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Chocolate changes

Topic: 6D Reversible & irreversible changes

This is a SATS revision exercise. Chocolate undergoes many changes from cacao pod to chocolate itself. Some of these changes are reversible and some are irreversible. But which ones?

In this activity children learn about reversible and irreversible changes. They correctly sequence the story of how chocolate is made. They label which of the changes are reversible. They use their knowledge to write a letter to a child in Ghana, explaining how cocoa beans are made into chocolate for Easter eggs.

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Try the Activity Learning Objective

Click to Download Chocolate changes Teacher notes
Chocolate changes Teacher notes

Click to Download Chocolate changes activity
Chocolate changes activity

   

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· That some changes that occur when materials are mixed cannot easily be reversed

Children will demonstrate this by completing the task on page 2 successfully.

· That heating some materials can cause them to change

Children will demonstrate this by completing the task on page 2 successfully.

· That cooling some materials can cause them to change

Children will demonstrate this by completing the task on page 2 successfully.

   
Curriculum Link

Science:
QCA unit 6D - Reversible and irreversible changes
· To describe changes that occur when materials are mixed
· To describe changes that occur when materials are heated or cooled
· About reversible changes, including melting and evaporating
· That non-reversible changes result in the formation of new materials

Scientific Enquiry- investigative skills
· Use first-hand experience to draw conclusions

ICT:
· Web links for further research on how chocolate is made

Literacy:
Writing Composition
· To collect information from a variety of sources and present it in one simple format

 
Running the Activity

Introducing the activity
· Display page 1 through a data projector or on an OHT. Describe how the cacao pod contains cocoa beans. Ask the children what sort of changes might happen to the cocoa beans in order to make chocolate. Use words such as separating, crushing, mixing, melting, pouring and cooling. Which of these are reversible?

Leading the main activity
· Display page 3 through a data projector or on an OHT. Print off copies for the children. Gather the children together to discuss where cocoa beans come from e.g. Ghana in Africa. Discuss why they do not grow in the UK. How suitable is our climate? What fruits and vegetables do we grow in the UK? Ask individual children to read out or describe each of the steps in the chocolate-making process. Invite comments or questions. Then ask the children to discuss, in pairs, whether each of the steps in the process is reversible or irreversible.

· Display page 2 through a data projector or on an OHT. Print off copies for the children. Supply scissors and glue plus blank sheets of paper so that children can cut and paste the steps of the process in the right order. Children should identify which of the changes are reversible by writing an ‘R' on or under the appropriate egg.

For more able children
1. Supply some but not all of the Easter eggs on page 2 and ask the children to outline the process by filling in the missing steps.
2. Provide a small card egg-shaped template and ask the children to construct and label their own chocolate-making process. Bi-directional arrows can be drawn between steps to illustrate reversible changes.

Optional practical activity for all

Q. What is the difference between white and dark chocolate?
Discuss the colour and the taste. What could be the reasons for the difference? More cocoa powder? More cocoa butter? What could we measure? Do they melt at the same temperature?
Aim of experiment: To find out if all chocolate melts at the same temperature.
Prediction: White chocolate melts at a higher temperature than dark chocolate OR white chocolate melts at a lower temperature than dark chocolate
Experiment: Provide a jug of water at 40oC and another jug at 50oC. Place a square or chocolate drop of each type of chocolate in a test tube or small container. Hold the test tubes in the jug of water at 40oC for a few minutes. What do you see? The white chocolate should start melting before the dark chocolate. Repeat the experiment using the jug at 50oC. Now both types of chocolate should melt.
Conclusion: White chocolate melts at a lower temperature than dark chocolate.
Why: White chocolate contains more cocoa butter (melting point 38oC) so it melts at a lower temperature than dark chocolate.
Points for discussion: How to make the test fair. How are we measuring the temperature of the water? Is the size of the chocolate drops the same in each case? How else could we be sure the amount of chocolate is the same? Weigh it? Does it make any difference if we leave it in the water longer?

· Ask the children to write a letter to a child in Ghana. They should explain how the cocoa beans that are grown in Ghana are brought to the UK and converted into chocolate. They should discuss how we eat chocolate eggs at Easter so there is a great demand for chocolate at this time.

 
Web Links

Divine chocolate
From bean to bar - description of how chocolate is made from cocoa beans from Ghana

Cadbury
Resources, games and information about Cadbury's chocolate and its factory

Exploratorium
Sweet lure of chocolate - the chocolate-making process

How Stuff Works
Chocolate making and photos

Venezuelatuya
Photos of the different stages of chocolate making (in Spanish)

Teaching Ideas
Practical science investigation worksheet to design an experiment on the melting of chocolate

Teaching Ideas
How to design a ‘wicked' science investigation - gives children clear advice about how they should plan and implement a science investigation.

 
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