Science content:
 Gas is matter—it consists of particles and space.
 Gas compresses when force is applied; gas expands when force is withdrawn.
Conducting Investigations objective
 Use syringes to observe the effects of pressure on gases.
Building Explanations objective
 Use drawings and words to explain gas compression and expansion.
1.
ERROR: Drawings show different numbers of particles when gases are compressed or when they are expanded in closed syringes.
HINT: Once the syringe is shut, particles cannot leave or enter the syringe.
CORRECT: Once a syringe is closed, the number of particles inside will stay the same when it is compressed or expanded.
Study: p 1 pretest , p 26 and 27 lab manual, p 16 – 19 hardcover text
2.
ERROR: Students may say that particles of a gas are compressed or expanded. It is correct to say that the GAS is compressed or expanded. But the individual particles of a gas do not get smaller nor do they get larger.
CORRECT: Instead, the particles can be said to get closer together when pressed into a smaller space or spread out when given more space.
Study: p 2 of pretest, p 25, 29 lab manual, p 20-22 hardcover text
3.
ERROR: Students assume that the space between the particles of a gas is filled with more gas.
CORRECT: Each gas is made up of just two things: particles and space. The answer to the question "What is between the particles of a gas?" is "Nothing".
4.
ERROR: Students may use phases such as "The particles want to get out of the bottle." instead of simply describing the behavior of the gas particles.
Scientific explanations should not include magical images such as particles that have feelings.
CORRECT: Gas particles move very fast and bump into each other and the walls of the containers that hold them. They spread out evenly to fill the space.