The document discusses quantities of heat. It defines heat as the energy transfer due to temperature differences. The common units of heat are joules (J) and calories (cal). A calorie is the amount of heat needed to raise 1 gram of water by 1°C. The formula to calculate the quantity of heat (Q) transferred is Q = mCΔT, where m is the mass, C is the specific heat capacity, and ΔT is the temperature change. The example problem calculates the heat required to increase the temperature of 450 grams of water by 70°C using the specific heat of water.

1. QUANTITIES OF
HEAT

2.  The quantity of heat is a measurement of the
amount of heat is present.
The unit of heat is defined as the heat
necessary to produce some standard, agreed
upon temperature change for a specificied
amount of amaterial.
 Calorie- the amount of heat necessary to taise
1 gram of water by 1 degree Celcius
 1 kilocalorie= 1000 calories= 1 Calorie
 In SI System 1 calorie = 4.187 J

3. Quantities of Heat
Quantity Symbol Unit Meaning
heat Ǫ
joule (J) SI unit
calorie(cal)
Energy transfer that produces
or results from a difference in
temperature.
temperature T oC or K
Measure of the kinetic
energy of molecular motion.
temperature
change ΔT oC or K
Difference between the final
and initial temperatures for a
process.
heat capacity C
JoC-1 orJK-1
cal oC-1
Heat required to change the
temperature of a substance
one degree.

4. Relating the Quantity of Heat to
the Temperature Change
Specific heat capacities provide a
means of mathematically relating the
amount of thermal energy gained (or
lost) by a sample of any substance to
the sample's mass and its resulting
temperature change.

5.  The formula of quantity of heat is:
Q = m•C•ΔT
 Q is the quantity of heat transferred to or
from the object
 m is the mass of the object
C is the specific heat capacity of the material
 ΔT is the resulting temperature change of
the object

6. • As in all situations in science, a delta (∆) value for
any quantity is calculated by subtracting the initial
value of the quantity from the final value of the
quantity. In this case, ΔT is equal to Tfinal -
Tinitial. When using the above equation, the Q
value can turn out to be either positive or negative.
As always, a positive and a negative result from a
calculation has physical significance. A positive Q
value indicates that the object gained thermal
energy from its surroundings; this would
correspond to an increase in temperature and a
positive ΔT value. A negative Q value indicates
that the object released thermal energy to its
surroundings; this would correspond to a decrease
in temperature and a negative ΔT value.

7. Example Problem 1
What quantity of heat is required to raise the temperature
of 450 grams of water from 15°C to 85°C? The
specific heat capacity of water is 4.18 J/g/°C.
GIVEN
• m = 450 g
• C = 4.18 J/g/°C
• Tinitial = 15°C
• Tfinal = 85°C

8.  FIND= ΔT?
 We wish to determine the value of Q - the quantity of heat. To do so,
we would use the equation Q = m•C•ΔT. The m and the C are
known; the ΔT can be determined from the initial and final
temperature.
(1)
ΔT = Tfinal - Tinitial = 85°C - 15°C = 70.°C
 SOLUTION
With three of the four quantities of the relevant equation known, we
can substitute and solve for Q.
• Q = m•C•ΔT = (450 g)•(4.18 J/g/°C)•(70.°C)
• Q = 131670 J
• Q = 1.3x105 J = 130 kJ (rounded to two significant digits)

9. Thank You