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# science ;_;

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## Bagel Tribe

on 15 January 2014

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#### Transcript of science ;_;

Energy Flow in Global Systems

Quantity of Thermal Energy
Thermal Energy Transfer
in the Atmosphere
Hydrologic Cycle
Heat of Fusion
Quantity of Thermal Energy(Q): is when the amount of thermal energy absorbed or lost is changed
This is based off the temperature of the substance
The Equation
The equation for solving for "Q" is:
Q= mc(delta)t
2.2-2.3
m=mass(g)
c=heat capacity(J/g.*Celsius)
t=temperature difference
*To know what "Q" is you need to know the specific heat capacity(c)
Calorimeter
A device used to determine
how much thermal energy
is transferred. Any energy
that is lost or gained
counts as a temp. change
Solving for Heat......
what is the change in heat energy when 114.3g of water at 14.8*C is raised to 18.0*C?
(specific heat of water=4.18J/g
What is the change in heat energy when 114.3g of water at 14.8*C is raised to 18.0*C?
(Specific Heat of Water=4.18J/g*C)
How to do it..
write down formula
find out "delta t" by subtracting t(final) by t(initial)
fill in the formula
cross out all the units that have pairs
How the Work Should Look..
Q=mc(delta)t
q=?
m=114.3g
c=4.18J/g*C
delta t=t(final)-t(initial)
=18.0-14.8
=3.2*C
Q=(114.3g)(4.18J/g*C)(3.2*C)
Q=1,528.87J
Specific Heat Capacity
Specific Heat Capacity: the amount of energy required to raise the temperature of 1g of the substance by 1*C.
the amount of energy absorbed when 1mol of a substance changes from a solid to a liquid (without a temperature change)
Heat of Vaporization
amount of energy absorbed when 1mol of a substance changes from a liquid to a vapor (without a temperature change)
Heat of Solidification
the reverse (liquid to a solid)
Heat of Condensation
the reverse (vapor to a liquid)
*If the question asks you to convert it to KJ divide the answer by one thousand
When thermal energy is added the substance gains kinetic energy in its molecules. When a phase change occurs, instead of molecules gaining kinetic energy, it's absorbed by the force between the molecules. When these forces gain a sufficient amount of potential energy they're disrupted and the substance changes phases.
Calculations
Water of hydrosphere can be
present as liquid water, solid ice or snow or as water vapor in the atmosphere

Hfus = Q/n
Water leaves atmosphere as precipitation, some of the solid precipitation melts and returns to liquid phase.
Most of the liquid precipitation collects in lakes and rivers however a small amount goes into the soil

Hfus = heat of fusion (kJ/mol)
Q = thermal energy (kJ)
n = amount of the substance (mol)
All living organisms take in the water for cellular
processes then release water back into atmosphere
through precipitation, plants also use the water for photosynthesis
Theoretical Hfus of ice = 6.01 kJ/mol
Energy Transfer
Hvap = Q/n
Hvap = heat of vaporization (kJ/mol)
Q = quantity of thermal energy (kJ)
n = amount of the substance (mol)
When water changes phase thermal energy is released or absorbed however the temperature of water through phase change remains the same even though the quantity of thermal energy changes
When a change of state occurs bonds in the particles are broken however the temperature doesn't change because it only changes when kinetic energy changes and since energy is used to break the bonds there is no energy available to increase the kinetic energy
Since water molecules undergo many phase changes there is a lot of energy transferred in the biosphere without any temperature changes which helps to keep earth's temperature stable
theoretical Hvap of water = 40.65 kJ/mol
If the mass is given or required, the amount (n) must first be determined by converting from g to mol
n = m/M
n = amount of substance (mol)
m = mass of the substance (g)
M = molar mass of the substance (g/mol)
molar mass of ice = 18.02 g/mol
Conduction
Heat of Fusion and Heat of Vaporization
Convection
Conduction:
The transfer of thermal energy
through direct contact.
All particles have an average kinetic energy, during conduction, particles have a lower kinetic energy than usual - increases kinetic energy of particles around them.
The release of energy in waves or particles.
When energy from radiation hits particles in matter, it will be reflected or absorbed.

If the energy is absorbed - it will increase the kinetic energy of the particles, which will increase the temperature of the matter.
If a substance is a
higher temperature than its surroundings,
usually in the form of infrared radiation.
Convection:
The transfer of thermal energy through movement of particles from one location to another. This transfer usually occurs in fluids
A current is created, molecules move apart from each other and the material expands in volume. The less dense material would rise to the top, forming an upward convection current. When it contacts the cooler air at the surface, the material will cool and contract, that would increase the density and form a downward convection current.
When 27.05kJ of thermal energy is added to 4.50 mol of ice at 0.0°C, the ice melts completely. What is the experimental heat of fusion of water?
Hfus = Q/n
= 27.05kJ/4.50mol
= 6.0111111 kJ/mol
= 6.01 kJ/mol
When 5.00g of ice melts, 1.67kJ of thermal energy is absorbed. Calculate the experimental heat of fusion of ice. The molar mass (M) of ice is 18.02 g/mol
n = m/M
= 5.00g/18.02 g/mol
= 0.2774694 mol

Hfus = Q/n
= 1.67 kJ/0.2774694mol
= 6.01868 kJ/mol
= 6.0 kJ/mol
When 150g of water changes from liquid to vapor phase, 339kJ of energy is absorbed. Determine the experimental heat of vaporization of water, given that the molar mass (M) of water is 18.02 g/mol
n = m/M
= 150g/ 18.02 g/mol
= 8.32 mol

Hvap = Q/n
= 339kJ/ 8.32mol
= 40.745192kJ/mol
= 40.7 kJ/mol

The answers won't always be completely accurate to the theoretical values of a substances heat of fusion or vaporization.
Specific Heat
What is the specific heat of metal if it's mass is 26.86 and it requires 418.6J of heat to raise the temperature from 27.4*C to 67.3*C?
Q=418.6J
m=26.86g
delta t=t(final)-t(initial)
=67.3-27.4
=39.9*C
c=?

c=418.6J/(26.86g)(39.9*C)
c=0.391J/g*C
How it should look..
Final Temperature
If a 38g sample poof water releases 1621J of heat energy and cools to 34*C, what was the final temperature of water?
(specific heat of water=4.18J/g*C)
How it should look..
Q=-1621J
m=38g
c=4.18J/g*C
delta t=?

delta t= -1621J
38g(divided) 4.18J/g*C
=-10.2*C
Delta t=t(final)-t(initial)
34*C
-10.2*C
+ 34*C
23.8*C
Final Temperature
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