Can custard act like a solid?

Learning objectives

• To find out how custard molecules behave when force is applied to its surface.
• To understand why custard doesn’t behave like a liquid should.

Where this fits into the Technology syllabus
Key Stage 3 Strategy, Making high quality products sub skill.
“ pupils should apply their knowledge of the characteristics of materials when creating solutions”

Content

• This lesson or the first part of the lesson needs to take place in a Food Technology room as the pupils need access to a cooker.
  
• At the start of the lesson, pupils are asked what form custard takes (a solid, liquid or gas?) and whether it can behave like a solid, and withstand an object sinking through it.
  
• Before pupils can experiment with this theory they need to mix some custard and leave it to set.
• The custard must be mixed under close supervision of staff and can be produced in pairs or small groups to make this manageable.
  
• The recipe and instructions for mixing the custard are on the PowerPoint presentation.

WARNING; The boiling of the water (and it needs to be boiling for the experiment to work) must be supervised carefully and poured by a member of staff into the custard powder. (support from other staff would be beneficial at this point). If the custard does not thicken when stirred it might need to be brought back to boiling point in a microwave till it thickens.

The mixed custard needs to be poured into a tray or grill pan that allows for the custard to sit at least 2 inches deep.The custard then needs to be left somewhere cool to set.
Whilst the custard is setting, use the remainder of the PowerPoint to explain how the molecules in the custard behave when an object makes contact with the surface firmly and at some speed. Pupils then slap the custard as hard as they can to see if it will withstand the impact to see if this is the case.

Resources

• Old clothes and an apron
• Custard powder
• Pan
• Cooker
• Table spoon
• Measuring jug
• Shallow tray/grill pan
• Access to computer, whiteboard or projector for PowerPoint.
• Access to outdoor area where custard experiment can be carried out.

Safety Issues.

• Pupils or staff will be using boiling water to make the custard and should be supervised and instructed accordingly.
• If a cooker is used to boil the water pupils should be advised and supervised accordingly and care taken to ensure the appliance is turned off.
• At several points in the exercise pupils will use liquids, this could lead to slipping hazards and pupils should be warned of this possibility and instructed what to do if it does happen.

Estimated time to complete exercise – one hour