POS  Key Terms: temperature  K2d:  Distinguish between heat and temperature; and explain temperature, using the concept of kinetic energy and the particle model of matter  K1c:  Identify and explain uses of devices and systems to generate, transfer, control or remove thermal energy (describe how a furnace and wall thermostat keep a house at a constant temperature

POS cont’d  K3d:  explain the operation of technological devices and systems that respond to temperature change (thermometers, bimetallic strips, thermostatically-controlled heating systems)

Materials  Thermometer  Pail of hot, cold, room temperature water  Thermostat  Bi-metallic strip  Lighter/candle  Thermometer  Hot plate  Beaker of water

Unit C: Heat and Temperature Topic 2: Measuring Temperature

Exothermic Reactions  Exo: release  Thermic: heat energy  Reactions that break the bonds between molecules, releasing heat  Feels hot  Ex. Whoosh bottle  =0aqH1JgmZ_4&safety_mode=true &persist_safety_mode=1&safe=acti vehttp:// ?v=0aqH1JgmZ_4&safety_mode=tr ue&persist_safety_mode=1&safe=a ctive

Endothermic reactions  Endo: absorb  Reactions that create bonds between molecules, absorbing heat  Feels cold  Ex. Ice packs

Are humans good thermometers?  Can you tell whether something is hot or cold?  We can guess the relative temperature by touch, or see that a red hot coal is hot, but cannot make a precise measurement  It is dangerous to measure temperature by touch (burn/frostbite)  Experiment: hot/cold/room temperature water buckets

What is temperature?  Hot or cold right?  Three important details:  Temperature is a relative measurement of hot or cold  Measured on a scale ( o F, o C, K)  Average kinetic energy of particles in a substance

Heat vs. temperature  Heat is the energy of particles  Temperature is a relative measure of this (kinetic) energy on a scale  The particle model of matter helps to explain that as temperature increases, particles have more energy, move faster and have greater spaces between them  Pg

Heat or Thermal Energy is measured in:  Joules (J): heating bills  Degrees:  Fahrenheit ( o F)  Celsius ( o C)  Kelvin (K)  Pg

Celsius Scale  Anders Celsius ( )  Based his scale on the freezing and boiling point of water  0 0 C and C  Note: this only works at sea level!  What is the boiling point of water in Calgary?  Our altitude is higher, so the boiling point will be lower (less atmospheric pressure holding particles together)  Try it out!

Kelvin Scale  Lord Kelvin ( )  Decided that the coldest possible temperature, where all particle motion stops, is absolute zero (hypothetical)  0K= o C  0 o C= K

What temperature?  Absolute zero  Freezing point of water  Room temperature  Body temperature  Boiling point of water in Calgary  Boiling point of water

What do we use to measure temperature?  Hands? Eyes? No!  Measurement devices (4)  1. Thermometer:  As the temperature increases, the liquid inside expands, rising in the glass tube  As temperature decreases, the liquid inside contracts  Mercury-poisonous vs. alcohol  Limitations: short temperature range

2. Thermocouple  Wires that generate electric current when heated  Good for measuring very hot temperatures, where liquid in a thermometer would boil ex. in your oven

3. Infrared Thermogram  Detects infrared radiation or heat, a section of the electromagnetic radiation (EMR) spectrum that we cannot see

Side note-black lights 

4. Bimetallic strip Bi- two, metals  One metal expands more than the other when heated  Bimetallic strips are used  in recording thermometers (see pg 200) for long-term temperature readings  In thermostats  To turn on/off refrigerators and air conditioners

Thermostat  Where is the class thermostat? In the portables?  *show thermostat

How a thermostat works  Coordinates with the furnace . glass vial are three wires. One wire goes all the way across the bottom of the vial, so the mercury is always in contact with it. One wire ends on the left side of the vial, so when the vial tilts to the left, the mercury contacts it -- making contact between this wire and the one on the bottom of the vial. The third wire ends on the right side of the vial, so when the vial tilts to the right, the mercury makes contact between this wire and the bottom wire

Thermostats  The bimetallic strip acts as a thermometer  When it is cold, the strip will contract  When it is warm, the strip will expand, tilting the mercury away from the wire, breaking the connection  Why is mercury used? It is the only liquid metal, and therefore conducts electricity.

Energy saver tip:  Turn down the thermostat!  Dress warmly, put on a blanket  Keep the temperature low when you are not at home-programmable thermostats will make this easy for you

Assignment:  Read Heat info sheet  Read Temperature Scales info sheet  Activity pg 198 Boiling Hot, Freezing Cold  Topic 2 Review Q’s pg 201 #1,2,5  Heat + Temperature Reading Assignment T2-3