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"Children should use enquiry skills in context. These up-to-the-minute stories will captivate them"

Anne Goldsworthy
Primary Science Expert

Topic: Physical changes

Many students will have seen the new film of ‘Charlie and the Chocolate Factory', the theme for this activity. Students are asked to work out a recipe for a new chocolate bar. In particular, how can they get solid biscuits, raisins and silver balls to stay solid when chocolate needs to melt to make a bar of the right shape? Students further apply their knowledge and understanding of solids, liquids, melting and solidifying by working out how to make a solid cake with a liquid sauce in an extension activity.

chocolate factory activity	chocolate factory teachers notes doc

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· That some changes can be reversed (level 3)

Students will demonstrate this by creating a recipe for a chocolate bar that requires the melting and solidifying of chocolate

· (Extension activity)
That some changes cannot be reversed, and classify changes in this way (level 3). To use knowledge about some reversible and irreversible changes to make simple predictions about whether other changes are reversible or not (level 4).

Students will make predictions orally - and possibly in writing - and use their knowledge to create a recipe for a solid chocolate cake and liquid chocolate sauce.

Science:
QCA 4d - Solids, liquids and how they can be separated
· That the same material can exist as both solid and liquid
· That liquids can be changed to a solid by cooling and this is freezing or solidifying
· That a solid can be changed to a liquid by heating and this is melting
· That melting and solidifying or freezing are changes that can be reversed and are the reverse of each other

QCA 6d - Reversible and irreversible changes
· That heating some materials can cause them to change
· That cooling some materials can cause them to change

Scientific Enquiry- investigative skills
· Use first-hand experience to draw conclusions
· Think about what might happen when deciding what to do and decide what equipment to use.

Literacy text level
· To write Instructions
· To write recipes using a range of organizational devices eg lists, dashes, commas for lists in sentences, recognising the importance of correct sequence

What you need to do

Introducing the activity
· Display the cartoons on pages 1 and 2 through a data projector or on an OHT. Read through the cartoon, perhaps with students taking the roles of the characters.

· Display page 3. The first task is to look at the properties of the ingredients - through discussion, get students to identify those that are solid and those that are liquid. Also, discuss which of the words in the big box will correctly complete the labels next to the cooker (melts) and the fridge (solidifies). Then add labels to the screen or ask students to label paper copies of page 3.

Discussion Starters
o What happens to chocolate if it is left on a windowsill, in the car, their pocket on a hot day?
o What happens if you put a melted chocolate bar in the fridge?
o What would happen if you held a chocolate button in your hand for a minute?
o What are some ways of melting chocolate? (microwave/over boiling water)
o What other materials melt? (ice cream, wax running down side of a candle)
o When have students seen water freeze? What conditions are necessary?
o How can you make ice melt?

Leading the main activity

1. Optional practical activity

· Hold a chocolate button in your hand for a minute or melt a handful of chocolate buttons in bowl over pan of boiling water
(You do not need to keep the water boiling to melt buttons, just boil a kettle and put the boiling water in a pan under a bowl and the buttons will melt very quickly).
· Revise the vocabulary above as you melt the button(s).
OR
· Give each student a chocolate button to hold in their hand!

· Give students frozen ice pops or ice cubes to leave on their desks
· Leave melted chocolate to solidify in the room, or ice pops to solidify in a freezer. (If spread reasonably thinly melted chocolate will solidify in 30 minutes at room temperature on a hot day.)

2. Whole Class Discussion

· Ask students to predict what will happen to melted chocolate if left at room temperature or in the fridge.
· Establish that it will solidify and therefore change from a liquid to a solid
· Use the phrase ‘reversible change'

3. Explain the challenge

· Go back to pages 1, 2 and 3 to remind students that they must work out how to make a chocolate bar that contains some or all of the solid ingredients shown on page 3. Ask students to work in pairs.
· Tell students they must lay out their recipe clearly, giving a list of ingredients (they can choose their own secret ingredients!), a list of equipment, and explaining the method clearly, using illustrations/diagrams to show the method.
· Page 4 is a writing frame to help lower achieving students record their recipes clearly.

4 Optional practical activity outcomes!

· Choose one or a number of winning entries to create their chocolate bar.
OR
· Give each pair a paper cake case and a choice of solid ingredients to put in the bottom. The teacher melts some chocolate and each pair has a spoonful to put in their case on top of the solid ingredients.

5 Extension activity on reversible and irreversible changes:

· Read through the cartoon strip on page 5 with students taking on the roles of the journalist and Freddie Fabbo.

· Explain that the task is to work out how to make a solid chocolate cake with a chocolate sauce that stays runny.

· Establish that the uncooked cake mix is a liquid and that when it is cooked (heated) it becomes a solid. Establish that making the cooked cake is an irreversible change.

· Ask students how they would make a chocolate sauce that remains runny. Remind them of previous learning about chocolate buttons, which when heated melt and become liquid and when cooled return to being a solid again.

· Get students to invent a recipe for a chocolate sauce that will remain a liquid and write a recipe for this. Students must use the words ‘solid, liquid, heat, melt and solidify' in writing their recipe. [NOTE (Delia Smith makes chocolate sauce with 225g chocolate melted with 3 tablespoons of water. Nigel Slater makes one with 200g of melted toblerone. He then stirs in 30 g butter and 100ml of whipping cream!!)]

Warner Bros
The film's official web site, for pictures and a trailer

Amazon
Synopsis of the plot of the book

BBC Science
The science of chocolate

Exploratorium
The sweet lure of chocolate

Australian Broadcasting
Chocolate cake addiction is real

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