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

2. 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

Which equation is balanced for the formation of water from hydrogen and oxygen?

Please select an answer first.

Correct answer: A

The correct answer is 2H2 + O2 -> 2H2O.

  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 four hydrogen atoms and two oxygen atoms on both sides.

2. QuestionMultiple choice

How many oxygen atoms are on the reactant side of 2H2 + O2 -> 2H2O?

Please select an answer first.

Correct answer: B

The correct answer is 2.

  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 formula O2 contains two oxygen atoms, and its coefficient is one.

3. QuestionMultiple choice

Why must a chemical equation be balanced?

Please select an answer first.

Correct answer: C

The correct answer is Atoms are conserved, so each element must have the same total count on both sides..

  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.

Balancing represents conservation of atoms during the reaction.

4. QuestionMultiple choice

Where are the products written in a standard chemical equation?

Please select an answer first.

Correct answer: D

The correct answer is To the right of the arrow.

  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.

Reactants are written on the left and products on the right of the arrow.

5. QuestionMultiple choice

What happens when a coefficient is placed before H2O?

Please select an answer first.

Correct answer: A

The correct answer is It changes the number of water molecules and multiplies both hydrogen and oxygen atoms..

  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 coefficient multiplies the entire formula without changing the identity of the substance.

6. QuestionMultiple choice

Why should a subscript not be changed when balancing an equation?

Please select an answer first.

Correct answer: B

The correct answer is Changing a subscript changes the identity and composition of the 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.

Subscripts define the formula, so changing one creates a different substance rather than balancing the original reaction.

7. QuestionMultiple choice

If 10 grams of reactants react in a closed system, what mass of products should form?

Please select an answer first.

Correct answer: C

The correct answer is 10 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.

In a closed system, conservation of mass means total product mass equals total reactant mass.

8. QuestionMultiple choice

Why is a closed system useful when measuring mass during a reaction?

Please select an answer first.

Correct answer: D

The correct answer is It prevents matter from entering or leaving while the reaction occurs..

  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 closed system allows the measured mass to represent all matter involved in the reaction.

9. QuestionMultiple choice

Which equation is balanced for nitrogen reacting with hydrogen to form ammonia?

Please select an answer first.

Correct answer: A

The correct answer is N2 + 3H2 -> 2NH3.

  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 nitrogen atoms and six hydrogen atoms on each side.

10. QuestionMultiple choice

What does it mean to say that atoms are rearranged in a reaction?

Please select an answer first.

Correct answer: B

The correct answer is The same atoms form new connections or combinations in the products..

  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 atoms remain present but their arrangement and bonding change to form products.

Previous testNext test