Energy Transfers I

Task 1 - Starter

Look at this presentation and answer the questions to see how much you understand about heat transfer.

Task 2

This hot drink contains energy.  The hot drink will cool down because it is transferring energy to its surroundings.  Energy will be transferred until it reaches the same temperature as its surroundings.

Now look at this cold drink.  Is energy being transferred here?  Discuss with the person next to you what you think is happening.

Your teacher will ask some of you to share your ideas with the class.

Now stick this sheet of notes in your exercise book and explain what you think will happen in the space provided.

Task 3

Lots of factors affect the rate at which energy is transferred.  Look at this presentation which explains some of the factors which can affect the rate of cooling.

       • The temperature difference between the object and its surroundings.

       • The size and shape of the object, and especially the surface area.

       • The type of material the object is made of.

       • What the object is in contact with.

Task 4

Complete these tasks and questions.  Answer all questions in full sentences.

1.) Write a list to summarise all the things that can change the rate at which heat energy is transferred.

2.) Explain how you could reduce the rate of heat energy transfer from a hot drink.

3.) Which cup of coffee will cool down faster?  Explain your answer.

4.) What can you say about the rate of heat energy transfer in an object that is at the same temperature as its surroundings?

Task 5 - Extension

Watch this video clip which explains how a vacuum flask keeps a drink warm.

Stick in this diagram of a vacuum flask and try these questions from the AQA textbook:

1.) Describe in detail how a vacuum flask keeps a drink warm.  You may wish to use the following terms in your explanation:

conduct          convection        thermal energy          transfer          vacuum          radiation          plastic          insulator          surface          shiny          matt/dull          light          dark          escape          evaporation          contained          free electrons         

2.) What kind of material would you put at the top of the vacuum flask (i.e. for the stopper)

3.) Why should you fill up a vacuum flask rather than half-fill it?  (higher tier)