Water Pressure

I don't have a lot of pictures, but understanding water pressure is essential to understanding how dams and water towers and pipe systems work, so we had a lot of discussion about it (and, peripherally, air pressure). Along with the bottle demonstration pictured above, the older boys were delighted to play this trick on Sam. We also used Sebby's straws (he got these for his birthday a couple years ago) to experiment with the ways that pipe thickness, distance, gravity, etc. affect water pressure.

They took their hole-y water bottles outside and pretended they were water towers (enterprising Abe, whose bottle worked fastest, was charging "money" for the others to fill their cups at his water tower)

We talked about clouds and rain and lightning on one of the days (just briefly; we will do a longer unit on weather sometime because there's lots more to cover!), and made these clouds in a bottle. We also loved making "lightning" with balloons and light bulbs (as described here and here). We did this demonstration in my closet and the kids LOVED it. They were all giggly and nervous there in the dark at first, not knowing what would happen, but after we made it work a few times, they could hardly be persuaded to stop! [note: We used a CFL and I thought it looked much more impressive with that than with his long fluorescent bulb in that second link, but I do really like his explanation of volts vs. amps and how fluorescent bulbs work. ]

A couple other good resources we used on water and air pressure:

http://thehappyscientist.com/science-experiment/feeling-pressure

http://www.asme.org/kb/news---articles/articles/k-12-grade/5-ways-to-demonstrate-air-pressure-to-children

http://thehappyscientist.com/science-video/cartesian-diver

http://www.history.com/shows/underwater-universe/videos/the-science-of-water-pressure#the-science-of-water-pressure

http://www.abc.net.au/spark/experiments/s1199904.htm