Transcript Temperature and Heat

Match the different types of energy transformation in
each picture.
IRON
a.
WINDMILL
b.
1. Electrical to Mechanical
2. Nuclear to Thermal
3. Mechanical to Electrical
4. Electrical to Thermal
MIXER
c.
___________
___________
___________
___________
SUN
d.
Temperature is the measure of the average
kinetic energy of the particles of matter. You need
a thermometer to measure temperature.
There are three types of temperature scales:



Fahrenheit (F)
Celsius (C)
Kelvin (K).
Although the Fahrenheit scale is widely used,
the Celsius scale is more compatible with
temperature measurements used in the metric
system. Even though the Fahrenheit and
Celsius temperature scales are extremely useful
for various applications, the Kelvin scale is used
to measure temperature in the International
System of Units (SI).
The difference between the Kelvin and Celsius
scales is the location of the zero point. The zero
point of the Kelvin scale (0K), called absolute
zero, corresponds to -273C. Absolute zero is
the point at which the motion of particles of
matter ceases.
Conversions between these two scales can be
made by using the following formulas:
C + 273 = K
K – 273 = C.
Heat is defined as the transfer of kinetic energy
from a hotter object to a colder object. Heat is
measured in units of joules or calories.

A hot drink left in a cold place will always lose
heat to the surroundings. It will get cooler until
eventually it is at the same temperature as its
surroundings. But if it is inside a good thermal
insulator (such as a thermos flask), it will lose
the heat very slowly.
Reactions that release heat to its surroundings
are called exothermic reactions. When an
exothermic reaction releases heat to its
surroundings, the temperature of the
surroundings increases.
Reactions that absorb heat are called
endothermic reactions. When an endothermic
reaction absorbs heat, the temperature of its
surroundings decreases.
The size of the temperature increase depends
on how much heat is released and on the heat
capacity of the surroundings. The heat capacity of
an object is the amount of heat needed to raise the
temperature of the object by 1 Celsius degree. The
heat capacity of an object depends on its mass and
its composition. A large mass of water can absorb a
large quantity of heat with only a small
temperature increase.
The heat capacity of 1 gram of a substance is
called its specific heat. The specific heat is a
physical property of the substance like its color
and melting point. Different substances have
different capacities for storing energies.
SPECIFIC HEAT OF SOME SUBSTANCES
Substance
H2O (l)
H2O (s)
Al (s)
C (s)
Fe (s)
Hg (s)
Specific Heat (J/g C)
4.184
2.03
0.89
0.71
0.45
0.14
The amount of heat given off or absorbed can
be calculated by the following formula:
(Tf - Ti)
Q = m x T x Csp
Q = heat (measured in Joules (J) or calories (cal))
m = mass (g)
T = change in temperature (T = final temperature (T ) – initial temperature (T ))
Csp = specific heat (J/gC or cal/gC)
f
i
If the specific heat of water is 4.184 J/gC,
how much heat must be added to 5 g of
aluminum to raise its temperature by 2 Celsius
degrees?
Q = m x T x Csp
1.
Q =
m=
T =
Csp =
2. The specific heat of aluminum is 0.89 J/g  C.
How much heat is required to raise the
temperature if 16 grams of aluminum from
25C to 75C?
Q = m x T x Csp
Q =
m=
T =
Csp =
1.
A sample of KCl dissolves in 75g of H2O. The
temperature changes from 21.6°C to 31°C.
How much heat was exchanged?
(Csp of water = 4.184 J/g°C or 1 cal/g°C)
Q =
m=
T=
Csp =
2.
What is the specific heat of aluminum if the
temperature of a 28.4g sample of aluminum is
increased by 8.1C when 207 J of heat is
added?
Q = m x T x Csp
Q =
m=
T =
Csp =