These are three questions and three answers.
Question 1. 1. Increasing the pressure on a gas __________ the volume the gas occupies.
Answer: decreases
Explanation:
The higher the pressure the more the gas is compressed, this is the less the volume it occupies.
You can observe this behavior of the gases in many daily facts: press the plunger of a syringe while you cover the exit hole; you can notice that the higher the pressure the lower the volume of the air trapped inside the syringe.
You can also show that from the Boyle's law for ideal gases: PV = constant, so P is inversely related to the volume.
Question 2. If the temperature of a gas increases, the volume of that gas __________
Answer: increases
Justification:
Use Charles' law for ideal gases: V/T = constant => T = constant x V => direct relation: the higher the temperature the greater the volume.
Question 3.. When the air in a submarine's huge air tanks is decompressed, what does the submarine do?
Answer: It floats.
Explanation:
Since the volume of the tanks and the submarine are not changing (remains constant) and the mass of the object (submarine with tanks) is decreasing (in virtue of the release of huge amount of air) the average density will decrease, which will make the submarine float.
Density = mass / volume, so if mass is decreased and volume kept, the densidy decreases.
