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

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DO NOW: Energy Transformations

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Do now energy transformations

DO NOW: Energy Transformations

Match the different types of energy transformation in

each picture.

IRONWINDMILL 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

Temperature and Heat


What is temperature

What is temperature?

Temperatureis the measure of the average

kinetic energy of the particles of matter. You need

a thermometer to measure temperature.


Temperature scales

Temperature Scales

There are three types of temperature scales:

  • Fahrenheit(F)

  • Celsius(C)

  • Kelvin(K).


Do now energy transformations

Although the Fahrenheit scale is widely used,

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).


What is absolute zero

What is absolute zero?

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.


Temperature conversions

Temperature Conversions

Conversions between these two scales can be

made by using the following formulas:

C + 273 = K

K – 273 = C.


What is heat

What is heat?

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.


Example

Example

  • 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.


Exothermic reactions

Exothermic Reactions

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.


Endothermic reactions

Endothermic Reactions

Reactions that absorb heat are called

endothermic reactions. When an endothermic

reaction absorbs heat, the temperature of its

surroundings decreases.


What is heat capacity

What is heat capacity?

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.


What is specific heat

What is specific heat?

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.


Do now energy transformations

SPECIFIC HEAT OF SOME SUBSTANCES

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


Heat calculations

Heat Calculations

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)


Sample problems

SAMPLE PROBLEMS:

  • 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=


Do now energy transformations

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=


Do now energy transformations

  • 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=


Do now energy transformations

  • What is the specific heat of aluminum if the temperature of a 28.4g sample of aluminum is increased by 8.1C when 207 J of heat is added?

    Q = m x T x Csp

Q =

m =

T =

Csp=


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