NumicornNumicornLearn, solve, progress

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.

Select a test

5 Tests
1. Test2. Test3. Test4. Test5. Test

5. Test

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

Why should a student record temperature before and after a reaction?

Please select an answer first.

Correct answer: A

The correct answer is The comparison can show whether energy was transferred to or 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.

Before-and-after measurements provide evidence of an energy change.

2. QuestionMultiple choice

A reaction has 18 grams of reactants and occurs in a closed container. What total product mass is expected?

Please select an answer first.

Correct answer: B

The correct answer is 18 grams.

  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.

Conservation of mass means the total mass remains 18 grams in a closed system.

3. QuestionMultiple choice

Which equation is balanced?

Please select an answer first.

Correct answer: C

The correct answer is 2Mg + O2 -> 2MgO.

  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.

The balanced equation has two magnesium atoms and two oxygen atoms on each side.

4. QuestionMultiple choice

How does balancing an equation support the law of conservation of mass?

Please select an answer first.

Correct answer: D

The correct answer is It shows that each type of atom has the same total count before and after 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.

Balanced coefficients represent conservation of each element during the reaction.

5. QuestionMultiple choice

Why can a catalyst increase reaction rate without changing the total products?

Please select an answer first.

Correct answer: A

The correct answer is It changes the pathway and lowers activation energy but is not consumed 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.

A catalyst affects reaction speed while remaining available after the reaction.

6. QuestionMultiple choice

Which reaction type is represented by A + B -> AB?

Please select an answer first.

Correct answer: B

The correct answer is Synthesis.

  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.

Two reactants combine to make one product, which is the general synthesis pattern.

7. QuestionMultiple choice

A graph shows the temperature of a solution rising after reactants are mixed. What claim is best supported?

Please select an answer first.

Correct answer: C

The correct answer is The reaction likely released 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.

A temperature rise supports an exothermic energy transfer, but it does not by itself identify every reaction type.

8. QuestionMultiple choice

Which evidence would make a claim about a chemical reaction strongest?

Please select an answer first.

Correct answer: D

The correct answer is Several observations agree, such as gas formation, temperature change, and a balanced equation..

  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.

Multiple consistent observations and a balanced representation provide stronger support than appearance or opinion.

9. QuestionMultiple choice

Which statement correctly distinguishes a chemical and physical change?

Please select an answer first.

Correct answer: A

The correct answer is Chemical change forms new substances, while physical change changes form or state without forming new 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.

The key difference is whether new substances with new properties form.

10. QuestionMultiple choice

What is the best first step when analyzing an unfamiliar chemical equation?

Please select an answer first.

Correct answer: B

The correct answer is Identify the formulas, locate reactants and products, and count each type of atom..

  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.

Reading formulas and counting atoms provides the information needed to interpret and balance the equation.

Previous testNext test