Tuesday, Oct 14, 2008 - Block 4B

Went over density graphs.

We use line graphs in science to find relationships between variables. In the round object lab, the slope gave the value of pi. In this lab, the slope gives the density. Density of water = 1 g/cc. Objects with a density greater than 1 will sink, and those with a density less than 1 will float.

The weight itself is not the deciding factor, it is the ratio of the mass to volume. A large object will have greater mass, and a smaller object will have less mass but the ratio, mass to volume is the same for the same substance.

Did Sink or Swim. The heavy bowling ball floated and the small piece of ironwood sank.

Students calculated their volume using their weight and a density of 1 g/cc. Related the volume to 2 liter bottles of soda and to the liter beaker and graduated cylinder.

We use graduated cylinders to accurately measure volumes of liquids. They are called graduated because of all the grades or markings. Graduated cylinders read in milliliters. 1 milliliter = 1/1000 liter = 1 cc

If you pour liquid in the graduated cylinder, it often does not lie flat, there is often a dip called the meniscus. This is caused because the water is more attracted to the glass than itself. To accurately read the volume, you need to look straight on and read at the bottom of the meniscus.

Gave students exercise sheet on reading volumes for various graduated cylinders. Went over the sheet in class.

Handed out rainbow lab. Gave students last half hour of class to work on it but many ran out of time. May need to redo it on Monday.