Steam Sterilizer To Teach The Water Cycle
It is always fun to use ordinary objects to learn science. It is a great learning experience because when you learn by associating something with a principle, you tend to remember easily. I am a hands on learner and we love to play with ideas around here. (Please note: For your convenience, some of the links in this post contain affiliate links. If you make a purchase through them, we may make a small commission with no extra cost to you. Thank you for supporting this blog!)
The age old experiment of teaching the water cycle by boiling water and cooling it in the fridge is too boring. Come on tell me, even you think there is nothing exciting about it! We found our little experiment while my son and I chatted over a little quality time… in the kitchen. I was doing the dishes. He was sitting at the kitchen counter telling me about his day. The baby’s bottles were being sterilized in our six minute Steam Sterilizer
A Steam Sterilizer
The steam steriliser consists of a metal plate over which water is heated. There are two holed compartments placed over it, one over the other.
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The lid has a vent. When the sterilizer is turned on, the water begins to boil. Since there is only a little bit of water there, the boiling water turns to steam and as the temperature rises, so does the steam. It passes through the holes in the compartment and since the lid is closed, there is a little pressure building up.
How Sterilization works:
The principal of steam sterilization is that water boils when its vapour pressure equals that of the surrounding atmosphere. Since the steriliser is a closed compartment, when the pressure inside the vessel increases, the temperature at which water boils also increases. A temperature of 80 degrees for 5-10 minutes is enough to kill the vegetative forms of all bacteria, yeasts and moulds. When this vapour (steam) comes in contact with a cooler surface (the bottles), it condenses to water and gives off its (latent) heat to that surface. This goes on… steam touching cooler surface to become water and everything inside heating up. This moist heat is what kills those germs inside.
How the Sterilizer works:
When the sterilizer is turned on, it starts to boil water. Steam rises quickly. After 6 minutes of heating, the steriliser shuts down. That means, there will not be any more heating of water. The steam that is in there gets out from the vent and it is now safe to open it.
How the Water Cycle Works:
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| photo credit: Global Water Partnership – a water secure world via photopin cc |
The water from the sea is heated up by the sun. The water vapour rises up into the sky. They move with the air till they collect together and get cooled enough to fall to earth as rain.
How can you use a Steam Sterilizer to teach the water cycle?
The water on the heating plate is heated up. It rises through the chambers towards the cooler top.
As long as the steriliser is working, steam will keep rising. Once it is off, the excess steam is removed from the vent but that which is collecting in the bottles, it is still trapped.
When we lift the lid off the steriliser, the cool air passes in and cools the surface of the bottles from outside.
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| When we lift the lid |
The vapour inside turns to water. You can see the water trickling down the sides. In other words, rain.
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| RAIN!! |
My son had watched as I placed the bottles in the compartments, poured a glass of water in the pan and stacked those compartments again. He saw me plug it in and I asked if he wanted to switch it on. He did. We patiently watched as the sterilizer started boiling the water and the zhhhh sound the machine working. We saw the steam on the walls of the transparent upper compartment. The steam started to escape after a while and then the whole thing shut down. We removed the lid and saw the caps and teats that were still hot with the steam. We saw the water condensing on them. Next we removed the upper part for the bottles. Yep, there was RAIN!
He saw the hot water and steamy bottles. I turned one over and tilted the lid of the sterlizer. The rush of cool air condensed the steam and he saw droplets inside the water. He was so excited to see rain!
We talked about the water cycle a little more. He was one happy little boy!
Teaching science at home is fun. It doesn’t always have to be a big experiment. Sometimes just involving them and teaching them through ordinary things and explaining the principle behind them works. Oh.. by the way… that was two lesson in one : water cycle and sterilization!
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This is the steam Sterilizer that we use and have trusted with our four little ones! 🙂
