Energy
description
Transcript of Energy
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Energy
Kinetic energy = energy of motion
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Energy
Potential energy = stored energy
1. energy of position due to gravity
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Energy
Potential energy = stored energy
2. energy stored in
chemical bonds
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Law of Conservation of Energy
Energy can not be
created or destroyed,
only converted from
one form to another.
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When energy is RELEASED in a chemical reaction, it is called….
EXOTHERMIC
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When energy is ABSORBED in a chemical reaction, it is called….
ENDOTHERMIC
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Units of Energy
Energy is measured in JOULES
Also in calories or kilocalories (food)
How many calories are in a kilocalorie?
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Units of Energy
How many calories in the hamburger?
420 kilocalories
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What is temperature?
A measure of the average kinetic energy of the particles in a sample of matter.
All atoms are moving!
High temperature = moving faster
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Once again……
TEMPERATURE
=
AVERAGE KINETIC ENERGY
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Temperature Scales
Celcius:
water freezes water boils Zero degrees100 degrees
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Temperature Scales
Kelvin: 0 K = absolute zero (-460 oF)all motion of particles stops!
Water freezes @ 273 KWater boils @ 373 K
Kelvin never goes below zero (no negative numbers!)
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Temperature Scales
Kelvin = Celsius + 273
Celsius = Kelvin – 273
If it is 32O Celsius, what temperature is it in Kelvin?
If it is 100 Kelvin, what temperature is it in Celsius?
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Temperature Scales
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Standard Temperature
0 degrees Celsius
273 Kelvin
(in Table A)
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At what temperature does liquid nitrogen boil?
• 77 Kelvin
• -195 Celsius
• -320 Farenheit
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What is Heat?
Heat is the sum total of all the kinetic energy in a sample of matter.
How is heat different from temperature???
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Heat ≠ Temperature
Both the water in the bath tub and in the cup are at 25 oC
Which contains more HEAT?
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Heat Capacity
The amount of energy (in JOULES) needed to raise the temperature of the sample by 1 oC
Which water sample has a higher heat capacity?
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Specific Heat Capacity
The amount of energy (in JOULES) needed to raise the temperature of 1 gram of the sample by 1 oC
Which water sample has a higher specific heat ?
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Specific Heat
Specific heat measures how easily something can absorb (or then lose) heat.
LOW specific heat = little energy for something to
heat up.HIGH specific heat = lots of energy to heat
something up
Every substance has its own unique specific heat value.
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Specific Heat Capacity
In your experience, which substance below has a higher specific heat capacity (takes more energy to heat it up?)