Squeezing matter
Pressure changes gases the most.
A bicycle pump
You push the handle of a pump with a finger on its outlet. The air inside gets squeezed.
What happens to the air inside?
What this lesson covers
The idea
Increasing pressure pushes gas particles closer, decreasing volume and increasing density; liquids, being nearly incompressible, change only slightly, and the density change in solids is usually negligible.
A bicycle pump
You push the handle of a pump with a finger on its outlet. The air inside gets squeezed.
What happens to the air inside?
- It takes less volume, so it is denser
- It takes more volume
- Nothing happens
Press on each state
Open each tab.
Pressure and density
For gases, increasing pressure moves particles closer, so the volume decreases and the density increases. Liquids are nearly incompressible. Solids are even less affected.
Gases: more pressure → less volume, more density. Liquids: small change. Solids: change usually negligible.
- State | Effect of pressure on density
- Gas | Density increases
- Liquid | Changes slightly
- Solid | Usually negligible
Notes
Pressure raises the density of gases a lot; liquids slightly; solids hardly at all.
Check yourself
Increasing the pressure on a gas makes its density …
The density of which state is most affected by pressure?
Liquids are almost …
The change in the density of solids under pressure is usually …
- increase — correct. Yes!
- decrease. The particles are pushed closer, so the density increases.
- stay the same. The density increases.
- Solid. Solids are the least affected.
- Gas — correct. Yes!
- Liquid. Liquids are only slightly affected.
- weightless. Liquids are nearly incompressible.
- gases. Liquids are nearly incompressible.
- incompressible — correct. Yes!
- negligible — correct. Yes!
- very large. It is usually negligible.
- equal to a gas. Solids are even less affected than liquids.