RP5: Density

Question 1

What is the aim of this experiment?

Answer 1

• Determine the densities of regular and irregular solid objects and liquids. The volume of objects should be determined from the dimensions of regular shaped objects and by a displacement technique for irregularly shaped objects.

Question 2

Describe how you can calculate the density of regular objects (method)

Answer 2

1. Measure the length, height and width of the object, recording your values to the
   nearest millimetre.
2. Calculate the volume by multiplying the length, height and width, giving your value in
   cm³.
3. Measure the mass of the object, using the mass balance. Remember to reset the
   balance with nothing on the scales to reduce zero errors.
4. To calculate the density, use the equation:
   ρ = m
   V
   where ρ is the density, measured in (You must convert from to )

Question 3

Describe how you can calculate the density of irregular objects (method)

Answer 3

1. Fill the displacement can with room temperature water and align a measuring beaker
   with the spout. Make sure that the level of water lies below the level of the spout, but
   that there isn’t too much of a gap between the two levels.
2. Place the irregular shaped object slowly into the can, ensuring not to drop it from a
   height or cause it to splash.
3. Collect the displaced water and measure the volume of water displaced.
   The volume of water displaced will equal the volume of the object that caused the
   displacement.
4. Measure the mass of the object using a mass-balance.
5. Calculate the density of the irregular object, using the density equation in step 4 of
   the method above.

Question 4

Describe how you can calculate the density of liquid (method)

Answer 4

1. Measure the mass of an empty measuring beaker, using the mass-balance.
2. Pour 100cm³ of the liquid into the beaker.
3. Measure the combined mass of the beaker and the liquid.
4. To calculate the liquid’s mass, subtract the mass of the beaker from the mass of the
   combined beaker and liquid.
5. Calculate the density of the liquid using the density equation.

Question 5

List some safety precautions

Answer 5

• Take care handling glass equipment
• Clean any spillages of water

Question 6

What piece of equipment is used to measure the object’s mass? What must you do before using it?

Answer 6

• A digital balance
• Should be zeroed before placing the object on it to avoid a zero error

Question 7

Explain how you should fill the displacement can to get the most accurate results

Answer 7

• Fill the can until water starts to drip out of the spout and into the beaker
• Wait until the dripping just stops before submerging the object

Question 8

How does the density of solids and liquids compare?

Answer 8

• In general, solids are more dense than liquids since their particles are more tightly packed together (more mass per unit volume)