Gases and Pressure Lecture 1 Notes

Flashcards for key concepts relating to gases and pressure from the lecture.

Gas

A state of matter with no fixed shape or volume.

Pressure

Force per unit area.

Atmospheric pressure

Pressure caused by gases in the atmosphere.

atm

Atmosphere; a unit of pressure.

torr

A unit of pressure equal to mmHg.

mmHg

Millimeters of mercury; pressure based on mercury column height.

psi

Pounds per square inch.

kPa

Kilopascals; SI-related pressure unit.

Barometer

Tool used to measure atmospheric pressure.

Manometer

Tool used to measure gas pressure.

Vacuum

A space with no gas particles, or almost none.

Why do gases create pressure?

Due to gas particles constantly moving and colliding with surfaces.

Why does the paint can collapse when gas is removed from the inside?

Because of a pressure difference between the outside and inside.

Why does pressure decrease at higher altitude?

Because there are fewer gas particles pushing down as altitude increases.

Define pressure.

Pressure is force per unit area.

Define atmospheric pressure.

The pressure caused by gases in Earth’s atmosphere colliding with surfaces.

Define barometer.

A device used to measure atmospheric pressure.

Define manometer.

A device used to measure gas pressure.

Convert atm to torr.

1 atm = 760 torr.

Convert mmHg to atm.

1 mmHg = 0.001316 atm.

Convert atm to kPa.

1 atm = 101.3 kPa.

Closed-end manometer

A U-shaped tube with one side containing gas and the other side in vacuum.

Open-end manometer

A device with one side open to the atmosphere, comparing gas pressure to atmospheric pressure.

P_{gas} = P_{atm} -
abla h

Used when atmospheric pressure is greater than gas pressure.

P_{gas} = P_{atm} +
abla h

Used when gas pressure is greater than atmospheric pressure.