Specific heat capacity

Some types of kettle are battery powered.

The kettle contains 0.50 kg of water at 20 C.

Calculate the minimum change in thermal energy needed to raise the temperature of the water to 100 C.

The specific heat capacity of water is 4200 J / kg C.

Use the equation:

change in thermal energy = mass specific heat capacity change in temperature

Explain why the actual amount of thermal energy needed to raise the temperature of the water would be greater than the calculated value in (a)(ii).

What is the time taken for the temperature of the water in cup B to decrease from 80 C to 60

Time taken =........ minutes

One cup is made of metal and the other cup is made of plastic.

The metal cup is a better conductor than the plastic cup.

Which cup, A or B, is made of metal?

Give a reason for your answer using information from the graph.

Suggest two variables the students should control in their experiment.

The students wrap the cups in thermal insulation and repeat the same experiment, as shown in the diagram.

Predict how these new temperature readings after 5 minutes compare to the original results on the graph.

Give a reason for your answer.

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.

A student does an experiment to measure the power rating of a Bunsen burner.

The diagram shows their experiment.

This is the method they follow:

• Pour 0.2 kg of water into a beaker.

• Increase the temperature of the water using the Bunsen burner.

• Measure the time taken for the temperature of the water to increase by 50 °C.

Suggest a way to measure the time taken.

The mass of the water is 0.2 kg. The temperature change is 50 °C.

The specific heat capacity of water is 4200 J / kg °C.

Calculate the thermal energy transferred to the water.

Use the Equation Sheet.

The student repeats the experiment. They say that the energy transferred by the Bunsen burner is 40 000 J after 200 s.

Calculate the power of the Bunsen burner.

Another student repeats the experiment for two Bunsen burners A and B.

The graph shows the time taken for the temperature of 0.2 kg of water to increase by 50 °C.

The student says, ‘Bunsen burner A has the highest power.’

Explain how the graph shows this.

The manufacturer says, ‘The line on the graph for Bunsen burner B is not accurate. The power of the Bunsen burners should be the same.’

Both Bunsen burners are working correctly.

What did the student do wrong when testing Bunsen burner B ?

Tick (✓) one box.

Three students A, B and C do an experiment to measure the power rating of a Bunsen burner.

The diagram shows their apparatus.

This is the method they follow:

• Pour 0.2 kg of water into a beaker.

• Increase the temperature of the water using the Bunsen burner.

• Measure the temperature of the water every 30 seconds.

The graph shows student A ’s results.

Student A uses point P on the graph to calculate the gradient of the line of best fit.

Explain why student A ’s calculation is incorrect.

Calculate the gradient of the line of best fit on the graph. Give your answer to 2 significant figures.

Gradient =........ °C / s

What is the significance of the y intercept of the line on the graph?

What is the significance of the gradient of the line on the graph?

Student B repeats the experiment. The gradient of their line of best fit is 0.25 °C / s. The specific heat capacity of water is 4200 J / kg °C.

Use student B ’s value to calculate the thermal energy transferred to 0.2 kg of water after 200 s.

Use the Equation Sheet.

Student C also repeats the experiment.

They say the thermal energy transferred is 32 000 J after 200 s.

Use student C ’s value to calculate the power of the Bunsen burner.

Use the Equation Sheet.

Describe the difference between specific heat capacity and specific latent heat.

A small heater is used to increase the temperature of different liquids. The graph shows how the temperature rise changes due to the varying specific heat capacities of these liquids.

Using the graph, describe the relationship between temperature rise and specific heat capacity.

A liquid has a specific heat capacity of 1600 J / kg °C.

Use the graph to estimate the temperature rise of the liquid.

State one assumption you made when answering (b)(ii).

A student calculates the specific heat capacity of water. The student does one experiment and gets this result:

• Student’s value = 4250 J / kg °C.

• Textbook value = 4200 J / kg °C.

Complete the sentence below. Use one of the words.

Accurate Precise Reliable Repeatable Systematic

The student’s value is ………………………………………...

Student A uses the electric hot plate in Fig. 11.1 to increase the temperature of water in a saucepan.

Fig. 11.1

Student A wants to calculate the thermal energy transferred to the saucepan of water.

These are the steps in their method:

1 Measure the volume of water with a balance. 2 Measure the starting temperature of the water with a thermometer. 3 Use the equation:

change in thermal energy = mass specific heat capacity change in temperature

Student A ’s method is incorrect.

Identify the two mistakes the student has made and write down the correction for each mistake.

Student A suggests wrapping insulation around the saucepan in Fig. 11.1.

Suggest another way student A can improve their experiment.

Student B uses the immersion heater in Fig. 11.2 to increase the temperature of water in a beaker.

Fig. 11.2

Describe an experiment to measure the energy transferred to the immersion heater, using the equipment in Fig. 11.2.

In your answer include:

• a method

• a circuit diagram

• an equation from the Data Sheet

• the symbol for a resistor to represent the immersion heater in your circuit.

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.

This question is about energy changes in different situations.

Define braking distance.

• The braking distance is 6 m.

• The thinking distance is 6 m.

Calculate the stopping distance.

Explain how Fig. 12.1 shows the law of conservation of energy.

Complete these sentences about energy stores.

You can use each word once, more than once, or not at all.

chemical gravitational kinetic magnetic nuclear thermal

• A student rolls a ball up a hill. The ball stops at the top of the hill.

A kinetic store decreases. A........ store increases.

• A car accelerates.

A chemical store decreases. A........ store increases.

• Uranium fuel rods are used in a power station to produce electricity.

An electric kettle boils water.

A nuclear store decreases. A........ store increases.

A student measures the increase in the temperature of a metal block when it is heated.

Fig. 12.2 shows the apparatus that the student uses.

Complete the missing label on the diagram.

• The specific heat capacity of the block is 500 J / kg °C.

• The mass of the block is 0.5 kg.

• Its temperature increases by 20 °C.

Calculate the energy transferred to the block.

Use an equation from the Data Sheet to help you.

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.

Two students are making waves using a dripping tap.

The water droplets create waves in the water in a bowl.

Describe the change in energy stores as a water droplet

• falls from the tap:........

• lands in the water in the bowl:........

The students count the number of droplets hitting the water in the bowl.

In 20 seconds, 5 droplets hit the water in the bowl.

Calculate the frequency of the waves produced.

How can the students tell that the water waves travel but the water does not?

One of the students says, ‘the temperature of the water in the bowl increases when the water drips into it’.

• 1 droplet of water transfers 5.04 × 10⁻⁴ J of energy as it lands in the bowl.

• The bowl contains 3 kg of water.

• The specific heat capacity of water is 4200 J / kg °C.

Calculate the temperature rise of the water in the bowl when 1 droplet of water lands in it.

Use an equation from the Data Sheet to help you.

In 1847, James Joule did experiments at the bottom of a waterfall.

He was unable to measure the temperature rise of the water.

Suggest two reasons why.

A student measures the temperature of a beaker of water as it cools down.

The graph in Fig. 16.1 shows how the temperature changes with time.

Calculate the rate of temperature change over the 5 minutes.

Rate of temperature change =........ °C / minute

Describe, in detail, how the temperature changes over the 5 minutes.

The beaker contains 0.2 kg of water.

The specific heat capacity of water is 4200 J / kg °C.

Calculate the change in thermal energy in the water after 5 minutes.

Give your answer to 1 significant figure.

Use an equation from the Data Sheet to help you.

Describe the change in energy stores as the water cools down.

The student is given some insulation. She wraps the insulation around the sides of the beaker and repeats the experiment.

Add another line to the graph in Fig. 16.1 to show how the temperature may change

when the beaker is wrapped with insulation.

State one thing the student can do to reduce the rate of cooling further.

A student measures the temperature of a beaker of water as it cools down.

The graph in Fig. 11.1 shows how the temperature changes with time.

Calculate the rate of temperature change over the 5 minutes.

Rate of temperature change =........ °C / minute

Describe, in detail, how the temperature changes over the 5 minutes.

The beaker contains 0.2 kg of water.

The specific heat capacity of water is 4200 J / kg °C.

Calculate the change in thermal energy in the water after 5 minutes.

Give your answer to 1 significant figure.

Use an equation from the Data Sheet to help you.

Describe the change in energy stores as the water cools down.

The student is given some insulation. She wraps the insulation around the sides of the beaker and repeats the experiment.

Add another line to the graph in Fig. 11.1 to show how the temperature may change

when the beaker is wrapped with insulation.

State one thing the student can do to reduce the rate of cooling further.

Which row, A, B, C or D shows the largest change in thermal energy?

A scientist does an experiment to measure the energy transferred to water.

She uses an immersion heater to increase the temperature of the water.

The scientist uses this apparatus:

• A beaker

• An immersion heater

• A stirring rod

• A 12 V battery and wires.

What two other pieces of apparatus does the scientist need for this experiment?

Explain how the scientist could reduce energy transfer to the surroundings.

The immersion heater is placed at the bottom of the beaker.

Suggest why.

The heater is connected to a battery. When the heater is turned on, energy is transferred.

Describe this energy transfer.

Use ideas about energy stores.

The current through the heater is 3.8 A. The potential difference across the heater is 9.0 V.

Use the equation: Power = Potential difference × Current

Calculate the power of the immersion heater.

The scientist writes down more information about her experiment.

• Mass of water = 150 g

• Specific heat capacity of water = 4200 J / kg °C

• Temperature increase of water = 10 °C

Calculate the change in thermal energy of the water.

Which of the following is a definition for specific heat capacity in physics?

A Energy needed to increase the temperature of 1 g of material by 1 °C.

B Energy needed to increase the temperature of 1 kg of material by 1 °C.

C Energy needed to increase the temperature of 1 g of material by 10 °C.

D Energy needed to increase the temperature of 1 kg of material by 10 °C.

13* A student removes a material from a freezer and heats it up.

He uses a heater with a constant power output. He then plots a heating curve of the material as its temperature rises.

Describe and explain what the graph tells us about the material being heated.

A scientist completes an experiment to determine the specific heat capacity of water.

She uses an immersion heater to increase the temperature of water in a beaker.

Suggest two ways to ensure the scientist obtains accurate results.

The scientist measures the temperature of the water every 60 seconds.

She plots her results.

Is there a random error in this experiment?

Explain your answer.

The scientist thinks the point labelled B on the graph is an anomaly.

Is she correct? Explain your answer.

Calculate the gradient (slope) of the graph.

Answer =........ °C / s

The scientist writes down more results.

• 0.1 kg of water used

• Power of immersion heater = 12.8 W

Use the equations:

Energy transferred = Power × Time

Change in thermal energy = Mass × Specific heat capacity × Change in temperature

Calculate the specific heat capacity of water.

Use the results and the gradient you calculated in part (c)(i).

Answer =........ J / kg °C