P6 Molecules and matter

Question 1

Define density

Answer 1

The density of a substance is defined as its mass per unit volume.

Question 2

How to calculate the density of a substance

Answer 2

density = mass / volume
density (kg/m3)
mass (kg)
volume (m3)

Question 3

Measuring the density of a regular solid object

Answer 3

• To measure the mass of the object, use an electronic balance. Make sure the balance reads zero before you place the object on it
• To find the volume of a regular solid, such as a cube or cuboid, measure its dimensions using a millimetre ruler. Use the measurements and the equation volume = length x width x depth to calculate the volume
• Use the equation density = mass / volume to calculate the density

Question 4

Measuring the density of an irregular solid object

Answer 4

• To measure the mass of the object, use an electronic balance. Make sure the balance reads zero before you place the object on it
• For a small irregular solid, lower it on a thread into a measuring cylinder partly filled with water. Work out the volume of the object by the rise in the water level
• Use the equation density = mass / volume to calculate the density

Question 5

Measuring the density of a liquid

Answer 5

• Use a measuring cylinder to measure the volume of a particular amount of the liquid
• Measure the mass of an empty beaker using a balance. Remove the beaker from the balance and pour the liquid from the measuring cylinder into the beaker
• Use the balance again to measure the total mass of the beaker and the liquid
• Calculate the mass of the liquid by subtracting the mass of the empty beaker from the total mass of the beaker and the liquid
• Use the equation density = mass / volume to calculate density

Question 6

Differences between the three states of matter

Answer 6

Solids:
- no flow
- fixed shape
- fixed volume
- density much higher than that of gas

Liquids:
- can flow
- fits container shape
- fixed volume
- density much higher than that of gas but lower than solids

Gases:
- can flow
- fills contianer
- volume can be changed
- density lower than a solid or liquid