Unit 2b Matter & Gas Laws

The illustrations below represent the expansion of a gas in a cylinder of an engine. The piston moves as the gas volume changes. What could have been done to the gas in the cylinder to bring about this change in volume?

• Half of the molecules were released.
• The temperature was doubled.
• The condensation rate for the gas was doubled.
• The amount of heat in the gas was reduced by one half.

Three identical balloons each contains the same amount of gas molecules. One balloon contains oxygen, one contains nitrogen, and one contains argon. Which of the following will happen if the balloons are placed in a warmer room?

• The balloon with argon will decrease most in volume because argon is a noble gas.
• All of the balloons will decrease in volume equally because the temperature increased.
• The balloon with oxygen will increase most in volume because oxygen has the largest molecules.
• all of the balloons will increase in volume equally because they have equal numbers of molecules

Assuming pressure is held constant, which of the following graphs shows how the volume of an ideal gas changes with temperature?

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Under what circumstance might a gas decrease in volume?

• The gas is held constant at STP.
• The gas remains under uniform temperature.
• The gas is placed under increasing pressure.
• The gas undergoes a decrease in pressure.

What is the melting point of the substance below and during what time frame does the substance have the lowest kinetic energy?

• 150 C, 0-2 min
• 150 C, 2-6 min
• 90 C, 10-12 min
• 90 C, 14-16 min

A student experiments with nitrogen gas, changing one variable at a time: temperature, pressure, or volume.Unfortunately, the student forgot to label the axes. Which of the following pairs of labels are possible for the graph shown above?

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Which of the following best explains why doubling the temperature of an ideal gas in a closed container doubles the pressure?

• Increasing the temperature increases the size of the gas molecules, which then can put more pressure on the vessel walls.
• Increasing the temperature decreases the volume, causing molecules to strike the vessel walls more frequently.
• Increasing the temperature causes gas molecules to collide more often and with enough force to displace electrons.
• Increasing the temperature causes gas molecules to move more rapidly, striking the vessel walls more frequently and with greater force.

Which is the best explanation for the small puddle around Cup A and the larger puddle around Cup B?

• Cup A contained more ice than Cup B.
• Cup A was a better insulator than Cup B slowing the tranfer of heat
• Cup A had a greater volume of lemonade than Cup B.
• The contents of Cup A were initially colder than the contents of Cup B.

When a scuba diver is deep underwater and exhales, air bubbles form and rise to the surface of the water. Which of the following statements best describes what happens to the air bubbles as they rise to the surface?

• The number of gas molecules in the bubbles increases, and the diameter (volume) of the bubbles increases
• The number of gas molecules in the bubbles decreases, and the diameter(volume) of the bubbles decreases.
• The number of gas molecules in the bubbles remains the same, and the diameter (volume) of the bubbles increases.
• The number of gas molecules in the bubbles remains the same, and the diameter(volume) of the bubbles decreases.

When a cup of hot chocolate cools from 90◦C to 80◦C, which of the following is happening to the molecules of the liquid?

• Their rate of motion is decreasing.
• Their valence electrons are being lost.
• Their positions are becoming fixed in crystals
• Their average distance from adjacent molecules in increasing.