2. Temperature
• It is not simply “how hot or cold something is”
• Hot and cold are relative
• Temperature is, specifically, a measure of the average kinetic
energy of the particles in an object
• All matter is made of particles that are constantly moving!
(Remember the movements of solids, liquids and gasses)
• The more the particles are moving, the more kinetic energy,
therefore, higher temperature
3. How do we measure temperature?
• Thermometers
• Thermometers can measure temperature due to thermal
expansion.
• Thermal expansion is an increase in the size of a substance in
response to an increase in the temperature of the substance.
• As a substance’s temperature increases, its particles move faster
and spread out. There is more space between them = expansion.
4. The temperature scales
• You will have to know this
for your SOL test!
• 0K = absolute zero
• Absolute zero is the
temperature at which all
molecular motion stops.
5. Heat
• Heat is the energy transferred between objects that are different
temperatures.
• When two things at different temperatures come into contact,
energy is transferred from the object with the higher temperature
to the object that has the lower temperature.
• The form of energy being transferred is thermal energy. Thermal
energy is the total kinetic energy of the particles that make up a
substance.
• More thermal energy = higher temperature
6. Quick check!
• Why do we use temperature instead of “hot” and “cold”?
• What are the three temperature scales?
• What is absolute zero?
7. 3 ways to transfer thermal energy
• Conduction
•Convection
•Radiation
8. Conduction
• Thermal conduction is the
transfer of thermal energy
from one substance to another
through direct contact.
• Substances that conduct
thermal energy well are called
thermal conductors.
• Substances that do not
conduct thermal energy well
are called thermal insulators.
9. Convection
• Convection is the transfer of
thermal energy by the circulation
or movement of a liquid or gas.
11. Quick check!
• What are the three types of thermal energy transfer?
• What are some key words that can let you know that the type of
transfer is conduction?
• Convection?
• Radiation?
12. Heat and Temperature Change
• Remember the concepts of
insulators and conductors
• Different substances have
different thermal conductivity
• Thermal conductivity is the
rate at which a substance
conducts thermal energy.
13. Specific Heat
• How easily does a material
change temperature?
• Specific heat is the amount of
energy needed to change the
temperature of 1 kg of a
substance 1 degree C. (p 285
Holt)
• The energy is measured in
joules.
14. States of Matter
• Remember: states of matter
are the physical forms of
matter, which include solid,
liquid and gas.
• A change of state is a change
of a substance from one
physical state to another.
• Is change of state a physical or
chemical change?
15. Changes
• Heat can be involved in both
physical changes (change of
state) and chemical changes
• How do new bonds form in
chemical reactions?
16. Food and Chemical Energy
• Where do we get energy?
• Energy that your body can use is released when chemical
compounds such as carbohydrates are broken down. Energy is
released in chemical reactions.
• You can find out how much chemical energy is in food by looking
at the CALORIES on the nutrition label
• The calorie is the unit of energy in food = a measure of heat
• 1 calorie = 4184 J
