Pressure & Volume Flashcards

All 6 cards in this deck

What equation links the pressure and volume of a fixed mass of gas held at a constant temperature?

$pV = \text{constant}$, with pressure $p$ in pascals (Pa).

What are the steps to find the new pressure of a fixed mass of gas at constant temperature when its volume changes?

e.g. $100\,000$ Pa of gas in $0.030$ m$^3$ is compressed to $0.025$ m$^3$

1. Find the constant: $100\,000 \times 0.030 = 3000$
2. Substitute the new volume: $p \times 0.025 = 3000$
3. Rearrange: $p = 3000 \div 0.025 = 120\,000$ Pa

Increasing the volume of a fixed mass of gas at constant temperature decreases its pressure. What happens to the collisions to explain this?

1. Collisions with the walls become less frequent (more time between collisions)
2. So the average force on the walls is lower
3. Pressure is the total force per unit area, so pressure falls

True or false? For a fixed mass of gas at constant temperature, doubling the volume doubles the pressure.

False. The pressure halves — pressure and volume are inversely proportional ($pV = \text{constant}$).

What shape is the graph of pressure against volume for a fixed mass of gas at constant temperature?

A curve falling from left to right (inverse proportion); a graph of $p$ against $\frac{1}{V}$ is a straight line through the origin.

In an investigation of how the pressure of the air in a syringe varies with its volume, what are the independent, dependent and control variables?

Independent: volume of the gas. Dependent: pressure of the gas. Control: temperature of the gas and mass of gas.