Particle Model & Pressure Practice Questions

The laboratory is kept at a temperature of $21\ ^\circ\text{C}$.

Convert this temperature to kelvin.

Liquid nitrogen, used to cool the samples, boils at a temperature of $77\ \text{K}$.

Convert this temperature to degrees Celsius.

Sample X is stored at $150\ \text{K}$.

Sample Y is stored at $-140\ ^\circ\text{C}$.

Determine which sample is at the colder temperature. You must show your working.

Which of these is a correct statement about absolute zero?

Put a cross ( ☒ ) in the box next to your answer.

☐ A   It is the temperature, $0\ ^\circ\text{C}$, at which all gases turn into liquids.

☐ B   It is the lowest possible temperature, $-273\ ^\circ\text{C}$, at which the particles stop moving.

☐ C   It is the temperature, $-273\ \text{K}$, at which the particles of a gas move most quickly.

☐ D   It is the temperature, $273\ ^\circ\text{C}$, at which a gas has no particles left in it.

Explain, in terms of the particles, how the compressed air exerts a pressure on the inside walls of the cylinder.

Convert each of these two temperatures to the kelvin scale.

The reading on the pressure gauge increases as the air is heated.

Explain, in terms of the particles of the air, why the pressure increases.

Complete the table to show what happens to each quantity when the cylinder is placed in the freezer.

Write increases, decreases or stays the same in each empty box.

Quantity	What happens to it
the pressure of the gas inside the cylinder
the mean speed of the particles inside the cylinder
the mean distance between the particles inside the cylinder

Explain why the mean distance between the particles does not change.

The student says:

"The results show that the pressure is directly proportional to the temperature in degrees Celsius."

Use the data in the table to show that the student is wrong.

The student plots pressure against temperature in $^\circ\text{C}$ and obtains a straight line. When the line is extended backwards it crosses the temperature axis at $-273\ ^\circ\text{C}$.

Explain what this temperature is called and what it means in terms of the particles of the gas.

An aerosol can of spray paint carries this warning.

Pressurised container. Do not store above $50\ ^\circ\text{C}$. Do not pierce or burn, even when empty.

The can is sealed and its volume does not change.

Explain, using the particle model, why the pressure inside the can increases when it is stored in a hot place, and why this could make the can burst.