Reaction Models, Mass, and System Boundaries Worksheet
📝 Worksheet hard ⏱️ 22 minutes 8 problems
Reaction Models, Mass, and System Boundaries Worksheet
Grade 7 Science LearnCrux.com
Name:
Date:
Directions
- Fill in each blank carefully.
- Circle or mark the best answer for each multiple-choice question.
- Match each prompt to the best option before writing your answer.
- Use the larger space to show your thinking on word problems.
1. In a closed system, total __ stays the same during a chemical reaction.
2. Which setup best helps test conservation of mass?
3. Match the model clue to the best idea: same atoms before and after, different groupings
Match with:
Answer:
4. The starting substances in a reaction are called __.
5. Why can mass seem to decrease in an open reaction even when conservation still holds?
6. Which observation is strongest evidence that new substances formed?
7. Match the term to its role: product
Match with:
Answer:
8. Why should students use both particle models and measurements when explaining reactions?
📋 Teacher Answer Key
1. mass
2. a sealed container where gas cannot escape
3. particles rearranged during a reaction
4. reactants
5. Some matter can leave the measured system as gas, so the scale no longer includes all of the reaction products
6. gas forms, heat changes, and a new solid appears
7. new substance formed after the reaction
8. Models show how matter rearranges, and measurements provide evidence that the total mass of a closed system is conserved