heat

1. heat

2. Heat and the water cycle

3. Heat and the water cycle • The Sun – provides radiant energy to warm the air and water • Vaporization (Evaporation) – liquid water changes state as it absorbs heat (warm air containing moisture rises) • Transpiration – plants release water as vapour • Condensation – moisture in cooling air condenses around dust particles forming clouds • Precipitation – water falls back to earth as a liquid in warmer air (rain) or solid in colder air (hail/sleet/snow) • Surface Run Off - water returns to larger bodies (streams, lakes, oceans, seas) • Groundwater – plants absorb water through soil

4. HEATing homes Heating a Single Room: • Air = good heat insulator = poor heat conductor • To heat air in a room, a convection current is needed ex) Using an electric heater

5. HEATing homes Hot Water Heating Systems: • Some homes and buildings use hot water to provide heat ex) radiator system

6. Wasting heat

7. HEATing homes Forced Air Heating Systems: • In forced air heating systems, air is heated in a furnace and then driven by a fan through ducts to the rooms

8. HEAT CAPAcities • Different substances heat up (or cool down) at different rates • The heat capacity of a substance = a measure of the amount of heat needed to raise the temperature of the substance = a measure of how much heat the substance releases as it cools

9. HEAT CAPAcities Heat Capacity and Climate: • Why are Regina, Winnipeg, and Quebec City so cold? • What makes Victoria, Toronto, and Halifax warmer in winter? Heat Capacity and Solar Heating: • How can the Sun’s radiant energy and knowledge of heat capacities help to design a solar heated home? • Consider how water and concrete absorb radiant energy

10. producing heat Energy sources can be grouped as… • Renewable = not destroyed in the process of being used ex) solar energy, electricity produced from moving water • Non-renewable = gradually used up or may run out entirely ex) coal, oil Four Ways of Producing Heat: • Mechanical Energy - (changes into heat and sound) Note: • A mechanical force = a force caused by objects in contact with each other

11. producing heat a) Friction - an example of a mechanical force occurring between objects in motion that are touching (between solids, or between a solid and a fluid) b) Distortion - occurs in objects that are stretched or forced to move back and forth

12. Producing heat c) Percussion - occurs when objects are pounded d) Compression - occurs when, air for example, is forced into less space; often increases pressure

13. producing heat Four Ways of Producing Heat Continued… 2) Chemical Energy - stored in fuels such as oil, wood, coal, natural gas (changes into heat and light) 3) Electrical Energy - needs electricity to change to heat (→ heat and light) ex) in a stove, an electric current passes through an element made of a material that resists the flow of electricity. The resistance causes the element to heat up. The greater the current, the hotter the element becomes (red – stove, white – light bulb)

14. producing heat Four Ways of Producing Heat Continued… 4) Nuclear Energy - energy stored in the nucleus of atoms - energy can be changed into other forms of energy, such as heat, via different processes → Nuclear Fusion – nuclei join and some mass changes into energy ex) the Sun → Nuclear Fission – nuclei split and some mass changes into energy ex) uranium Ex) Nuclear stations: nuclear energy → heat (to heat water) → mechanical energy (spinning turbine) → electrical energy + heat

15. Solar heating • There are two basic ways of using solar energy to provide heat 1) Passive Solar Heating: - the system lets the solar energy in and prevents much heat from getting out - is not expensive and is easy to maintain ex) most homes use passive solar heating simply by allowing sunlight to shine in the windows Ex) Greenhouse Effect: = the process of trapping radiant heat inside a structure

16. Solar heating ex) Greenhouse Effect = the process of trapping radiant heat inside a structure

17. Solar heating 2) Active Solar Heating: - the system absorbs as much solar energy as possible and distributes it throughout the building - usually requires another source of energy besides the Sun, at least as a backup during times of little sunshine