11/14/08
Post date: Nov 14, 2008 1:5:56 AM
Bell Activity: Continue working on your labs from yesterday. If you finished yesterday, calculate the thickness of a piece of aluminum foil using the fact that aluminum has a density of 2.7 g/mL. Assume the aluminum foil is in the shape of a very thin box.
Will it float?
Density determines whether something will float in water or not.
Anything with a density greater than water's (1 g/mL) will sink, anything with a density less than that will float.
Examples from lab - will they float?
Test in aquarium
Aluminum foil has a density of 2.7 g/mL -- will it float? Can you form it into a shape that floats?
Large boats float, despite the fact that the metal they are made of is much more dense than the water, because their shape makes their volume much larger and include a lot of air.
Humans vary their densities by breathing
With lungs full of air, our density is less than 1 and we float easily in water.
With empty lungs, our density is more than 1 and we sink in water.
Saturn
m = 5.68 x 10^29 g.
V = 8.23 x 10^29 mL
D = 0.69 g/mL --- less than water! If we could find a big enough aquarium and dropped Saturn in it, it would float!
Page 54: 1-3 due Monday
Chemical properties
Describe how a substance changes into a new substance, either by combining with other elements or by breaking apart into new substances
Examples
Flammability - does something burn?
Reactivity - how easily does something react with other matter?
Iron reacts with oxygen to make rust
Flour, water, and yeast react to make bread when heated