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# DO NOW: Energy Transformations - PowerPoint PPT Presentation

DO NOW: Energy Transformations. Match the different types of energy transformation in each picture. IRON WINDMILL MIXER SUN a. b. c. d. 1. Electrical to Mechanical ___________

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DO NOW: Energy Transformations

Match the different types of energy transformation in

each picture.

IRON WINDMILL MIXER SUN

a. b. c. d.

1. Electrical to Mechanical ___________

2. Nuclear to Thermal ___________

3. Mechanical to Electrical ___________

4. Electrical to Thermal ___________

### Temperature and Heat

Temperatureis the measure of the average

kinetic energy of the particles of matter. You need

a thermometer to measure temperature.

There are three types of temperature scales:

• Fahrenheit(F)

• Celsius(C)

• Kelvin(K).

the Celsius scale is more compatible with

temperature measurements used in the metric

system. Even though the Fahrenheit and

Celsius temperature scales are extremely useful

for various applications, the Kelvin scale is used

to measure temperature in the International

System of Units (SI).

The difference between the Kelvin and Celsius

scales is the location of the zero point. The zero

point of the Kelvin scale (0K), called absolute

zero, corresponds to -273C. Absolute zero is

the point at which the motion of particles of

matter ceases.

Conversions between these two scales can be

made by using the following formulas:

C + 273 = K

K – 273 = C.

Heat is defined as the transfer of kinetic energy

from a hotter object to a colder object. Heat is

measured in units of joules or calories.

• A hot drink left in a cold place will always lose heat to the surroundings. It will get cooler until eventually it is at the same temperature as its surroundings. But if it is inside a good thermal insulator (such as a thermos flask), it will lose the heat very slowly.

Reactions that release heat to its surroundings

are called exothermic reactions. When an

exothermic reaction releases heat to its

surroundings, the temperature of the

surroundings increases.

Reactions that absorb heat are called

endothermic reactions. When an endothermic

reaction absorbs heat, the temperature of its

surroundings decreases.

The size of the temperature increase depends

on how much heat is released and on the heat

capacity of the surroundings. The heat capacityof

an object is the amount of heat needed to raise the

temperature of the object by 1 Celsius degree. The

heat capacity of an object depends on its mass and

its composition. A large mass of water can absorb a

large quantity of heat with only a small

temperature increase.

The heat capacity of 1 gram of a substance is

called its specific heat. The specific heat is a

physical property of the substance like its color

and melting point. Different substances have

different capacities for storing energies.

SubstanceSpecific Heat (J/g C)

H2O (l) 4.184

H2O (s) 2.03

Al (s) 0.89

C (s) 0.71

Fe (s) 0.45

Hg (s) 0.14

The amount of heat given off or absorbed can

be calculated by the following formula:

(Tf - Ti)

Q = m x T x Csp

Q = heat (measured in Joules (J) or calories (cal))

m = mass (g)

T = change in temperature (T = final temperature (Tf) – initial temperature (Ti))

Csp= specific heat (J/gC or cal/gC)

• If the specific heat of water is 4.184 J/gC,

how much heat must be added to 5 g of

aluminum to raise its temperature by 2 Celsius

degrees?

Q = m x T x Csp

Q =

m =

T =

Csp=

2. The specific heat of aluminum is 0.89 J/g C. How much heat is required to raise the temperature if 16 grams of aluminum from 25C to 75C?

Q = m x T x Csp

Q =

m =

T =

Csp=

• A sample of KCl dissolves in 75g of H2O. The temperature changes from 21.6°C to 31°C. How much heat was exchanged?

(Csp of water = 4.184 J/g°C or 1 cal/g°C)

Q =

m =

 T =

Csp=

Q =

m =

T =

Csp=