Gas Pressure
Pressure comes from particle collisions with container walls.
About this topic
Gas pressure is the force per unit area exerted by gas particles colliding with surfaces. Units include pascals (Pa), kilopascals, atmospheres (atm), millimetres of mercury (mmHg) and torr. Standard atmospheric pressure is 101.3 kPa = 1 atm = 760 mmHg.
Pressure rises if there are more particles, a higher temperature or a smaller volume. A barometer measures atmospheric pressure using a column of mercury; Torricelli found that air supports a column about 760 mm high. A manometer compares a gas sample with the atmosphere. Pressure decreases with altitude because there is less air above you, which is why ears pop in planes and water boils at lower temperatures on mountains.
Example: a car tyre gauge reads 220 kPa above atmospheric pressure, so the absolute pressure is about 321 kPa. A vacuum cleaner and a drinking straw work by lowering the pressure inside so that the higher atmospheric pressure pushes material in. To convert, use factors: 1 atm over 101.3 kPa, for instance.
Misconceptions: that suction pulls, when in reality the outside pressure pushes, and that gas pressure is caused by particles pushing each other. Also, gauge pressure differs from absolute pressure, and gas law calculations need absolute pressure.
Key ideas
- Units: Pa, atm, mmHg
- Barometers measure atmospheric pressure
- 1 atm = 101.3 kPa
Quick check
Use cases: where Gas Pressure helps
- Homework: review the key idea behind Gas Pressure before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Gas Pressure without notes.
- Visual learning: play with the interactive lab to see how Gas Pressure changes when you adjust its inputs.
- Teaching a friend: explain Gas Pressure in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Gas Pressure?
Pressure comes from particle collisions with container walls.
What will I learn in Gas Pressure?
Units: Pa, atm, mmHg. Barometers measure atmospheric pressure. 1 atm = 101.3 kPa.
Is Gas Pressure part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Gas Pressure lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Gas Pressure?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.