P 6.1 How does energy transform matter?

Define density. [1 Mark]

A volume of air measuring 3.0 m³ has a mass of 3.9 kg.

Calculate its density. [2 Marks]

Georgina does an experiment to test the hypothesis ‘the reason why a solid floats or sinks in a liquid depends upon both the density of the solid and the density of the liquid’.

She was given blocks of rubber and wood and bottles of maple syrup and baby oil.

Georgina concludes that the density of both the solid and the liquid affects whether it floats or sinks.

Use the data to justify Georgina’s conclusion.

The diagram shows a common type of electric heater. It contains oil which is heated by an electrical element.

Show that more than 700 000 J of energy is needed to heat the oil from 20 °C to 120 °C.

Use the equation:

change in internal energy = mass × specific heat capacity × change in temperature [2 Marks]

An electrical heater of power 60 W is placed into 200 g of water at 100 °C. Calculate the
mass of water that evaporates in a time of 200 s.

(Specific latent heat of vaporisation of water = 2300 J/g)

1 Ethanol is produced when sugar is fermented with yeast. The fermentation products are
distilled to extract the ethanol. Calculate the energy needed to distill 3 kg of ethanol from a mixture that is at a constant 78 °C. Give your answer to 2 significant figures.

Water has a density of 1000 kg/m³. What is the mass of water needed to fill a rectangular
bath 175 cm long, 75 cm wide, and 50 cm deep?

1 A block of brass measures 14 cm by 12 cm by 5 cm. The density of brass is 8.6 g/cm³.
Calculate the mass of the block. Give your answer in kg.

a- Write down what you know, with the units.

b- Calculate the volume of the block.

c- Write down the equation that relates density, mass, and volume.

d- Rearrange the equation to make mass the subject of the equation.

e- Substitute the quantities into the equation and calculate the mass of the block.

f- What is the mass of the block in kg?

Calculate the energy needed to raise the temperature of a 2 kg block of iron from 20 °C to 40 °C.

A student uses a 38 W immersion heater to heat a 800 g copper block from 20 °C to 45 °C.

a- Calculate the energy transferred to the copper block.

b- Calculate the time taken to for the 36 W immersion heater to heat the block from
20 °C to 45 °C.