Monday, December 22, 2008
Wednesday, December 17, 2008
In the “Ball & Ring” demo, we heated a brass ball in the Bunsen burner and then tried to put the ball through the brass ring. It wouldn’t go through because it had expanded. We then plunged the ball into cold water and then tried to put the ball through the ring, and, it did! The ball had contracted when thermal (heat) energy, was taken away.
To show that liquids expand when heated and contract when cooled, we did the “Mood Ball” activity. Working with their partner, the students put the “Mood Ball” into hot water and observed the level of the water in the tube go up, or expand. Next, they placed the “Mood Ball” into ice water and observed the level of water in the tube go down, or contract. The students discussed how this activity was similar to how an alcohol thermometer works.
In the “Flask With A Balloon” demo, we put a balloon on a flask and then put the flask on a hot plate. After a while, the balloon began to “grow”, or expand. We then placed the flask on the window sill to cool and after a while, we saw that the balloon had “shrunk”, or contracted back to its original size.
Matter expands when heated and contracts when cooled. The volume increases when heated and decreases when cooled.
Monday, December 15, 2008
The Sharp-shinned hawk is a small hawk with a long, barred tail that ends with a square tip. Its wings are short and rounded. The adults have a blue-gray back and wings with reddish barring on their underparts.
The female Sharp-shinned hawk is about the size of a Blue Jay or a Mourning Dove, with the female bigger than the male.
Sightings of Sharp-shinned hawks in our area have dropped over the past 10 years. We are now seeing more Cooper's Hawks at feeders. It can be a challenge to tell the two species apart.