Particle Model
Density:
• Density is a measure of the ‘compactness’ of a substance It relates the mass of a substance
to how much space it takes up.
• A dense material has its particles packed tightly together. The particles in a less dense Mass
material are more spread out – if you compressed the material, its particles would move
closer together, and it would become more dense.
• The equation for density is: Density Volume
"#$$ ('()
• 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 (𝑘𝑔/𝑚! ) = !
*+,-". (" )
• Solids
1. Strong forces of attraction hold the particles close together in a fixed, regular arrangement. The
particles don’t have much energy, so they can only vibrate about their fixed positions. The density
is generally highest in this state as the particles are closest together.
• Liquids
1. There are weaker forces of attraction between the particles. The particles are close together,
but can move past each other, and form irregular arrangements. They have more energy than
the particles in a solid – they move in random directions at low speeds. Liquids are generally less
dense than solids.
• Gases
1. There are almost no forces of attraction between the particles. The particles have more energy
than in liquids and solids – they’re free to move, and travel in random directions at high speeds.
Gases are generally less dense than liquids – they have low densities.
• To find the density of a solid object:
1. Use a balance to measure its mass
2. If it’s a regular solid, start by measuring its length, width and height with an appropriate piece of
equipment (e.g. a ruler). Then calculate its volume using the relevant formula for that shape.
3. For an irregular solid, you can find its volume by submerging it in a eureka can filled with water
the water displaced by the object will be transferred to the measuring cylinder.
4. Record the volume of water in the measuring cylinder. This is the volume of the object.
5. Plug the object’s mass and volume into the formula above to find its density.
• To find the density of a liquid:
1. Place a measuring cylinder on a balance and zero the balance
2. Pour 10ml of the liquid into the measuring cylinder and record the liquids mass.
3. Pour another 10ml into the measuring cylinder, repeating the process until the cylinder is full
and recording the total value and mass each time.
4. For each measurement, use the formula to find the density.
5. Finally take an average of your calculated densities. This will give you a value for the density of
the liquid.
Internal Energy:
• Energy stored by the particles (atoms and molecules) of a substance.
• It is the sum of the kinetic energy and potential energy of all the particles in a system.
Density:
• Density is a measure of the ‘compactness’ of a substance It relates the mass of a substance
to how much space it takes up.
• A dense material has its particles packed tightly together. The particles in a less dense Mass
material are more spread out – if you compressed the material, its particles would move
closer together, and it would become more dense.
• The equation for density is: Density Volume
"#$$ ('()
• 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 (𝑘𝑔/𝑚! ) = !
*+,-". (" )
• Solids
1. Strong forces of attraction hold the particles close together in a fixed, regular arrangement. The
particles don’t have much energy, so they can only vibrate about their fixed positions. The density
is generally highest in this state as the particles are closest together.
• Liquids
1. There are weaker forces of attraction between the particles. The particles are close together,
but can move past each other, and form irregular arrangements. They have more energy than
the particles in a solid – they move in random directions at low speeds. Liquids are generally less
dense than solids.
• Gases
1. There are almost no forces of attraction between the particles. The particles have more energy
than in liquids and solids – they’re free to move, and travel in random directions at high speeds.
Gases are generally less dense than liquids – they have low densities.
• To find the density of a solid object:
1. Use a balance to measure its mass
2. If it’s a regular solid, start by measuring its length, width and height with an appropriate piece of
equipment (e.g. a ruler). Then calculate its volume using the relevant formula for that shape.
3. For an irregular solid, you can find its volume by submerging it in a eureka can filled with water
the water displaced by the object will be transferred to the measuring cylinder.
4. Record the volume of water in the measuring cylinder. This is the volume of the object.
5. Plug the object’s mass and volume into the formula above to find its density.
• To find the density of a liquid:
1. Place a measuring cylinder on a balance and zero the balance
2. Pour 10ml of the liquid into the measuring cylinder and record the liquids mass.
3. Pour another 10ml into the measuring cylinder, repeating the process until the cylinder is full
and recording the total value and mass each time.
4. For each measurement, use the formula to find the density.
5. Finally take an average of your calculated densities. This will give you a value for the density of
the liquid.
Internal Energy:
• Energy stored by the particles (atoms and molecules) of a substance.
• It is the sum of the kinetic energy and potential energy of all the particles in a system.
