Molecules and matter

Density is mass per unit volume.

mass = density x volume

Pure water's density is 1000kg/m^3 but floatable objects have a density less than 1000kg/m^3. 

To measure a mass of a regular object, use an electronic balance. To find its volume, measure its dimensions with a ruler and multiply them together.

For a small irregular solid, lower it on a thread into a measuring cylinder partly filled with water and find out the rise in water level.

To measure the density of a liquid, use a measuring cylinder to measure the volume and measure an empty beaker's mass with a balance. Pour the liquid from the measuring cylinder into the beaker. Use the balance to measure this mass and subtract the empty beaker's mass from the beaker and liquid's mass. 

Use the equation for density.

Changes of state are physical changes. When a substance changes state, the number of particles and therefore mass stays the same.

When temperature increases, particles move faster. 

In a solid, particles are held next to each other in a fixed position and they vibrate about in their fixed positions. 

In a liquid, the particles are in contact with each other and move at random.

In a gas, particles move about at random and move faster and are further apart than a liquid. 

Gases have the most kinetic energy and solids have the least kinetic energy but they have the most potential energy and gases have the least potential energy.

For any pure substance undergoing a change of state, the temperature is the same. 

The freezing point is  the same as the melting point and the boiling point is…