Bahasa Inggris untuk Fisika

1. TEMPERATURE AND
MEASURING HEAT
DESVITA ROZA

2. Temperature
Temperature and Gas Laws
 Heat is a form of energy and when heat is supplied to an
object it increases the internal energy of the object
 The internal energy of an object is made up of the kinetic
end potential energies of its atoms and molecules
 Atom and molecules have kinetic energy because of their
vibrational, rotational, and translational motions
 Potential energy of atoms and molecules are associated
with their relative states or positions
 Potential energy of a system is greater when objecta are
father apart

3. Temperature
 When heat energy is supplied to an object,
its temperature rises
 The rise in temperature is purely due the
increase in the translational kinetic energy
of the molecules of the object
If the same quantity of heat is supplied
to different quantities of water, their
increase in temperature will not be the
same despite the fact that the total
increase in kinetic energy is the same
in all cases

4.  The larger quantity will have a smaller
increase in temperature while the
smaller quantity will have a larger
increase in temperature
 In case of the larger quantity, more
number of molecules share the
additional energy, while in the case of
the smaller quantity, less number of
molecules share the same increase
and so the increase in kinetic energy
per molecule will be larger in the
smaller mass
 Temperature of an object is
proportional to the average kinetic
energy of its molecules.

5. Measuring Temperature
 In order to measure temperature, we make use of properties
of materials that change with temperature.
 For example, most subtance expand when heated, and the
increase in volume is very nearly proportional to the change
in temperature
 Therefore, the increase in volume of a substance can be
used to measure temperature

 Mercury or alcohol in glass
 thermometer is an exampe of this

6. Temperature Scales
 There are two main scales of temperature used
in measuring temperature
 One scale called the Celcius scale uses an
arbitrary temperature, namely the temperature
at which ice melts at atmospheric pressure, as
its zero
 The other scale called the Kelvin scale uses
the temperature at which the molecular energy
is zero as its zero
 In the celcius scale, temperature is measured
in a unit called degree Celcius (oC), while in
Kelvin scale the unit temperature is a Kelvin(K)

7.  We use t to represent temperature in
Celcius scale and T for temperature in
Kelvin scale.
 A relation between T and t is given by :
T K = toC + 273,15
0oC = 273,15 K
 The temperature at which water boils at
atmospheric pressure is 100oC =373,15
K

8. Mercury in glass thermometer
 Mercury thermometer used in the laboratory are marked
in degree Celsius and used the property of expansion of
mercury with temperature
 The length of mercury column in the stem of the
thermometer varies linearly with the temperature of the
mercury in the bulb
 Two fixed points are marked on the stem
 The lower fixed point corresponds to the temperature of
melting ice at atmospheric pressure and the upper fixed
point corresponds to temperature of boiling water at
atmospheric pressure
 The interval between these two fixed points is divided
into 100 equal parts

9. Constant volume gas
thermometer
 The pressure of a fixed mass of gas
enclosed at constant volume changes
linearly with temperature
 The pressure of the gas enclosed in
the bulb can be measured by keeping
its volume always the same by using a
mercury manometer

10. Triple point temperature
 The ice point and steam point are not very easily
reproducible all the time
 A reference point which is more precisely
reproducible than the ice point and the steam is the
tripple point of water
 The tripple point is the unique temperature and
pressure at which water, water vapoor and ice will
coexist in equilibrium
 The ideal gas temperature scale is defined such that
the temperature of the triple point is 273,16 K
 The temperature of any other state is then
proportional to the pressure in the constant volume
thermometer

11. Measuring Heat
 Heat capacity and specific heat
 Specific heat of a substance is the amount of
heat needed to raise temperature of 1 kg of a
substance by 1K .
 Spesific heat measured in J.Kg-1 .K-1 and is
represented by c.
 4180 J of heat energy is required to raise the
temperature of 1 Kg of water by 1 K.
 390 J of heat energy is required to raise the
temperature of 1 Kg of copper by 1 K.
 Spesific heat of copper 390 J.Kg-1 K-1

12.  The quantity of heat Q required to raise the temperature of
m Kg of a substance from an initial temperature θ1 to a final
temperature θ2 is given by:
 Q = m c Δθ Δθ = θ2- θ1
 Heat capacity of an object is the amount of heat needed to
raise the temperature of the object by 1 K.
 Heat capacity is measured in JK-1 an is represented by C.
 If m is the mass of an object then the heat capacity of that
object is :
 C = m c
 Molar heat capacity (Cm) is the amount of heat required to
raise the temperature of 1 mole of a substance by 1 K.
 Molar heat capacity is measured in J mol-1K-1.

13. Latent Heat and Change of State
 When heat is supply to a solid, the vibrational kinetic energy
of it molecules in increas, and hence the temperature of the
solid increases.
 This continues until the solid reaches its melting point and
any additional heat added does not increase the kinetic
energy of the molecules, instead it is used to overcome the
intermolecular forces to free molecules from one another so
that they are free to move about.
 During this change of state, the molecules do not speed up,
but the extra energy given is used in gaining potential energy.
 When heat is supplied to a liquid, the translational kinetic
energy of its molecules increas, and its temperature
increase.

14.  This continues until the liquid reaches its bolling point and
any additional heat added does not increase the kinetic
energy of the molecules,instead it is used to evercome the
intermolecular forces to free molecules from one another
so that they are free to escape the liquid.
 This is the time when a liquid turns into a gas of vapor.
 During this change of state, the molecules do not speed
up, but the extra energy given is used in gaining potential
energy.
 When a vapor condenses back to liquid, heat energy is
given out, but it does not lower the temperature because it
is the potential energy that lost and not kinetic energy.
 Since the amount of heat absorbed or liberated during a
change of state does not manifest in a change the
temperature, this heat is called the latent (hidden) heat.
 We use L to represent latent heat and it is measured in
J.Kg-1

15.  Specific latent heat of fusion of a substance is a measure of
the amount of heat absorbed or liberated by 1 Kg of a
substance at its melting point to convert either from a solid to
liquid or from a liquid to solid without a change in temperature.
 We use L, to represent latent heat of fusion and it is measured
in J.Kg-1
 For water, Lf = 333.5 kJ Kg-1 = 3.34 x 103 J.Kg-1
 Spesific latent heat of vaporization (Lv) of a substance is a
measure of the amount of heat absorbed of liberated by 1 kg of
a substance at its boilling point to convert either from liquid to
vapor or from vapor to liquid without causing a change in
temperature.
 For water, Lv = 2257 kJ kg-1 = 2.26 x 106 J kg-1
 The amount of heat Q required to convert m kg of a solid at its
melting point to liquid at the same temperature is : Q = m Lf
 The amount of heat Q required to convert m kg of a liquid at
its boilling point to vapor at the same temperature is : Q = m Lv

16. • Let us heat 1 kg of ice at -50oC until it
becomes steam at 100oC
• As heat is supplied to it, its temperature
increases to 0oC
• Q1 = m c Δθ
= 1 kg x 4180 J Kg-1 K-1 x 50 K
= 2.09 x 105 J
• As further heat is supplied, ice at 0oC
changes to water at 0oC
• Q2 = m Lf
= 1 Kg x 3.34 x 10-5 J kg-1
= 3.34 x 105 J

17. • Once all the ice is melted, the temperature
rises until it reaches the boiling point,
100oC.
• Q3 = m c Δθ
= 1 kg x 4180 J kg-1 K-1 x 100 K
= 4.18 x 105 J
• As further heat is supplied, water at 100oC
changes to steam at 100oC
• Q4 = m Lv = 1 kg x 2.26 x 106 J kg-1 = 2.26 x
106 J
• Total heat = Q1 + Q2 +Q3 +Q4
= 3.22 x 106 J

18. Thank you for your
attention

19. Istilah istilah fisika
Kinetic end potential
energies
Vibrational, rotational, and
translational motions
Relative states
Temperature rises
Additional energy
 Measuring Temperature
Celcius
At atmospheric pressure
Equilibrium
Molar heat capacity
To raise the temperature
Heat capacity
The translational kinetic
energy
Specific latent heat of
fusion
Mercury in glass thermometer