What is 0 °C in kelvin?

273 K. Add 273 to the Celsius temperature.

The volume of a fixed mass of gas is halved at constant temperature. What happens to the pressure?

It doubles. Pressure × volume stays constant.

What is absolute zero?

−273 °C. It is the lowest possible temperature, 0 K.

A sealed can of gas is heated. Why does the pressure rise?

The particles hit the walls harder and more often. Faster particles collide with more force and more frequently.

A gas at 200 kPa has a volume of 3 m³. At the same temperature its volume becomes 6 m³. What is the pressure?

100 kPa. 200 × 3 = p × 6, so p = 100 kPa.

Gases, pressure and temperature · Edexcel IGCSE Physics

In plain words

Trap some gas and you can change three things: its pressure, its volume and its temperature. Squash it into a smaller volume and the pressure goes up. Heat it in a fixed container and the pressure goes up. At a steady temperature, pressure × volume stays the same.

Three things to know

Heating a gas in a fixed volume increases its pressure: the particles move faster and hit the walls harder and more often.
At constant temperature, pressure × volume is constant for a fixed mass of gas (p₁V₁ = p₂V₂). Halve the volume and the pressure doubles.
Kelvin temperature = Celsius temperature + 273. Absolute zero (0 K, −273 °C) is where particles have their least possible energy.

Worked example

A gas has a volume of 60 cm³ at a pressure of 100 kPa. It is squashed to 20 cm³ at the same temperature. Find the new pressure.

p₁V₁ = p₂V₂, so 100 × 60 = p₂ × 20.
p₂ = 6000 ÷ 20.
= 300 kPa.

Tips and tricks

Sense-check: a smaller volume must give a bigger pressure. If your answer went the other way, you divided by the wrong number.
To change °C into kelvin, add 273.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Gases, pressure and temperature: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

What is 0 °C in kelvin?
- 0 K
- 100 K
- 273 K (the answer)
- 373 K
Add 273 to the Celsius temperature.
The volume of a fixed mass of gas is halved at constant temperature. What happens to the pressure?
- It halves.
- It stays the same.
- It doubles. (the answer)
- It becomes four times as great.
Pressure × volume stays constant.
What is absolute zero?
- 0 °C
- the freezing point of water
- −273 °C (the answer)
- 273 °C
It is the lowest possible temperature, 0 K.
A sealed can of gas is heated. Why does the pressure rise?
- The particles expand.
- The particles hit the walls harder and more often. (the answer)
- More particles are made.
- The can gets smaller.
Faster particles collide with more force and more frequently.
A gas at 200 kPa has a volume of 3 m³. At the same temperature its volume becomes 6 m³. What is the pressure?
- 50 kPa
- 100 kPa (the answer)
- 400 kPa
- 1200 kPa
200 × 3 = p × 6, so p = 100 kPa.
What is 400 K in degrees Celsius?
- 673 °C
- 400 °C
- 273 °C
- 127 °C (the answer)
Subtract 273.

6 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

4 questions, 10 marks. Write your answers on paper, then check them.

Gases, pressure and temperature

Edexcel International GCSE Physics 4PH1 · 10 marks · papermunch.org

Name ______________________________ Date ______________

Convert 27 °C to kelvin.[1]
Show answerHide answer
300 K. 27 + 273.
I got this one
A gas has a volume of 600 cm³ at a pressure of 100 kPa. It is compressed at constant temperature to 200 cm³. Calculate the new pressure.[3]
Show answerHide answer
300 kPa. 100 × 600 = p × 200.
I got this one
Explain, using ideas about particles, why the pressure in a car tyre rises on a hot day.[3]
Show answerHide answer
The air particles move faster, so they hit the tyre walls harder and more often.
I got this one
A gas at 150 kPa occupies 4.0 m³. It expands at constant temperature until its pressure is 50 kPa. Calculate its new volume.[3]
Show answerHide answer
12 m³. 150 × 4.0 = 50 × V.
I got this one

Answers: Gases, pressure and temperature

1. 300 K. 27 + 273.
2. 300 kPa. 100 × 600 = p × 200.
3. The air particles move faster, so they hit the tyre walls harder and more often.
4. 12 m³. 150 × 4.0 = 50 × V.