COLOUR CHANGING MILK


Some very unusual things happen when you mix a little milk, food colouring, and a drop of washing up liquid. Use this experiment to uncover the scientific secrets of


soap. Prep time: 5 mins Experiment time: 2 mins


You will need: ✔ Whole Milk ✔ 2 paper plates ✔ Red, yellow, green and blue food colouring ✔ Washing up liquid ✔ Cotton buds


Make a dancing rainbow in your milk!


✔ Pour enough milk in the dinner plate to com- pletely cover the bottom and allow it to settle.


✔ Add one drop of each of the four food colours to the milk. Keep the drops close together in the centre of the plate of milk.


✔ Place a drop of washing up liquid on the tip of the cotton bud. Place the soapy end of the cotton bud in the middle of the milk and hold it there for 10 to 15 seconds. Look at that burst of colour!


✔ Add another drop of soap to the tip of the cotton bud and try it again. Experiment with placing the cotton swab at different places in the milk.


✔ Repeat the experiment using water in place of milk. Will you get the same eruption of colour? If not, why not?


Why does this happen? Milk is a solution that is made up of water, vitamins, minerals, proteins, and droplets of fat. Fats and proteins are sensitive to changes in the surrounding solution (the milk). When you add soap, the weak chemical bonds that hold together the proteins and fat in the milk solution are changed. The molecules of protein and fat bend, roll, twist, and contort in all directions. The food colour molecules are bumped and shoved everywhere, providing an easy way to observe all the invisible activity. At the same time, soap molecules combine to form groups of soap molecules. The soap molecule groups mix with the fat in the milk causing the milk fat and dish soap to swirl and churn. Once the soap molecule groups and milk fat are evenly distributed throughout the milk, the motion stops.


12 WWW.MUMSMAG.NET What you do:


✔ Make sure that the bottle-top is open. Make a ring using the Blu-tack and use it to make an airtight join between the bottle-top and the CD (keep the shiny side facing down). You could glue the bottle–top if you prefer.


✔ Put the CD hovercraft onto a large, smooth surface.


✔ Blow up a balloon and pinch the end so that the air doesn’t come out.


✔ Stretch the balloon’s opening over the bottle-top.


✔ Now let go of the balloon and give your hovercraft a gentle nudge.


You could try:


Try using different materials to make your hovercraft. What happens if you try it on different surfaces? What about using different- sized balloons?


Why does this happen?


When air escapes from the balloon, it lifts the CD and creates a cushion between the CD and the table top. The CD floats on a cushion of air. Gently push the CD and it will move along very easily, which does not happen if there is no air cushion. This is because there is no resistance due to friction between the CD and the table top. This could lead to a discussion about other ways in which friction can be reduced, for example, by having very smooth surfaces or using lubricants.


HOVER BALLOON


Make a balloon- driven hovercraft


You will need:


✔ CD (it might get ruined, so don’t use your favourite!)


✔ bottle–top with a push/pull closure – like those on some sports drinks or water bottles


✔ Blu-tack or glue ✔ balloon


How to make BATH BOMBS


You will need: ✔ A large mixing bowl


✔ Moulds to shape the bath bombs (we used silicon strawberry-shaped ice-cube moulds)


✔ Kitchen scales ✔ A spray bottle of cold tapwater or witch hazel ✔ 75g Bicarbonate of Soda ✔ 13g Powdered Citric Acid


✔ 5 drops Essential Oil of your choice (laven- der is soothing and helps kids get to sleep!)


✔ Several drops of food colouring of your choice (we chose red)


What to do:


✔ Mix the bicarbonate of soda and citric acid together in a large bowl


✔ Mix in essential oils or fragrance


✔ Quickly, but carefully, add the drops of food colouring to desired shade


✔ Gradually spray the mix with water bottle to make a consistency that will hold its shape when you squeeze it.


✔ Be careful not to use too much water, as the bath bombs will start fizzing too soon!


✔ Add the mix to the mould and gently press down, taking care not to leave any gaps. At this point you can join two moulds together to make a 3D shape.


✔ Leave to air dry naturally; place near a radia- tor or airing cupboard.


✔ If you’re feeling creative, you can also add these to the dry mix: dried flowers or fresh petals (rose or lavender are good) carrier oils to soften skin (e.g. almond or jojoba oils) glitter (edible glitter is available in the supermarket baking section) Please remember the ‘added extras’ take extra effort to clean off the bath afterwards!


The science bit... When water is added, there is a chemical reac- tion with the sodium bicarbonate and citric acid which forms carbon dioxide gas, which produces the bubbles, making it fizz. For an excellent detailed description of how to make bath bombs in quantity with several children for school fairs, etc. take a look here: timetocraft.co.uk/?p=5807


THE BIG BOOK OF SCIENCE THINGS TO MAKE AND DO


Usbourne Publishing have offered a Mums’ Survival Guide reader the chance to win this superb Big Book of Science Things to Make and Do. It’s packed full of stickers and exciting crafty science projects to appeal to boys and girls of all ages.


Simply email your name, address, and ages of your children to sciencecomp@lincolnbrody.co.uk


The winner will be the first name drawn at random. Only one entry per household. For competition terms and conditions please visit www.lincolnbrody.co.uk/competitions. Closing date for entries is 29/04/2013.


Survival Education


WIN:


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