Kinetic Energy
• Energy an object possesses when in motion.
Law of Conservation of Energy
– in any physical or chemical change, energy
can change form, but the total amount of
energy remains constant.
HEAT
• Energy in a
system can be
transferred as
heat.
• Heat – the sum
total of kinetic
energy of the
particles in a
sample of
matter.
Temperature
• A measure of the
average kinetic
energy of particles in
a sample of matter.
• Temperature is used
to measure changes
in heat energy
Temperature Scales
• Temperature is commonly
measured using the Kelvin (K)
and the Celsius (oC) scales.
• To convert from one scale to
another, the following equations
can be used:
oC = K – 273
K = oC + 273
Specific Heat
• Not all substances will experience
the same changes in temp with
equal additions of heat energy.
This is due to a substance’s
specific heat capacity. (Cp)
• Cp – the amount of energy
required to raise the temp of 1
gram of a substance by 1 degree
Kelvin.
Specific Heat (Cp)
A substance’s specific heat can be
calculated using the following equation:
Cp = heat lost or gained (J or cal)
mass (g) x change in temp (K or oC)
***Note: The units for heat are Joules (J) or
the calorie (cal)
Specific Heat Problem
• In a lab experiment, 58.1 g of copper loses
1600.o J in cooling from 99.8°C to 28.4°C.
Calculate the specific heat.
Cp =
heat lost or gained (J or cal)
mass (g) x change in temp (K or °C)
• Cp = _____(1600.0 J)______
(58.1 g) x (99.8°C – 28.4°C)
• Cp = _____(1600.0 J)______
(58.1 g) x (71.4°C)
Cp = 0.386 J / g-°C
Specific Heat Practice Problem
• How much heat energy is required to raise the
temperature of 44.0 g of lead from 21°C to its
melting point, 327°C? The specific heat of
lead is 0.13 J/g-°C. Cp = heat lost or gained (J or cal)
mass (g) x change in temp (K or °C)
• Solve for heat energy
• 0.13 J/g-°C = _____[heat]______
(44.0g) x (327°C - 21°C)
• 0.13 J/g-°C = _____[heat]______
(44.0g) x (306°C)
Heat = (0.13 J/g-°C) x (44.0g) x (306°C)
Heat = 1750.32 J (**the g and °C cancel out!)
Temperature Practice!
1) Write down the two equations for converting
between Kelvin and Celsius.
Convert the following: Write problems and
answers for full credit!
2) 300 K = ______ºC
8) 0ºC = _______ K
3) 215 K = ______ºC
9) 173 K = ______ºC
4) 81 ºC = _____K
10) 84ºC = _______ K
5) 32 ºC = _____K
11) -20ºC = ______K
6) 0 K = ______ ºC
12) -100ºC = _____ K
7) 100 ºC = _____ K