Unit 13 The water planet教學設計
1. what are the properties of water?
water is polar.
water is liquid at room temperature.
water has a relatively high freezing point.
water has density 1,000 kg/m3.
water has high heat capacity. …
2. what causes water to have such unique properties?
－its molecule form / chemical structure.
3. what is water molecule like?
chemical structure: two hydrogen atoms and one oxygen atom.
different parts of it: a slightly positive end and a slightly negative end, so it is polar.
the function of it: it causes water to be able to dissolve both solids and gases, and that’s why water can break down nutrients quickly.
4. do pure water and salt water have the same chemical structure? does pure water have salinity?
qs: 1) what’s salinity?
2) what is sea / salt water? － a mixture of pure water, dissolved gases and solids.
3) how does salinity affect water?
4) how does it affect water’s weight and freezing point?
－ the higher salinity water has, the heavier the water is.
the higher salinity is, the lower the freezing point of water is.
5. salinity also has something to do with the density of water.
the higher salinity is, the higher density of water is.
qs: 1) what is density?
2) how is density measured?
3) which is denser, water or oil?
4) what will happen when water and oil are in the same container? what does this phenomenon illustrate?
－oil floats on water. a less dense substance floats on a denser substance.
5) does water in the same ocean have the same density?
－no. denser water sinks and pushes less dense water to the surface.
6. that’s why the ocean water will never stop moving. ocean motion
qs: 1) what does ocean motion mean?
2) how does ocean motion work?
－denser water sinks and pushes less dense water to the surface.
ocean motion helps move nutrients around and adds energy to the marine ecosystems.
3) what causes ocean motion?
－changes in salinity and temperature.
7. the temperature of the ocean water always keeps steady, making the ocean a safe and comfortable habitat. do you know why?
－water has a relatively high heat capacity.
qs: 1) what is heat capacity?
2) what’s the function of heat capacity?
－it determines how a substance absorbs and releases heat;