Scientific principle: crosslinking
Time required: 45 minutes plus 4 hours of setting time
Using the power of crosslinking, these realistic looking worms are not only amazing disgusting – they taste great too!
Equipment and ingredients
- 50 soft straws
- Elastic / rubber band (or length of rope to tie)
- High container
- 2 boxes of crystals or blocks of jelly / strawberry or raspberry jelly
- 10 g (1 tbsp) powdered gelatin
- 1/2 cup (125 ml) cream
- 375 ml (1 1/2 cups) boiling water
- Green food coloring
- Carefully pour the boiling water into a large jug and add the jelly / jelly and gelatin, stirring until dissolved.
- Add the cream and whip until well blended.
- Stir in 3 drops of green food coloring.
- Stretch the flexible part of the straws so that they are fully extended.
- Gather the straws 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 4 hours.
- If the straws start to float, put a weight on them to hold them in place.
- Once set, rinse the outside of the straws with lukewarm water to loosen the worms.
- Starting at the top, gently squeeze each straw with your fingers (or the back of a dull knife) and slide along the straw to push the worms onto a plate.
- To make the worms look like they are in the ground, crush the dark chocolate cookies and place them on the plate as a base for the worms to sit on.
The science behind edible worms
Jelly / jelly wobbles because it contains gelatin, a coiled protein chain that breaks down and floats like strands when hot water is added. As the water cools, the gelatin the strands twist and become entangled with each other, trapping the fluid they are in and transform the liquid into a solid structure. This process of gelatin strands tangling with each other is called crosslinking. Because worms have a high aspect ratio – which means they are long and thin – they need to be reinforced to help them maintain their shape. Addition of a surplus of gelatin causes more crosslinking, the chains making the structure firmer and more rigid when set. The jelly / jelly is usually transparent – or transparent – but the the protein and fat molecules in the cream deflect and scatter the light so that the worms become opaque. Mixing red jelly / jelly and green food coloring makes the worms “ realistic ” brown color – but you can, of course, give them any color you like.
What happens if you change the amount of gelatin in the worm mixture? why do you think it is?
»Are worms any different if you don’t add cream to the mix?
»What happens if you do not rinse the straws with lukewarm water before squeezing towards?
Why do you think hot water helps?
Scientific principle: chemical reactions
Time required: 20 minutes (plus 7 days)
Tie a knot with this fun experience and find out why calcium is so important for
Equipment and ingredients
- Glass jar with lid
- Chicken thigh bone
- The vinegar
- Rinse the bone under running water, scraping off any meat residue.
- Try to bend the bone holding it by both ends and notice how hard it is.
- Place the bone in the pot, cover with vinegar and seal the pot.
- Leave in the jar for 7 days.
- Remove the bone and rinse with water.
- Try to fold the boneagain and see how much easier it is than before.
The science behind the rubber bone
Bones are made up of a mixture of hard minerals and tough, flexible proteins like collagen. It is this combination that makes the bones not only strong, but also able to flex without overwhelming. Calcium is a mineral that helps give bone strength. This is why babies need lots of calcium-rich milk to strengthen their bones as they grow older. Vinegar is an acid liquid strong enough to dissolve calcium from the bone and make it less rigid. With more collagen than calcium, the bone goes from feeling hard and stiff to feeling rubbery. The relationship between structure and properties is very important to engineers and is indispensable in the design of structures that are both strong and light, just like bone.
»Does the experiment work with other acids – like lemon juice or sparkling soda?
»Do you think the size of the bone affects the time it takes for calcium to dissolve?
»Would dipping the bone in a liquid rich in calcium – like milk – make it stronger?
Scientific principle: surface tension Required time: 15 minutes
Watch how a beautiful and moving work of culinary art changes – before your eyes –
thanks to the power of the washing-up liquid which breaks the surface tension of the milk.
- Dishwashing liquid
- Liquid food coloring (two or more different colors)
- Pour enough milk on the plate to cover the bottom.
- Gently add a few drops of food coloring to the surface of the milk.
- Repeat using different colors, creating a polka dot effect on the surface of the milk. Notice how the food coloring floats.
- Dip a cotton swab in the dish soap, then hold it in the center of the plate, keeping it as still as possible.
- Watch the food coloring swirl around, creating art in motion.
- Dip the cotton swab in the dish soap again and touch it to another area of the plate.
- Repeat until the colors stop swirling.
The science behind colored milk
Milk is mostly water, but it also contains protein and fat. Because the oil and the water does not mix, the fat is stored as tiny droplets that float in the milk. The poured milk maintains itself on the plate using a property called surface tension, which is where the cohesive or sticky forces of milk molecules stick together. When drops of food coloring are added to milk, they may float to the surface rather than sink to the bottom. This is because food coloring is less dense than milk.
Dishwashing liquid, designed to break up grease and grease on dishes for cleaning, can also break down the fat molecules in milk. Dishwashing liquid breaks the surface tension. The tension on the surface pulls the surface of the milk away from the rupture caused by the soapy cotton swab – much like when a balloon bursts. As the food coloring floats above the milk, it moves with the surface, floating away from the drop of soap and allowing the flow paths in the milk to see. When the soap mixes evenly with the milk, the flow slows down – but just add another drop of soap to start the process again.
»What happens if you use other dairy products, such as cream, with more fat?
»Is the flow pattern the same if you use two drops of dish soap in place on milk?
»Does the temperature of the milk affect the flow and if so why?
Recipes from The Kitchen Science cookbook by Dr. Michelle Dickinson. The Kitchen Science cookbook is packed with fun “recipes”, each teaching an important science principle in a perfect format for parents and kids to enjoy together. Available on Amazon.?
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