Temperature, Heat - PowerPoint PPT Presentation

1 / 16
About This Presentation
Title:

Temperature, Heat

Description:

Temperature, Heat & Expansion Temperature - The quantity that tells how hot or cold something is compared with a standard. Measuring temperature: A common thermometer ... – PowerPoint PPT presentation

Number of Views:709
Avg rating:3.0/5.0
Slides: 17
Provided by: qmi
Category:

less

Transcript and Presenter's Notes

Title: Temperature, Heat


1
Temperature, Heat Expansion
2
  • Temperature - The quantity that tells how hot or
    cold something is compared with a standard.
  • Measuring temperature
  • A common thermometer measures temperature by
    showing the expansion contraction of a liquid
    in a glass tube using a scale.
  • the liquid is usually mercury or colored
    alcohol

3
Temperature Scales
  • Celsius
  • - most widely used scale
  • - international scale
  • - 00c temperature at which water freezes
  • - 1000c temperature at which water boils
  • Fahrenheit
  • used commonly in the U.S.
  • 32o temperature at which water freezes
  • 212o temperature at which water boils
  • Kelvin
  • used in scientific research
  • degrees are the same as Celsius and are called
    Kelvin
  • 0oK absolute zero (0oK -273oC)
  • Absolute zero is the temperature at which a
    substance has NO kinetic energy.

4
  • Temperature is proportional to the average
    kinetic energy.
  • As temperature increases kinetic energy
    increases.

5
Heat
  • Heat the energy that transfers from one object
    to another because of a temperature difference.
  • HEAT IS ENERGY
  • Heat is energy in transit from a body of higher
    temperature to one of lower temperature
  • The energy resulting from heat flow in Thermal
    energy.

6
Thermal Equilibrium
  • What is thermal equilibrium???
  • When objects in thermal contact with each other
    reach the same temperature and no heat flows
    between them.
  • ex to read a thermometer we wait until the
    liquid stops moving. This is the point when the
    liquid in the thermometer and the substance
    being measured have reached thermal equilibrium.

7
Internal Energy
  • The grand total of all energies in a substance
    is the internal energy.
  • A substance does not contain HEAT, it contains
    ENERGY !!!
  • This includes
  • The KE of moving molecules and atoms of a
    substance.
  • The PE due to the forces between molecules or
    atoms.

8
Measuring Heat
  • Heat is measured in calories.
  • A calorie the amount of heat required to raise
    the temp. of 1g water, 1oC.
  • A kilocalorie 1000 calories
  • Kilocalories are the heat unit used in rating
    foods. Kilocalories are often referred to as
    Calories. (with a capitol C)

9
Specific Heat Capacity
  • Specific heat is the quantity of heat required
    to raise the temp. of a unit of mass of a
    substance by 1 degree.
  • Different substances have different capacities
    for storing internal energy
  • (re ability to hold heat)
  • and
  • require specific quantities of heat to raise the
    temp. of a given mass a specific number of
    degrees.

10
Example
  • 1g of water requires 1 calorie to raise the
    temp. 1oC.
  • WHILE
  • 1g of iron requires 1/8 as much energy to raise
    the temp. 1oC.
  • Water absorbs more heat per gram that iron for
    the same temperature change.
  • So water has a higher Specific Heat.
  • (BTW water is considered to have a very high
    sp.heat)

11
Thermal Expansion
  • When the temp. of a substance increases the
    molecules move faster (increase KE)
  • This results in the EXPANSION of the substance.
  • With few exceptions all forms of matter (solid,
    liquid gas) expand when heated
  • and
  • contract when cooled.

12
Heat Transfer

13
Conduction
  • Conduction heat transfer within and between
    different materials in direct contact. (molecule
    to molecule)
  • conductor material that conducts heat well
    (metal)
  • insulator material that delays the transfer of
    heat (wood)

14
  • Poor conductors good insulators
  • Good conductors poor insulators
  • Which feels colder barefeet on tile or carpet?
  • The tile because it is a good insulator. The
    heat moves from your feet to the tile.
  • Does a blanket make you feel warmer?
  • The blanket is a good insulator and delays the
    transfer of heat from your body to the air.

15
Convection
  • Convection is when heat is transfer through a
    current in a fluid.
  • fluids can be either liquids or gases
  • examples
  • - Air in contact with a hot stove rises and
    warms the region above.
  • Water boils through convection
  • convection currents stir our atmosphere

16
Radiation
  • Radiation is the transfer of heat through
    electromagnetic waves. (UV light, visible light,
    infrared, microwaves, radio waves, etc.)
  • Examples
  • The sun
  • a lightbulb
  • a fireplace
  • Any energy, including heat, that is transmitted
    by radiation is called radiant energy.
Write a Comment
User Comments (0)
About PowerShow.com