First science experiment with my son.

I want to foster scientific thinking and curiosity in my son. The first grade science topic was different states of matter (gas, liquid and solid). Like many 1st graders, my son thinks he knows everything about it already. So I asked him some questions about evaporation and water vapor. His answers were very good.  My final question was "what would happen to the water in an airtight jar?" I don't remember his exact answer, but I remember responding.. "so.. that's your hypothesis?" He replied, "Yes!"...

And that is how we kicked off our first science experiment. I found two identical glass jars, one closed and one open. We filled it with filtered water and use tape and marker to indicate the start date. The experiment got off with a very slow start. I thought there would be some evaporation indoors. Nothing happened after a few days so we moved the experiment to a sunny spot outdoor. 

Son photographed experiment result after 1 week

My son was very excited when he saw the result 1 week later. He carefully marked the second measurement and saw that the open jar had about .25 inch less water. More importantly, he noticed another key difference between the two jars. There are water droplets accumulated inside of the top portion of the closed glass jar. He described it as 'I could see that water had nowhere to go'. To him, it is the key proof that evaporation occurred and water vapor was trapped.

The experiment was a big success for him. It validated his hypothesis. It was an even bigger success for me. We immediately hit the library and borrowed books for more science experiments. Our next 3 experiments are in the works:

1. Test the effect of salt in the water on evaporation
2. Test the effect of different size of hole on evaporation by using saran wrap
3. Make sugar crystals by evaporation of a super saturated sugar water mix