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chapter 17 - Coggle Diagram

- - - - radiators
        
        keep rooms warm during the winter. Radiators have to quickly conduct heat away from the heat source before they can warm the air around them. Hence, they are made of metal.
      - cooking utensils
        
        conduct heat quickly from fire to food or water in them.
      - minor's safety lamp
        
        made of metal. The metal gauze conducts heat away quickly from a naked flame inside it, so that flammable gases outside never get hot enough to catch fire
      - boilers
        
        made of metal and conducts heat quickly from the heat source to the water, which is converted to steam.
    - - walls of buildings are made of bricks and other insulating materials. In warm climate, the insulating materials help to reduce heat gain by conduction. In very cold climates, the insulating materials also help to reduce heat loss by conduction.
      - handles of cooking utensils do not conduct heat easily. This allows a person to hold the utensils comfortably while cooking.
  - - - when rice is boiled in water
        
        rice grains placed into a pot of water.. As the water is heated, it expands and becomes less dense. This causes the rice grains to rise towards the surface of the water. The cooler water at the surface is denser and sinks with the rice grains.
    - - in coal mines
        
        in the past, coal mines were ventilated by vertical shifts sunk into the mines. These were joined by horizontal passages. A fire is lit at the bottom of one shaft. This cause hot, less dense air to rise from the shaft and cold, denser air to enter the other shafts.
    - - electric kettle : the heating coil of an electric kettle is place near the base of the kettle. This makes boiling more efficient as water becomes less dense and rises when it heated. This allows convection currents to be set up easily during heating
      - land and sea breezes : the land absorbs the heat from the sun and warms up faster than the sea. The air above the land is heated up and rises. Cooler, denser air above the sea moves in to replace the warm air above the land.
  - - - nature of the surface of the body (whether it is black or white or coloured, rough or smooth or shiny)
        The darker and rougher the surface, the higher the rate of radiation or absorption.
      - total surface area of the body
        the greater the area, the higher the rate of radiation or absorption
    - - good
        
        the heating surfaces of electric stoves are black, and the heating coil has a large surface area
        
        the backs of refrigerators have hot pipes is a good radiator of heat. This helps the pipes to lose heat quickly to the surroundings.
        
        the black pipes on solar water heaters are good absorbers of radiation from the sun. The water flowing in the pipes hence heat up more quickly.
      - poor
        
        a house painted in light colours to keep it cool on a hot day. The bright surface of the house absorbs less heat radiation than a dark surface
        
        light-coloured clothes are worn on hot, sunny days to keep us cool. The bright surface of the clothes is a poor absorber of heat radiation from the sun. This helps to keep us cool.
        
        the brightly polished surfaces of cooking utensils, teapots and kettles are poor radiators of heat. This keeps their contents hot.