8/28/09
Post date: Aug 28, 2009 10:33:20 AM
Bell Activity: What determines whether something will sink or float?
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
Page 58: 1-7 due Monday