Solids, Liquids, and Gases 

Density

It relates the mass of a substance to the amount of space it occupies.
- Density = Mass per unit volume of a material. 

- The average density of an object determines whether it floats or sinks. E.g., a solid will float on liquid if it has a lower density.
- Density doesn't vary with size or shape. 

Finding the Density of an Object

- If the shape is a box, measure its length, width, and height using a ruler. Then, multiply these measurements together to determine the volume.
- If the shape of the object is irregular, you can determine its volume by immersing it in a eureka can filled with water. Water displaced by the object is transferred to the measuring cylinder. As the object's volume is water, record it in the measuring cylinder.
- Measure the dry mass of the object using a balance.
- Plug the object's mass and volume into the formula for density. 

Pressure

- Pressure is the force you exert on a given area.

- Same force applied over a larger area = Lower pressure
- Same force applied over a smaller area = Higher pressure 
- Pressure and area are inversely proportional.
- In gases and liquids at rest, pressure at any point acts equally in all directions.
- In gases and liquids, the pressure increases with depth.
→ Pressure is higher at the bottom of the sea than at the surface. 
→ Pressure is lower high up in the atmosphere than close to Earth.
→ This happens because the weight of particles above acts on particles beneath it. 
- The pressure of a liquid isn't affected by the shape of a container. 

Pressure Difference in Liquids and Gases

- Pressure difference = Difference in pressure between 2 points in a liquid/gas.

More Pressure Equations

1. Given a fixed mass of gas at a constant temperature: 
- Pressure x Volume = Constant.  (pV = constant)

→ The diagram can work with any units ∴ It's a ratio.

2. In a sealed container (i.e., constant volume):