2. Matter and Energy

Physical States of Matter
Solid (s)
Liquid (l)
Gas (g)
Aqueous (aq)
*must know how to define them using
shape and volume.
Techniques for Separating Mixtures
EXOTHERMIC: energy is given off in a
chemical reaction.
A+B  C + Heat
ENDOTHERMIC: energy is absorbed in a
chemical reaction.
Heat + A  B+C
Entropy: A measure of the disorder of a
system. The more disorder, the more
Potential Energy (PE): Stored energy.
Kinetic Energy (KE): Energy of movement.
Energy is transferred from one form to
Potential Energy
Kinetic Energy
Heat Flow
Whenever two objects with different temps are in
contact, heat travels from higher temperature to lower
temperature until both temps are the same
If you have a cup of milk at 80°C and a cup at 20°C and
you mix the two cups together, heat would flow from the
cup of milk at 80°C to the cup of milk at 20°C until both
cups are at the same temp, around 50°C
REMEMBER: To convert Kelvin to Celsius or Celsius to
Kelvin use the following formula:
K = °C + 273
Heating/Cooling Curve
(must be able to label the entire graph & label PE & KE changes)
Heat Equations: (Table T)
q = mC∆T
q = mHf
q = mHv
q = Heat (in joules)
m = Mass (in grams)
C = Specific Heat Capacity (Table B): the amount of heat
required to raise 1 gram of something 1 degree Celsius (ex:
4.18 joules/g°C)
T = Change in temperature (Final - Initial)
– If q is negative: exothermic reaction (release heat)
– If q is positive: endothermic reaction (absorb heat)
Hf = Heat of fusion (energy required to freeze/melt)
Hv = Heat of vaporization (energy required to
Table B represents physical constants for
water only. If a heat equation question is
asking about anything other than water,
the constant for the substance will have to
be provided (C, Hf,Hv).
The plateau for vaporization/condensation
is longer than melting/freezing because the
Hv is greater than the Hf, and therefore it
takes longer to add or release heat.
When 20.0g of a substance is completely melted at its melting point,
3444 J are absorbed. What is the heat of fusion of this substance?
The heat of vaporization of a liquid is 1344 J/g. What is the minimum
number of joules needed to change 40.0g of the liquid to vapor at the
boiling point?
How much energy is required to vaporize 10.00g of water at is boiling
At 1 atmosphere of pressure, 25.0g of a compound at its normal boiling
point is converted to a gas by the addition of 34,400 J. What is the
heat of vaporization for this compound in J/g?
The heat of fusion of a compound is 30.0 joules per gram. What is the
number of joules of heat that must be absorbed by a 15.0g sample to
change the compound from solid to liquid at its melting point?