Sunday, 7 April 2013

Learning About the Water Cycle and Water Filtration

We started out by reading the book 'A Drop in the Ocean, the story of water' and then demonstrated a couple of the rain cycle processes to illustrate what happens.
The set-up above is very simple and examples can be found all over the net so I have not attributed it to any one source. It consists of having warm water in a jar/jug, and placing a plate/bowl of ice cubes at the top, then waiting a little. What you see happening is water vapour that has evaporated from the warm water condenses onto the cooler sides of the jug and then runs down the sides into the water at the bottom (this represents precipitation!). I found a cool idea on the net for making this in a ziploc bag with the cycle drawn on the bag with permanent marker pen
Next we made clouds in a bottle using instructions from this great website and the children were amazed by this. You have to roll the bottle between every try to get rid of the condensation and look carefully as you release your grip on the bottle. What you see is a faint cloud very definitely forming as the pressure drops inside the bottle. What a fantastic way of showing the conditions needed to form clouds!
Next we played a water cycle game, which was inspired by an idea I saw (and now can't find again) where bowls of different coloured beads were placed around the room and the children rolled a dice at each station to see where their water droplet went next. They wrote a story about their water droplet at the end. I thought it was a neat way of showing that the water cycle is more complex than simply cloud-rain-lake-evaporation-cloud. I thought about it but couldn't make it work for a group of three children so adapted it by making several sets of cards using clipart and laminating them before cutting them out and shuffling them. I drew a basic cloud line and ground line on a large A2 sized piece of paper and the children took turns choosing a card from the pile and placing it on the paper where they thought it went. As the game went along we added a house, rocks as we talked about groundwater, a well drawing on the groundwater, a drainage system, and lots of arrows showing the potential movements of water from one area of the board to another. I had considered that I was under prepared for this part of the session as I didn't have a pretty pre-drawn game board all well thought out in advance. As it happened it was the best way to do it as the children TOLD ME the links and showed me where the arrows should point as we went along and it was a really good learning exercise for them.
After all the cards were used up, we talked about groundwater some more and linked it to drinking water and what our water looked like from a tap and how we thought it ended up so clean. The children thought that the water from a well would be muddy and not safe to drink. We talked around that a little with me asking them what was the point of digging wells if the water was going to be dirty and undrinkable? I lead them on to thinking about the layers of the ground that the water went through before it was drawn up in a well. They identified plants roots, mud, sand and stones as possibilities. Then I introduced the bags of materials I had collected (sand, stones, mud and some cotton wool pads as a control.
The girls were eager to get stuck in and split the tasks up between themselves to set up the filtration stations. I had prepared a bottle of muddy mucky water full of bits and they shared it between the filters. We eagerly watched to see what would happen, the girls made predictions, one thought the sand would filter the water the best and another thought the stones would. Disappointingly all of the filters produced filtered water of the same colour......
....... so we brainstormed what might have happened - what was different between the filter stations? What was the same? They realised that each filter station also had a coffee filter in the bottom (to stop the materials falling out of the milk bottle lid hole), and wondered if that may be very good at filtering and be the reason why the water samples all looked the same was because the filters were there?
We had a quick think about the problem to be solved..... we needed something in the bottom to stop the materials falling through but not affect the water being filtered. I suggested the fruit nets that were in the bin from the shopping yesterday and off we went to reclaim them! They plugged the holes nicely and the girls carefully scooped out the materials from the coffee filters and put them inside the new filters. We made some more mucky water to filter and off we went again. This time the sand did produce the cleanest water, not completely clean but not bad and the girls noticed that the particles that came through sank to the bottom so Faith decided that she would try it and just be careful so she didn't drink the bits..... erm no, maybe not Faith but full points for bravely offering your services! I prompted the girls to look at the filters and see what had changed about them and what was the same, they noticed that the water had made holes in them and that the stones now had big pieces of muck in it, like grass and twigs.
Enthused by their success the girls wanted to try layering the materials to see if all of them together produced cleaner water than individually. They set this up independently but in the end it produced filthy water as there was a sudden 'whoosh' and the net plugging the pouring hole gave way under the weight, leaving a hole through the materials. The girls were intrigued by this hole...... and chatted about how and why the water had gone through in that particular place.

All in all, although I felt under-prepared, and hadn't thought through the effect that the coffee filters would have on the experiment, it was the perfect set-up as it posed natural problems for the girls to think about and solve. It high lighted the importance of the design of an experiment and the planning, and that a failure doesn't mean disaster, it means thinking and adapting and testing again. The experiment was flexible enough that the girls could take it in the direction that they were interested in so was great for allowing them to take the lead instead of being narrow and one-directional. The happy occurrence of a bit of water erosion on the combined filter at the end could lead nicely onto other topics! 

1 comment: