Tuesday, May 8, 2012

Science Week; Day 2

Today we worked on the following experiments;

"Ice Cube"

You will need
  • an ice cube
  • paper towel
  • a piece of string
  • salt

Place the ice cube on a paper towel and your piece of string across it. Make sure there is equal string on both sides. Now sprinkle the salt over the string where it touches the ice.

Wait a few minutes and then you should be able to lift the ice cube holding each side of the string only.

When you sprinkle salt on to the ice cube the salt molecules dissolve and join the water molecules thus changing the water’s rate of freezing. The rate of melting is now much faster than freezing hence causing the ice to melt. However, to be able to restore equilibrium, the water’s freezing point drops causing the ice to freeze out of the salt water. The salt starts to crystallize and ice refreezes around the string. This causes the ice cube to stick to the ends of the thread enabling you to pick it up just by lifting the string!

Sadly neither girl  could get this to work. It was a good opportunity to discuss why. We think we may have used too much salt which formed a barrier between the string and ice cube.

One of the experiments in the Brownie book was to make "Hokey Pokey" (honeycomb) which worked out well as Tuesdays are our home economics / baking days. Nothing like doing two subjects at a time!

We grabbed a random recipe off the internet and made some Hokey Pokey. Both girls were fascinated to see it "sizzle" (Agent Smelly's description).

I explained that the acid in the baking soda reacted with the liquid which causes gases which made the bubbles and the item to fizz. I really don't think they cared ... there was hokey pokey to be eaten!

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