Before the session connect to the website apricot.ap.polyu.edu.hk ready for the computer simulation in Activity 8.
The simulation shows fractals growing and has the options - Grow, Pause, Resume, Reset and Grow slowly. Practice before the session. It helps to start by showing the fractal growing slowly at first so the children see the particles adding slowly. Then explain that a snowflake has many, many more particles and show the quicker rate of growth. Stop it a few times to discuss whether there is sufficient detail for the structure to look like a snowflake.
- 2 empty spray bottles of the sort for cleaning materials – well washed out.
- Half fill with water
- Bubble pack or other heat insulation material
Unscrew the top of one and squeeze some air out. Tighten the top and place the bottle in a freezer. Before the presentation, remove the bottle of ice from the freezer and insulate it with several layers of bubble pack or other good heat insulator to prevent the ice melting before the presentation.
Optional items to help to explain melting:
- Melted candle
- Soft chocolate
- Piece of pumice stone
Other items to help later explanations if available:
- Two transparent tumblers One containing water which is melted ice and one containing tap water.
Activities 12 and 13
- Overhead projector (OHP)
- 3 narrow strips of paper (about 15 cm x 0.3 cm)
- Discs to represent atoms - These could be washers about 1cm in diameter or transparent discs, pennies, ‘tiddlywinks’, buttons etc
- They must all be the same size.
- Washers or transparent discs allow the strips of paper to be seen clearly during the demonstration on the OHP
- Pennies are easily obtained for class use.
Linked class activity
- Small bags containing about 12 discs – one bag per group of children
- 3 thin strips of paper or coloured plastic per group
- Bubble rafts
- Washing up liquid
- Yogurt pots – 1 per group of children
- Large bowl – 1 per group of children (eg. washing up bowls, large ice-cream tubs (at least 3 litres), etc )
Before the session make a small pin hole in the centre of the base of each yogurt pot. (Note: the hole should be made in advance because it is difficult to push the pin through. The hole should be as small as possible so that the bubbles are small. )
The detergent must be added very slowly to the water (NOT the water to the detergent) so no bubbles are formed. It is best to do this in advance and hand the bowls round at the appropriate time.
The water must be deep enough for the base of the up-turned yogurt pot to be below the surface of the water. If shallow containers are used then a small fromage-fraise pot is better.
Once the air trapped air has left the yogurt pot, a child can lift it carefully and put it back in the water to form more bubbles from the trapped air.The children should guide the bubbles with their hands so they see them form a single layer and move to become close packed (anneal).