Question

A sample of gas in a sealed container (fixed volume) is heated from room temperature to 80.0°C.

Answer 1

Hello!

A) When the temperature inside the container increases, the pressure inside the container increases as well. 

An example for that is when you have an aerosol can and start heating it. The pressure of the gas inside the aerosol can will start to increase, and that would lead to the exploding of the can if heating is kept for too long. Bombs work on this principle too: The heat from the violent chemical reaction inside the closed compartment increase the pressure of the gases until the fragments are ejected at high velocities. 

B) The effect of temperature on the pressure of a gas illustrates Gay-Lussac's Law.

This law was formulated by the famous French chemist that gives it its name. It relates the expansion of a gas with the increase in temperature when the volume is left constant. The Gay-Lussac's Law can be expressed as follows, for the case of this exercise:

$\frac{P1}{T1}= \frac{P2}{T2} \\ \\ P2= \frac{P1}{T1}*T2=P1* \frac{80 degC}{25degC}= P1*3,2$

You can see that the factor that is multiplying P1 is higher than 1 for the case of heating from 25 °C to 80 °C, so the pressure will increase.

C) At a molecular level, when the temperature is raised the kinetic energy of the molecules inside the container will increase. This increase in the kinetic energy will cause the molecules to move faster, and to hit the walls of the container more often. This causes an increase in the pressure inside the container because there more hits means more force on the walls of the container, and that is the definition of pressure. 

Have a nice day!