Temperature:

The physical quantity that tells how warm or cold a body is with

respect to some standard body.

1. Proportional to the average kinetic energy of the particles of a

body.

2. Determines the direction in which thermal energy flows

between substances.

Thermal Energy

The total kinetic and potential energy of all the molecules of a

body due to their motion. (Internal Energy)

Heat

Thermal energy that is transferred from one object to another

because of the difference in temperature.

Temperature and Heat Measurements / Units

Temperature is measured by an instrument called a Thermometer. 4 Types of Thermometers: 1. Solid 2. Liquid 3. Gas 4. Thermocouple

Solid Thermometers (Metal) Contains a bi-metal coil (2 metals bonded together with different expansion rates) which winds or unwinds when temperature changes. (Typically brass and steel/iron) The bimetallic strip thermometer, because it is made of metal, is good at controlling very sensitive things. (House furnace, ovens, refrigerator, etc.) The longer the bimetal element the better accuracy.

Liquid Thermometer

Simply put, alcohol and mercury expand when heated. In a

standard bulb thermometer, this means the liquid will rise as the

temperature increases.

Mercury (silver): Used in hotter temps

(-40ºC to boiling Point)

Alcohol (red or blue dye): Used in colder temps (-129ºC to 78ºC)

Glass tube filled with liquid (often mercury or alcohol) that

expands/contracts with air temperature

Gas Thermometer

A Gas filled bulb to which a pressure gauge is attached. Usually

this gas is hydrogen or helium. This is used on a large range of

temperatures.

Gas thermometers measure temperature by changes in the

pressure of a gas kept at constant volume

Thermocouple

A device consisting of two different conductors (usually metal

alloys) that produce a voltage, proportional to a temperature

difference, between either end of the two wires.

• Applications include temperature measurement for large gas

ovens, diesel engines, and other industrial processes.

• Temperatures range from -270ºC to 700ºC.

Note: The three types of thermometers (solid, liquid and gas) all operate on the principle that substances expand when heated and contract when cooled. Making of a thermometer: http://www.youtube.com/watch?v=SZvAmvGQKEA http://www.youtube.com/watch?v=XEv2Q7ASBPg

Four major Temperature scales:

(We will only deal with the 1st three)

• Celsius

• Fahrenheit

• Kelvin

• Rankine

Temperature is a physical quantity which gives us an idea of how

hot or cold an object is.

The temperature of an object depends on how fast the atoms and

molecules which make up the object can shake, or oscillate. As an

object is cooled, the oscillations of its atoms and molecules slow

down.

For example, as water cools, the slowing oscillations of the

molecules allow the water to freeze into ice. In all materials, a

point is eventually reached at which all oscillations are the

slowest they can possibly be.

The temperature which corresponds to this point is called

absolute zero. (Note that the oscillations never come to a

complete stop, even at absolute zero.)

Most people are familiar with either the Fahrenheit or the Celsius

scales, with temperatures measured in degrees Fahrenheit (ºF)

or degrees Celsius (ºC) respectively.

The Fahrenheit and Celsius scales coincide only at one

temperature: −40 degrees

(i.e. −40 °F and −40 °C describe the same temperature).

Fahrenheit scale:

Water Freezes: 32º F

Water Boils: 212º F

Absolute zero: -459º F

Celsius scale:

Water Freezes: 0º C

Water Boils: 100º C

Absolute zero: -273º C

The Kelvin (symbol: K) is a unit increment of temperature and is

one of the seven SI base units. The Kelvin scale is a

thermodynamic (absolute) temperature scale where absolute zero,

the theoretical absence of all thermal energy, is zero (0 K).

This definition also exactly relates the Kelvin scale to the Celsius

scale. Absolute zero—the temperature at which nothing could be

colder and no heat energy remains in a substance—is, by

definition, exactly 0 K and −273 °C.

Scientists - especially those who study what happens to things

when they become very, very cold - commonly use the Kelvin

scale, with temperatures measured in Kelvin (K).

This scale uses the same temperature steps as the Celsius scale,

but is shifted downward. On this scale, water freezes at 273 K

and boils at 373 K.

Kelvin scale:

Water Freezes: 273 K

Water Boils: 373 K

Absolute zero: 0 K

FROM Celsius TO Celsius

Fahrenheit °F = (°C × 9⁄5 )+ 32 °C = (°F − 32) ×

5⁄9

Kelvin K = °C + 273 °C = K − 273

For temperature intervals rather than specific temperatures:

• 1 °C = 1 K • 1 °C = 1.8 °F

FROM Fahrenheit TO Fahrenheit

Celsius °C = (°F − 32) × 5⁄9 °F = (°C ×

9⁄5 ) + 32

Kelvin K = (°F + 459) × 5⁄9 °F = (K ×

9⁄5 )− 459

For temperature intervals rather than specific temperatures:

• 1 °F =

5⁄9 °C

FROM Kelvin TO Kelvin

Celsius °C = K − 273 K = °C + 273

Fahrenheit °F = (K× 9⁄5 ) - 459 K = (°F +459)×

5⁄9

http://www.google.com/url?sa=i&rct=j&q=temperature+freezing+points&source=images&cd=&cad=rja&docid=vCgUmumPFCJUHM&tbnid=4NOb4XmOntedaM:&ved=0CAUQjRw&url=http://jersey.uoregon.edu/~imamura/122/lecture-3/lecture-3.html&ei=PZcFUc2HCqvy0wGsw4C4BQ&bvm=bv.41524429,d.dmQ&psig=AFQjCNHwXk-ZmkbNvcLLY3GSUtaXL5Gelg&ust=1359407293552591

68 ºF

Convert the following to the Celsius and Kelvin scale:

5 ºF

176 °F

20 ºC 293 K

Celsius Kelvin

-15 ºC 258 K

80ºC 353 K

30ºC

Convert the following to the Fahrenheit and Kelvin scale:

5ºC

-20°C

86 ºF 303 K

Fahrenheit Kelvin

41 ºF 278 K

-4 ºF 253 K

Fahrenheit scale:

Ethyl alcohol boils at 78.5 °C and freezes at -117 °C. Convert

these temperatures to the (a) Fahrenheit scale and (b) Kelvin

scale.

Kelvin scale:

173 °F

Boiling Freezing

-179 °F

351.5 K 156 K

How do we measure heat?

calorie (cal)

• The calorie is the amount of heat needed to increase the temperature

of 1 gram of water by 1 °C.

British Thermal Unit (B.T.U)

• The amount of heat needed to raise the temperature of 1 lb. of water

1 °F.

Food Calories are measured in kcal

1 Cal = 1000 cal = 1kcal

Conversions:

• 1 cal. = 4.19 Joules

• 1 B.T.U. = 250 cal.

• 1 Calorie (food) = 1000 cal. = 1 kcal.

Mechanical Equivalent of Heat:

S.I.: 4.19 J of work converts to 1 calorie of heat.

B.E.: 778 ft-lbs of work converts to 1 B.T.U. of heat.

Formula for work:

W = J · Q

W = Work (Joules)

J = 4.19 J/cal (constant)

Q = Heat (calories)

a. How much work is required for a 1,500 Calories per day

person to be a couch-potato?

6,285,000 J

b. What is their Power consumption?

6,285,000 J / 86,400 seconds = 72.74 W

– We’re like light bulbs, constantly putting out heat