Conduction, convection and radiation

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.

Material X has a high thermal conductivity. Material Y has a low thermal conductivity.

Each material is wrapped around a different identical beaker containing water at 60 C.

Which beaker of water would have the smallest temperature decrease if all other variables are kept the same?

A 1 layer of material X wrapped around the beaker

B 1 layer of material Y wrapped around the beaker

C 2 layers of material X wrapped around the beaker

D 2 layers of material Y wrapped around the beaker

How can a house be heated more efficiently?

A Increase the temperature in the house.

B Turn the radiators on for a longer time.

C Use insulation with a greater thickness.

D Use insulation with a higher thermal conductivity.

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.

A teacher adds 200 cm³ of warm water to a beaker. 10

He wraps the beaker in insulation. He measures the temperature drop after 10 minutes.

The table shows the results of four different experiments A, B, C and D.

Which experiment gives the lowest rate of cooling?