1. Interactions of water and Energy

2. Questions: On cool fall mornings when you drive passed the harbour, you sometimes will see steam rising off the water. On cool fall mornings when you drive passed the harbour, you sometimes will see steam rising off the water. Why? Why? Does water or air cool down faster? Different substances change temperature at different rates Why?

3. Earth Only 30% of the earth’s surface is land Only 30% of the earth’s surface is land Therefore most of the incoming solar radiation that gets past the atmosphere hits water Therefore most of the incoming solar radiation that gets past the atmosphere hits water The interactions between this solar energy and water are very important to life on earth The interactions between this solar energy and water are very important to life on earth

4. Interactions between energy and water: The type of interaction depends on the state of the water (s, l, g) The type of interaction depends on the state of the water (s, l, g) For example: For example: fresh white snow reflects 90% of radiation ice reflects 50% of radiation water reflects only 7%

5. Specific Heat Capacity The amount of heat needed to change the temperature by 1°C for 1g of substance. The amount of heat needed to change the temperature by 1°C for 1g of substance. Each substance has a unique specific heat capacity. Each substance has a unique specific heat capacity. Substances.h.capacity (J/g °C) Fresh water 4.18 Ocean water 3.89 Air1.00

6. Specific heat capacity of water: Water has a relatively large spec. heat capacity Water has a relatively large spec. heat capacity A larger specific heat capacity results in a smaller temperature increase A larger specific heat capacity results in a smaller temperature increase This helps to moderate water’s temperature because water can absorb a large amount of energy with only a small temperature change This helps to moderate water’s temperature because water can absorb a large amount of energy with only a small temperature change

7. Moisture in the Air Cold air can hold less moisture then warm air Cold air can hold less moisture then warm air Therefore when the air temperature is high, the amount of water vapour can be high Therefore when the air temperature is high, the amount of water vapour can be high Moist air takes a bit longer to cool then warm air Moist air takes a bit longer to cool then warm air

8. Saturation When there is as much water vapour in the air as possible at any given temperature, we say the air is saturated When there is as much water vapour in the air as possible at any given temperature, we say the air is saturated

9. What happens in the summer when you bring a cold drink outside? Lets say the air temperature is 26 degrees Celsius. When the air is this warm it can hold a lot of water vapour Lets say the air temperature is 26 degrees Celsius. When the air is this warm it can hold a lot of water vapour When you bring out the cold glass, the air directly next to the class becomes colder. When you bring out the cold glass, the air directly next to the class becomes colder. This colder air can not hold as much water vapour as the warmer air, so the water “falls out” This colder air can not hold as much water vapour as the warmer air, so the water “falls out” It “falls” onto the glass because that is a surface for the water droplets to form on It “falls” onto the glass because that is a surface for the water droplets to form on

10. Read pages 431-432 Think about it and answer the questions on the sheet Think about it and answer the questions on the sheet

11. Q=mc ∆ T Q = energy absorbed (J) Q = energy absorbed (J) m = mass of substance (g) m = mass of substance (g) c = specific heat capacity of substance (J/g) c = specific heat capacity of substance (J/g) ∆ T = change in temperature (°C) ∆ T = change in temperature (°C)

12. Practice: 1. What is the Q, if 5.2kg sample of limestone has a change in temp. of 16.3 °C? 2. What is the change in temp, if a 9.2g sample of mud absorbs 950J of energy? 3. An unknown sample absorbs 6000J and has a temp change of 62 °C. It has a mass of 2.6kg, what is the specific heat capacity?

13. Heat of vaporization Heat of vaporization  liquid to gas requires energy  gas to liquid releases energy Heat of fusion Heat of fusion  solid to liquid requires energy  liquid to solid releases energy

14. Changes in state of water sheet

15. Sample problem 1. What is the heat absorbed (Q) if 2.0g water is heated from 10°C to 25°C ? Q=mc ∆ T Q=mc ∆ T =2.0g x 4.18 J/g °C x (25 – 10 °C) =125.4 J Remember J = joules, the unit for energy