Temperature Chapter 45 – Page 306

How do we measure how hot or cold an object is?

Temperature Temperature is a measure of how hot an object is Thermometers A long glass tubed closed at both ends Contains either alcohol or mercury What happens to the liquid inside?

Thermometers Liquid expands when heated Contracts when cooled

Questions to make you think Foil and the cotton towel are both at the same temperature – so why does the foil feel colder? A candle needs oxygen to burn, which is why if we want to resuscitate a dying fire we blow on it. So why does blowing on a candle put it out? Why does it get colder as you climb up a mountain, even though you’re getting closer to the sun

Why might a glass crack when you pour boiling water into it? If you lick a frozen pipe why will your tongue stick to the pipe? Why are ice cubes much better at cooling a drink that the equal amount of iced water? Why is a scald from steam much more serious that a burn from boiling water?

When stepping out of bed on a cold morning, why does it feel colder if your feet touch say, a marble floor rather than a floor with carpet even though both are at the same temperature? How does perspiration (sweating) help to keep us cool? Many Arabs wear dark clothing in warm weather, even though dark clothes are better at absorbing heat than white clothes. Any idea why?

Is heat and temperature the same? Think Pair Share Imagine 2 hot water bottles, one half filled and the other full with boiled water. Which one will keep you warm for longer?

The amount of heat in a substance depends on its temperature, its mass, and what the substances are Think about these tow scenarios

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Today we will… 1.Recap on states of matter 2.Look at the concept of latent heat\ 3.Plot a temperature plot of ice changing to water vapor to demonstrate latent heat

Changes of State SolidLiquidGas What are the 3 states of matter? How do we move from one state to another? Evaporation Melting

Change of State Adding heat gives energy to the molecules allowing them to move faster This increased movement changes the state from solid to liquid and then to gas Removing heat means the molecules slow down and so change back from gas to liquid to solid

Phet Animation

To Determine the Melting Point of Ice

To Determine the boiling point of water

“Hidden Heat” What sort of a temperature graph do you think I would get from this scenario?

The experiment Set up apparatus:

Method 1.Turn on hot plate and start recording temperature every minute 2.Do this until the water starts to boil 3.Record your results 4.Plot the point on graph paper

Results Table Time (min)Temperature (°C)

Latent Heat