1. heat

2. Measuring temperatures:
Expansion = an increase in the volume of an object or substance; for most substances, adding heat causes it.
Contraction = a decrease in volume of an object or substance; usually with the removal of heat.
Since solids, liquids, and gases usually expand when heated and contract when cooled, almost any substance can be used in a thermometer.
Not all thermometers rely on expansion or contraction; some rely on electricity or battery power to operate. The choice usually depends on the way the thermometer will be used.

3. Measuring temperatures:
Liquid Thermometers:
Use the expansion and contraction of a liquid to measure temp.
When warmed, the liquid (usually coloured ethyl alcohol) expands in the bulb and is forced up the narrow bore
clinical thermometer outdoorthermometer

4. Measuring temperatures:
The Thermostat:
Can be used to measure temperature in a room or in an appliance (such as a furnace)
It can also switch appliances on or off at a pre-set temperature
It can act as a feedback system
Use the expansion and contraction of solids to measure temp.
They contain a strip made of two metals (bimetallic strip) – because they are different substances, when they are heated or cooled, the two metals will expand or contract by different amounts causing the strip to bend
The amount of bending depends on the temperature

5. Measuring temperatures:
The Thermostat:

6. Measuring temperatures:
The Thermocouple:
Uses electricity to operate
Contains two wires, each a different metal, that are joined/coupled at one end
When two different metals touch each other, a tiny electrical current is generated
The amount of electricity depends on the temperature
The other ends of the wires are connected to a meter that measures electricity
By measuring the amount of electricity that flows through the meter, you can measure the temperature of the metal wires

7. Measuring temperatures:
The Thermocouple:

8. Temperature, heat, and the particle theory
All matter is composed of very small particles
All particles have spaces between them
Particles are in constant motion
Particles all have energy
Particles are held together by the attractive forces between them
The addition of heat energy causes particles to move faster thereby stretching their bonds

9. Temperature, heat, and the particle theory
Heat and Temperature:
Heat = energy (transfers from hotter substances to colder ones)
Temperature = a measure of the average energy of motion of the particles in a substance.
When heat is transferred to particles of cold water, for example,
→ particles will have more energy of motion → particles will move faster → temperature of the water rises

10. Temperature, heat, and the particle theory
Expansion and Contraction:
At high temperatures → particles have more energy → particles move more quickly → particles have more collisions → particles take up more space → substance expands
States of Matter:

11. Solid Liquid Gas Little spaces between particles
More space between particles than in a solid
Most space between particles
Particles have little energy
Particles have more energy than in a solid
Particles have the most energy
Little movement of particles (strongest attractive forces)
Particles move more than in a solid (weaker attractive forces)
Particles move more than in a solid or liquid (weakest attractive forces)
Shape - stays the same
- “definite” shape
Shape - can change because of container’s shape
Volume - stays the same
- “definite” volume
Volume – changes only with change in container’s volume

12. particle theory & changes of state
Change of State: