Transcript Daily Science pg. 40

Daily Science
pg. 40
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Convert the following temperatures:
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45oC into Kelvin
45o C into Fahrenheit
309 K into Fahrenheit
98oF into Kelvin
299 K into Celsius
8oF into Kelvin
Give an example of conduction, convection, and radiation. Explain why
over exposure to the sun or to X-rays can be harmful.
Calculate the kinetic energy of a wheel that has a mass of 65 kg and is
rolling with a velocity of 4.5 m/s.
Calculate the potential energy of a bomb that is falling from a height of 48
m and has a mass of 15 kg.
Calculate the potential energy of a ball dropped from E-wing that weighs
4.8 N and is being dropped 6 m.
Calculate the mass of a person in a wheelchair if they are rolling at a
velocity of 0.7 m/s and have 20 j of kinetic energy.
Specific Heat
Pg. 41
Conductors and insulators
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Conductor- a material through which energy
can be transferred as heat.
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Examples:
Insulator- a material that transfers energy
poorly.
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Examples:
Specific Heat
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The amount of energy needed to change the
temperature of a substance by a certain
amount is what determines if a substance will
be a good or poor conductor.
Specific heat is the quantity of heat needed to
raise the temperature of 1 kg of substance by
1 K.
Specific heat is a physical property.
Specific heat values
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Every substance has a unique specific heat.
The letter C is used to denote specific heat.
Water has one of the highest specific heat
values (4,186 J/kg x K)
Calculating Specific Heat
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Heat= mass x temperature change x specific
heat value
Q = m x ∆T x C
Units:
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MassTemperatureSpecific HeatHeat-
Practice Problems
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How much energy is needed to increase the
temperature of 0.755 kg of iron from 283 K to
403 K?
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How much energy must a refrigerator absorb
from 225 g of water to decrease the
temperature of the water from 35oC to 5oC?
State changes
Heat makes objects change state.
 Energy of a substance either raises the
substance’s temperature or changes the
substance’s state. NOT BOTH AT THE
SAME TIME.
 This is why there
are horizontal lines
on a phase change
diagram.
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