OCR GCSE Combined Science
Density can be calculated using the equation: density = 
Which row of the table is correct?
| Mass (kg) | Volume (m3) | Density (kg / m3) | |
| A | 6.0 | 3.0 | 2.0 |
| B | 6.0 | 3.0 | 3.0 |
| C | 6.0 | 3.0 | 9.0 |
| D | 6.0 | 3.0 | 18.0 |
Cool packs are used to treat injuries by cooling the injured area.
Cool packs are stored in a freezer. The chemical they contain is solid in the freezer, but it melts on contact with warm skin.
When the cool pack melts, the density of the chemical inside decreases.
Explain why the density decreases.
Use ideas about particles.
The cool pack contains 0.125 kg of a chemical with a specific latent heat of 425 000 J / kg.
Calculate the energy needed to completely melt the chemical in the cool pack.
Give your answer to 3 significant figures.
Use the Equation Sheet.
The table gives data on three chemicals which could be used in a cool pack.
| Chemical | A | B | C |
| Melting point (°C) | 60 | 0 | –5 |
| Specific latent heat (J / kg) | 510 000 | 334 000 | 425 000 |
Explain why most cool packs use chemical C.
A jeweller has a ring.
They also have some water, a measuring cylinder, and a digital balance.
Explain how they could use these items to find the density of the ring.
The jeweller knows that the ring is either made of copper or gold, or an alloy of copper and gold.
The table shows some data about copper and gold.
| Copper (solid) | Gold (solid) | |
| Density (kg / m3) | 900 | 1800 |
The jeweller finds that the density of the ring is 1600 kg / m3.
What is the most likely composition of the ring?
Tick (✓) one box.
Explain your answer to (i).
The table shows some data about liquid copper and liquid gold.
| Copper (liquid) | Gold (liquid) | |
| Density (kg / m3) | 800 | 1700 |
Explain why the densities of solids are greater than the densities of liquids.
Use ideas about particles and volume.
Which two instruments are used to measure the density of a rectangular glass block?
A A measuring cylinder and a ruler
B A protractor and a ruler
C A protractor and an electronic balance
D A ruler and an electronic balance
A teacher measures the specific latent heat of ice using this method:
• Pour water at 30 °C into a beaker.
• Add the ice cube to the beaker of water.
• Measure the final temperature of the water after the ice cube melts.
Here are the first set of results from the experiment.
Starting temperature of ice cube = 0 °C Mass of water = 0.2 kg Starting temperature of water = 30 °C Final temperature of water = 14 °C The specific heat capacity of water = 4200 J / kg °C
Calculate the change in thermal energy of the water.
Use the Equation Sheet.
Give your answer to 2 significant figures.
The ice must be dried with a paper towel before starting the experiment.
Suggest why.
Describe how the terms specific latent heat and specific heat capacity are different.
The teacher then measures the density of an ice cube.
This is the method they use:
• Measure the mass of the ice cube.
• Place the ice cube in a measuring cylinder containing water.
• Measure the increase in volume of the water after the water has settled.
• Divide the mass by the increase in volume to measure density.
The teacher’s method does not give an accurate value for the density of ice.
Suggest why.
Suggest a change to the method which would give a more accurate value for the density of ice.
Which substance listed in the table has the highest density ?
| Substance | Mass (kg) | Volume (cm3) |
| A | 1.0 | 1.5 |
| B | 1.0 | 3.0 |
| C | 1.0 | 4.5 |
| D | 1.0 | 6.0 |
Which substance listed in the table has the highest density?
| Substance | Mass (kg) | Volume (cm3) |
| A | 0.5 | 1.5 |
| B | 0.5 | 3.0 |
| C | 1.0 | 1.5 |
| D | 1.0 | 3.0 |
Place the events in the order they occurred.
Write the numbers in the boxes below. One has been done for you.
The events were peer reviewed and communicated to others.
Suggest why both are important in science.
Table 16.1 gives the density of different materials.
Describe any trends in the data in Table 16.1.
Explain the difference in density between solids and liquids.
You may draw diagrams to help your answer.
Table 16.2 gives some information about ethanol and water.
The specific latent heat of vaporisation is the energy transferred when 1 kg of a substance changes from liquid to gas.
Calculate the amount of energy needed to evaporate 0.2 kg of ethanol.
Use Table 16.2 and an equation from the Data Sheet to help you.
The energy needed to heat 1 kg of water by 1 °C is 4200 J.
The energy needed to evaporate 1 kg of water is 2 256 000 J.
This is much more than 4200 J. Explain why.
Place the events in the order they occurred.
Write the numbers in the boxes below. One has been done for you.
The events were peer reviewed and communicated to others.
Suggest why both are important in science.
Table 11.1 gives the density of different materials.
Describe any trends in the data in Table 11.1.
Explain the difference in density between solids and liquids.
You may draw diagrams to help your answer.
Table 11.2 gives some information about ethanol and water.
The specific latent heat of vaporisation is the energy transferred when 1 kg of a substance changes from liquid to gas.
Calculate the amount of energy needed to evaporate 0.2 kg of ethanol.
Use Table 11.2 and an equation from the Data Sheet to help you.
The energy needed to heat 1 kg of water by 1 °C is 4200 J.
The energy needed to evaporate 1 kg of water is 2 256 000 J.
This is much more than 4200 J. Explain why.
15* A turbine contains a rotating blade.
Fig. 15.1 is a diagram of a wind turbine and Fig. 15.2 is a diagram of a water (tidal) turbine.
A volume of air (wind) or water (tidal) flows through the turbine every second.
Some of the kinetic energy of the air or water is transferred.
This table gives information about wind and tidal turbines:
| Wind energy | Tidal energy | |
| Density of air or water (kg / m3) | 1.2 | 1020.0 |
| Typical air or water speed (m / s) | 5 | 5 |
| Volume of air or water through turbine in 1 second (m3) | 38 000 | 8 |
| Efficiency | 0.60 | 0.75 |
Compare the advantages and disadvantages of using each type of turbine.
Use kinetic energy calculations to support your answer.
A student is given a solid metal cube.
Explain how the student can use a ruler to calculate the volume of the metal cube.
The metal cube has a volume of 125 cm3 and a mass of 850 g. (ii)
Calculate the density of the metal cube.
Use the equation: density = mass ÷ volume
Density =........ g / cm3
The student wants to calculate the density of a stone. The stone has an irregular shape.
Suggest one piece of apparatus that she can use to measure the mass of the stone.
Suggest one piece of apparatus that she can use to measure the volume of the stone.
A student has two metal cubes, A and B, as shown in Fig. 12.1.
Each side of metal cube A is 1.0 cm. Each side of metal cube B is 2.0 cm.
Both metal cubes have the same mass. The density of metal cube A is 16 g / cm3.
Calculate the density of metal cube B.
Use the equation: density = mass ÷ volume
Density =........ g / cm3
Metal cube A sinks when placed in water.
Explain why.
The resultant force on the spring is zero.
Explain why.
Use your answer to 12(b)(i) to help you.
More than one force is required to stretch the spring.
Describe what happens if only one force is applied.
The student removes cube A and places another cube, cube C, on the spring.
The extension of the spring due to cube C is 0.04 m.
The spring constant of the spring is 30 N / m.
Calculate the weight of cube C.
A student has a wooden cube.
Explain how she could find the density of the wooden cube.
Include the measurements needed.
When a material changes state, its density changes.
Explain how.
Use ideas about particles.
You may draw diagrams of solids, liquids and gases to help.
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