School science visit

Today was my visit to the primary school where I talk to the kids about science stuff. I had three separate session with kindergarten, Year 1, and Year 2. As mentioned on Saturday, I presented a talk on dinosaurs for the K and 1 kids. I included a bunch of photos of fossils with feathers, and showed them what feathered dinosaurs look like. The conclusion was that only some of the dinosaurs died out a long time ago, but some of them – the birds – never died out at all, and are still around us today. They really enjoyed it, so that was good.

With the Year 2 class I did a general Q&A. Some of the questions they asked included:

  • Where did the Earth’s water come from?
  • Why did the dinosaurs die out?
  • Where did humans come from?
  • Why isn’t Pluto a planet any more?
  • How do you make a black hole?
  • Does the Earth run on coal? – I talked a bit about what coal is, and how it’s used to make electricity, and how it adds carbon dioxide to the atmosphere, and how this is a bad thing because it’s causing climate change, but how hard it is to stop using it because people need the electricity.
  • How do potions work? – This was fun. I talked a little bit about how potions are fictional and don’t really work like in books and movies, and also a bit about alchemy and how alchemists used to believe they could make magical potions. By mixing things together and learning how they worked, they actually invented the science of chemistry instead.

Besides these three large groups, I also had Science Club with the group of 13 students I’ve been working with all year. It’s really quite a strange thing to be left in charge of 13 kids aged 7 to 10, with no other supervision, and be allowed to do science experiments with them (not on them!). Today I brewed up a pH indicator liquid by mixing hot water and shredded red cabbage. Within half an hour (during which I went over the results of our previous laser experiment), we had a rich purple liquid strained off. I gave each child a plastic cup and one of the chemicals I’d brought in. Then we added the cabbage liquid to each and watched them change colours:

pH experiment

pH experiment

From left to right around the table, the kids had: baking soda, soda water, white wine, bleach, apple juice, cream of tartar, lemonade (i.e. Sprite/7-Up for the Americans), vinegar, lemon juice, and ammonia solution. The bleach and ammonia I gave to the oldest kids, and made them wear rubber gloves for safety. And you can see the different colours they produced. Here’s a shot with them arranged in order of pH:

pH experiment

After establishing a sequence of colours for the chemicals, we tried mixing some of them. Adding baking soda to the vinegar made it (1) fizz up, (2) change colour, becoming a deep blue-purple. We mixed a few other things together, and the kids tried to predict the resulting colours (without much success). We established that mixing acids and bases tends to neutralise the result, making it closer to the original neutral purple colour. I made absolutely sure we didn’t mix the ammonia and bleach – I didn’t want to be generating chlorine gas!

This pretty much took up my whole day, as it took a while to drive home in the late afternoon traffic. And I was exhausted! I don’t know how school teachers do this every single day!

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