Praxis: The colours of the season
By Medicine Hat News on December 15, 2018.
I don’t know about your house, but mine is filled with quite a bit of excitement as the holiday season is fast approaching! This time of the year, it is never too early to start thinking about what we should be leaving Santa out on Christmas Eve — if you think about it; it really is our last chance for some of us to redeem ourselves (you know who I am talking about!). This week, I thought that we could show Santa himself a little magic science with some of that milk we all expect him to drink with the cookies. Let’s get started! *Remember to ask an adult before doing this experiment. Materials – pie tin – red food colouring – green food colouring – cotton swabs – liquid dish soap – plate – milk (homogenized is best) Procedure 1. You may want to gather two sets of materials so you can leave one out for Santa to do this experiment as well. 2. Place the empty pie tin on a flat surface to work. 3. Fill the pie tin approximately half full of milk. 4. Place a couple of drops of red food colouring at one end of the pie tin and place a couple of drops of green food colouring at the other end of the pie tin. 5. Dip the tip of the cotton swab in the liquid dish soap. 6. Take the cotton swab and dip it, soap side down near one of the drops of food colouring, pull it out quickly. 7. Observe what happens. What is going on? There should have been two reactions in this experiment. The first was the repelling of the milk away from the cotton swab soaked in liquid soap that you dipped into the milk. You should have seen this large circle of white growing. The second reaction was the beautiful colour swirling around in the milk. It may have only lasted a moment or two, but it looks like the milk and colours are dancing around. If you want to see it again, try a clean cotton swab with another dab of liquid dish soap. It will happen all over again and again and again. The science tells us that this is happening because the food colouring is water soluble and does not mix very well with the high fat content in the homogenized milk. The surface molecules in the milk will begin to pull on the puddles of colour. They will slowly begin to spread in all directions. By adding the liquid soap, you are weakening the pull of the water molecules in the centre, causing the stronger water molecules on the outside of the container to pull the puddles of colour toward them. The soap also breaks down the fat molecules allowing the food colouring and milk to mix. Patty Rooks is senior scientific consultant at PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. 23-22
