution becomes noticeably warmer or cooler during the 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.

A temperature change provides observable evidence that energy was transferred during the reaction.

8. QuestionMultiple choice

Why does photosynthesis require energy input?

Please select an answer first.

Correct answer: D

The correct answer is Plants use light energy to build glucose from carbon dioxide and water..

  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.

Photosynthesis stores light energy in chemical bonds as glucose is formed.

9. QuestionMultiple choice

Why is burning fuel usually classified as exothermic?

Please select an answer first.

Correct answer: A

The correct answer is Combustion releases energy as heat and often light..

  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.

Fuel combustion forms new substances and releases energy to the surroundings.

10. QuestionMultiple choice

Which example is a physical change rather than an energy-releasing chemical reaction?

Please select an answer first.

Correct answer: B

The correct answer is Sugar dissolves in water without forming 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.

Dissolving can change how particles are distributed without creating a new substance.

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