Unit 1 Worksheet 1: Mass and Change
1. When you pulled the steel wool apart, you found that the mass was unchanged. But, when you heated the steel wool, you found that the mass changed. Explain.
Pulling the steel wool apart only changed the shape so all of the particles were still there. Heating the steel wool caused it to combine with something (O2) in the air.
Draw diagrams (at the simple particle level) of the steel wool before and after the change.
Steel wool-pulled apart Steel wool-heated before after before after
2. When ice melts, the volume of water is smaller than that of the ice. How does the mass of the water compare to the mass of the ice?
It changed because when the added particles from the alka-seltzer reacted with the water, it caused particles to leave.
Draw diagrams (at the simple particle level) of the ice and water. Use small circles to represent the particles of water
3. When the sugar dissolved in the water, you found that the mass remained unchanged. When the Alka-Seltzer dissolved in the water, the mass of the system changed. Explain.
Alka- Seltzer was an open system and matter left the system. Sugar was a closed system.
Draw diagrams (at the simple particle level) of each of the materials before and after it was dissolved.
4. State the Law of Conservation of Mass in your own words.
If nothing leaves or enters the system, then there is no change in mass.
