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effects of heat and its transmission (how does radiation occur (what…

- - - - at room temperature, metal bar fits into gauge . when bar is heated, it expands so it will not fit in the gauge. as it cools down again to room temperature, it contracts and will then fit into gauge
    - - test tube of colored water is dipped into beaker of hot water, as water warms up, it expands and rises up this glass tube. when test tube is placed in ice cold water, water cools and contracts, causing level of water in thin glass tube to fall
    - - warm test tube of air by wrapping hands around it. air expands, causing drop of colored water in glass tube to rise. when test tube is placed in ice cold water, air contracts, causing drop of colored water to fall
      - expand much more than solids and liquids
  - - - made of 2 diff metal strips joined together. when heated or cooled, flat strip bends because on metal expands or contracts more than the other
      - pg 154
- - - - expand in hot weather, small gaps in tracks allow for expansion. if gaps are too small, tracks will bend or buckle. pg 156
    - - concrete surfaces such as roads and paths expand when heated. small gaps found every few metres in concrete roads and gpas are filled with soft material which is easily squeezed when concrete expands
    - - in hot weather, overhead electricity cables or telephone lines expand and sag, in cold weather, they contract and tighten. if they become too tight, wires can break. to avoid this, overhead wires are not stretched tightly when they are installed
    - - most modern bridges are made of concrete or steel. bridge surface gets longer on hot days and shorter on cool days. in order to allow this movement, bridges have expansion gaps or rollers. with rollers, one end of bridge is fixed while other end is free to move on rollers
    - - pipes carrying hot water or steam have expansion loops.without these loops, force produced by expanding pips can cause them to buckle and break. pg 158
    - - if hot water is poured onto thick glass, glass often cracks. inner layer in contact with hot water expands more quickly than outer glass layer (which is cooler). unequal expansion breaks glass. glassware used for heating at home and in lab is made of heat resistant glass. glass expands very little when heated,
  - - - bimetallic strip is made into coil. as temp changes, 2 metal strips expand or contract unequally, causing coil to unwind or tighten. pointer moves over scale to show temperature
        pg 159
    - - bimetallic strips are used in thermosats
      - keep temperatures constant in appliances such as electric irons, refrigerators and rice cookers. pg 159
- - - - good conductors of heat are used when heat needs to be transferred quickly from one place to another. insulators are used to reduce heat transfer from one place to another. pg 161
- - - - there is heating element at bottom of kettle which heats water. hot water(which is less dense) rises and cold water(which is denser) sinks. convection current forms and eventually all water becomes hot
      - pg 164
    - - many large buildings and hotels have hot water systems. hot water from boiler(which is less dense) rises and water from colder tank (which is denser) sinks into boiler. convection currentforms as shown in pg 164. this cycle ensures continuous supply of hot water
    - - pg 165
    - - pg 165
- - - - shiny or white surfaces reduce amount of energy absorbed from surroundings by reflecting radiation. similarly, they can reduce amount of heat lost from container by reflecting heat from inner walls. thus, heat remains in container
  - - - black/white,colored, rough smooth
      - darker or rougher surface, more heat gained or lost per second
    - - greater surface area of body, more heat gained or lost per second
    - - greater temperature difference between body and its surroundings, more heat gained or lost per second
- - - - release large amounts of carbon dioxide into atmosphere
    - - animals breathe out carbon dioxide. when organisms die, they decay. decaying matter also releases carbon dioxide