1. Science 7: Unit C – Heat and Temperature Topic 2: Measuring Temperature

2. What is Temperature? First, what is heat? Heat is the energy that the particles in a substance have. All particles are moving. The faster they move, the hotter the substance gets. First, what is heat? Heat is the energy that the particles in a substance have. All particles are moving. The faster they move, the hotter the substance gets. Temperature is a measurement of the AVERAGE amount of energy the particles have. Temperature is a measurement of the AVERAGE amount of energy the particles have.

3. How can you tell the temperature of something? Easiest way is to put your hand over something to feel the heat it gives off. Easiest way is to put your hand over something to feel the heat it gives off. With a flame, you can tell how hot the flame is by the color of the flame. Blue is hotter than yellow which is hotter than red. With a flame, you can tell how hot the flame is by the color of the flame. Blue is hotter than yellow which is hotter than red. To be more precise when describing temperature, we need to give it a number value. To be more precise when describing temperature, we need to give it a number value.

4. Why use a temperature scale? To be accurate when talking about temperature a scale should be used. To be accurate when talking about temperature a scale should be used. A scale is created when two different points are chosen and the gap between them are split up into EVEN units. A scale is created when two different points are chosen and the gap between them are split up into EVEN units. For example, Anders Celsius based his Celsius scale on the properties of water: he chose his zero point to be the temperature where water freezes and his 100 degree point to be the temperature where water boils. He then split up the gap into 100 degrees all equal to each other. For example, Anders Celsius based his Celsius scale on the properties of water: he chose his zero point to be the temperature where water freezes and his 100 degree point to be the temperature where water boils. He then split up the gap into 100 degrees all equal to each other.

5. The Kelvin Scale The Kelvin scale is the one used by scientists. The Kelvin scale is the one used by scientists. A unit of Kelvin is equal to one degree in the Celsius scale. A unit of Kelvin is equal to one degree in the Celsius scale. The ABSOLUTE ZERO value in the Kelvin Scale is the temperature at which the last non-solid, helium, freezes. Absolute zero is equal to -273.15C. The ABSOLUTE ZERO value in the Kelvin Scale is the temperature at which the last non-solid, helium, freezes. Absolute zero is equal to -273.15C. It is impossible to reach absolute zero as long as there is energy in the universe. It is impossible to reach absolute zero as long as there is energy in the universe.

6. What is Infrared Radiation? Radiation given off by objects with thermal energy. The hotter the object, the more intense the radiation. Radiation given off by objects with thermal energy. The hotter the object, the more intense the radiation. IR is the only form of thermal energy that can travel through space. The sun’s IR waves travel through space for 8 minutes before reaching Earth. IR is the only form of thermal energy that can travel through space. The sun’s IR waves travel through space for 8 minutes before reaching Earth. Infrared radiation can be detected by species of birds and reptiles as well as special IR goggles and scopes. Infrared radiation can be detected by species of birds and reptiles as well as special IR goggles and scopes.

7. The Thermometer Is a device used to measure temperature. Is a device used to measure temperature. Early thermometers used air or water to measure temperature, however they lacked a proper scale so you couldn’t attach a number to the temperature. Early thermometers used air or water to measure temperature, however they lacked a proper scale so you couldn’t attach a number to the temperature. Modern thermometers use a scale (number value) to give more accurate readings. Modern thermometers use a scale (number value) to give more accurate readings.

8. Thermal Devices All thermal devices contain three parts: All thermal devices contain three parts: 1. Sensor – material which is affected by changes in temperature. Most devices use a bimetallic strip or liquid mercury. 1. Sensor – material which is affected by changes in temperature. Most devices use a bimetallic strip or liquid mercury. 2. Signal – Usually if a certain temperature is reached an electrical circuit is closed and electricity is created. 2. Signal – Usually if a certain temperature is reached an electrical circuit is closed and electricity is created. 3. Responder – If the electricity is created it usually triggers a mechanism to start. 3. Responder – If the electricity is created it usually triggers a mechanism to start.

9. Example - Furnace 1. Sensor – Bimetallic coil curls and uncurls as the temperature changes. 1. Sensor – Bimetallic coil curls and uncurls as the temperature changes. 2. Signal - If it gets too cold, the coil completes a circuit with a ball of mercury and electricity is created flows down the circuit. 2. Signal - If it gets too cold, the coil completes a circuit with a ball of mercury and electricity is created flows down the circuit. 3. Responder – When the electricity reaches the furnace, it turns it on and the furnace heats the house. 3. Responder – When the electricity reaches the furnace, it turns it on and the furnace heats the house.

10. Thermocouple Is a device which combines temperature and electricity. Is a device which combines temperature and electricity. Wire of two different metals are twisted together. When heated, these wires create an electrical current which can be used to turn a switch on or off. Wire of two different metals are twisted together. When heated, these wires create an electrical current which can be used to turn a switch on or off. They can measure high temperatures, but not low temperatures. They can measure high temperatures, but not low temperatures.