Kiddipedia
Halloween is that time of year when sweet treats and ghoulish designs are everywhere. Why not embrace this time as a chance to also learn some science with this disgusting looking recipe from the Kitchen Science Cookbook. Designed to help you and your children to learn about scientific concepts including crosslinking, solidification, transparency and opacity this experiment is both fun and delicious. You can use sugar free jelly if you are watching your families sugar intake, or go all out on a bed of crushed chocolate cookies if you aren’t! You also can remove the cream if you have a dairy intolerance. Reusable silicone straws which are available in most supermarkets seem to work the best, but standard plastic straws will work too. Try to make these the day before you need them as a full night in the fridge to set will ensure the early bird catches the perfect worm.
Scientific Principle: Crosslinking
Time required: 45 minutes plus 4 hours setting time
Introduction
Using the power of crosslinking, these realistic looking worms not only look amazingly disgusting – they also taste great!
Equipment & Ingredients
- 50 bendy straws
- Elastic / rubber band (or length of string for tying)
- Jug
- Tall container
- Plate
- 2 boxes jelly/jello strawberry or raspberry crystals or blocks
- 10g (1 Tbsp) powdered gelatin
- 125ml (1/2 cup) cream
- 375ml (1 1/2 cups) boiling water
- Green food colouring
Instructions
- Carefully pour the boiling water into a large jug and add the jelly/jello and the gelatin, stirring until dissolved.
- Add the cream and whisk until fully mixed.
- Stir in 3 drops of green food colouring.
- Stretch the flexible part of the straws out so that they are fully extended.
- Gather the straws together and use a rubber band or string to hold them together.
- Place the straws upright in a tall, tight fitting container or jar.
- Carefully pour the mixture over the top of the straws, filling each straw. Refrigerate for https://nanogirllabs.com 4 hours.
- If the straws start to float, place a weight on top to hold them down.
- Once set, rinse the outside of the straws in lukewarm water to loosen the worms.
- Starting at the top, gently squeeze each straw together with your fingers (or the back of a blunt knife) and slide down the length of the straw to push the worms out onto a plate.
- To make the worms look as though they are in soil, crush dark chocolate cookies and lay them on the plate as a base for the worms to sit on.
The Science Behind Edible Worms
Jelly/jello wobbles because it contains gelatin, a coiled up protein chain that unravels and floats around as strands when hot water is added. As the water cools down, the gelatin strands coil back up and become tangled with each other, trapping the fluid they are in and transforming the liquid into a solid structure. This process of gelatin strands becoming tangled with each other is called crosslinking. Because the worms have a high aspect ratio – meaning they are long and thin – they need to be stiffened to help them keep their shape. Adding the extra gelatin causes more crosslinking to occur, with the chains making the structure firmer and stiffer when set. Jelly/jello is usually transparent – or see through – but the additional protein and fat molecules from the cream deflect and scatter the light so that the worms become opaque. Mixing red jelly/jello and green food colouring makes the worms a ‘realistic’ brown colour – but you can, of course, make them any colour you like.
Explore further
What happens if you change the amount of gelatin in the worm mixture? Why do you think this is?
- Do the worms look different if you do not add cream to the mixture?
- What happens if you do not rinse the straws in warm water before squeezing out the worms?
- Why do you think the warm water helps?
