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Inspired by ‘The Lighthouse Keeper’s Lunch’ by Rhonda and David Armitage

© CCEA 2018

LearnIng IntentIon• Materials can exist in different states.

EquIpment• Four powders to test for ‘fizz’: sodium

bicarbonate (also called baking soda or bicarbonate of soda) and three others such as salt, sugar, flour, Epsom salts or Gelli Baff (available online)

• White distilled vinegar (a weak acid)

• Plastic beakers (or other small containers for mixing such as yoghurt pots)

• Plastic teaspoons

• Washing-up liquid

• Other liquids to investigate, such as pure lemon juice, apple juice, water, milk or fizzy soft drinks

• Food colouring

PreparatIonRead the chapter ‘Frobscottle and Whizzpoppers’ from ‘The BFG’ by Roald Dahl to the class.

Prepare four powders labelled A, B, C and D for testing. One of these powders must be the sodium bicarbonate; the other three can be from the selection in the equipment list.

Consider where to carry out the investigations. The potions may fizz over and cause spillages (which is all part of the fun!) so you could perhaps complete the investigation outside, or within a large tray/water tray.

Can you make your own fIzzy potIon?

KEY STAGE 2

STEM ENQUIRY

• Materials can be classified by their form – solid, liquid or gas (Change over Time).

• Materials can be changed by physical and/or chemical means to make new materials (Change over Time).

• Chemical change results in the formation of new substances or products

(Change over Time).

Always follow the health and safety policy in school and carry out a risk assessment.

Ways in which change occurs over both short and long periods of time in the physical and natural world. (Change over Time 2)

Inspired by ‘The BFG’ by Roald Dahl

2 © CCEA 2018

STEM ENQUIRY CONTINUED

Can you make your own fIzzy potIon?

Ideas to tryCan the class work out which powder the BFG uses to create the ‘fizz’ in his potions from the selection of powders found in the BFG’s cave?

Show the class the four powders A, B, C and D and a container of liquid (vinegar – a weak acid). Ask them to design an investigation to find out which powder will produce a liquid which will fizz. How can they ensure that it is a fair test? How will they record their observations?

SuggestIonMeasure out one level teaspoon of different powder into four containers. Systematically, add 20ml of liquid to each container. Observe what happens (using a hand lens if available) and record. Do some powders disappear (dissolve), turn the liquid cloudy, or fizz?

Powder Description Reaction in acid(cloudy appearance, dissolves, fizzes)

Sodium bicarbonate Powder

Salt Crystals

Sugar Crystals

Flour Powder

Gelli Baff Powder

Epsom salts Crystals

Crackle Baff Powder

Inspired by ‘The BFG’ by Roald Dahl

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3 © CCEA 2018

STEM ENQUIRY CONTINUED

Can you make your own fIzzy potIon?

When the class have discovered which powder causes the biggest fizz, try mixing one squeeze of washing-up liquid to the liquid and powder and observe what happens. Does stirring make a difference? What effect did it have on the potion? (It should create a thick, foamy fizz!).

Investigate adding the ‘fizz powder’ to other liquids, such as lemon juice, apple juice, milk, fizzy soft drinks and so on. Do they react in the same or different ways? Which liquid when mixed with the powder produced the best fizz? Why? (The one which fizzes the most is the most acidic.)

What happens if you use different quantities of liquid and ‘fizz powder’ and/or different shaped containers?

Allow time for each group to create their own potion with maximum fizz, perhaps adding small amounts of food colouring for impact.

ConsIder and dIscussWhy did the bicarbonate of soda cause the vinegar to fizz the most? (Sodium bicarbonate is an alkali that, when mixed with an acid, causes a chemical reaction, producing bubbles of carbon dioxide. Carbon dioxide is the gas which produces the fizz in our fizzy drinks.)

Other IdeasCreate a recipe book for all the fizzy potions invented by the class! Make a Frobscottle that you can safely taste using lemon juice, bicarbonate of soda, icing sugar and food colouring.

Inspired by ‘The BFG’ by Roald Dahl

Health and Safety Statutory Requirement Key Scientific Idea