1. 5. TEMPERATURE AND HEAT, IDEAL GASES
DEC 1013
ENGINEERING SCIENCEs
5. TEMPERATURE AND HEAT, IDEAL GASES
NAZARIN B. NORDIN

2. What you will learn: Heat and temperature Temperature scales
Conversion between scales
Transfer of heat: conduction, convection, radiation
Heat capacity: specific heat capacity and latent heat (latent heat of fusion ; latent heat of vaporization)
Phases of matter (solid, liquid, gas)

3. Temperature
The energy transferred from a high-temperature object to a lower-temperature object is called heat.
Celsius, Fahrenheit, Kelvin.
((C*9)/5)+32=f
((F-32)*5)/9=c
C =k
The specific heat capacity of a solid or liquid is defined as the heat required to raise unit mass of substance by one degree of temperature.

4. Temperature scale the SI
unit of temperature, the kelvin, is defined as 1/ of the temperature of the
triple point of water.
the
triple point of water, which is the single temperature and pressure at which water,
water vapor, and ice can coexist in equilibrium.
it occurs at a temperature of 0.01C and a pressure of 4.58 mm of mercury.

5. Conversion between scales

6. Scale conversion

8. Conduction Thermal Conduction
The energy transfer process most closely associated with a temperature
difference is called thermal conduction or simply conduction. In this process, the
transfer can be viewed on an atomic scale as an exchange of kinetic energy
between microscopic particles—molecules, atoms, and electrons—with less energetic
particles gaining energy as they collide with more energetic particles.

11. Convection
The transfer of energy by the movement of a substance is called convection.

12. Radiation

15. Heat
Early in the development of thermodynamics, before scientists realized the connection
between thermodynamics and mechanics, heat was defined in terms of the
temperature changes it produced in an object, and a separate unit of energy, the
calorie, was used for heat. The calorie (cal) is defined as the energy necessary to
raise the temperature of 1 g of water from 14.5° to 15.5°C.
Likewise, the unit of heat in the U.S. customary system, the British thermal
unit (Btu), was defined as the energy required to raise the temperature of 1 lb of
water from 63°F to 64°F.

16. Sensible heat
The specific heat capacity of a solid or liquid is defined as the heat required to raise unit mass of substance by one degree of temperature.

17. Remarks
Notice the use of 2.01 m in the denominator of the last calculation, rather than 2.00 m. This is because, in
effect, the strut was compressed back to the original length from the length to which it would have expanded. (The difference
is negligible, however.) The answer exceeds the ultimate compressive strength of steel and underscores the importance
of allowing for thermal expansion. Of course, it’s likely the strut would bend, relieving some of the stress
(creating some shear stress in the process). Finally, if the strut is attached at both ends by bolts, thermal expansion
and contraction would exert sheer stresses on the bolts, possibly weakening or loosening them over time.

22. Latent heat
The unit of latent heat is the joule per kilogram ( J/kg). The word latent means “lying
hidden within a person or thing.” The positive sign in Equation 11.6 is chosen when
energy is absorbed by a substance, as when ice is melting. The negative sign is chosen
when energy is removed from a substance, as when steam condenses to water.
The latent heat of fusion Lf is used when a phase change occurs during melting
or freezing, while the latent heat of vaporization Lv is used when a phase change
occurs during boiling or condensing.
For example, at atmospheric pressure the latent heat of fusion for water is J/kg, and the latent heat of vaporization for water is J/kg. The latent heats of different substances vary considerably,
as can be seen in Table 11.2.
Another process, sublimation, is the passage from the solid to the gaseous phase
without going through a liquid phase. The fuming of dry ice (frozen carbon dioxide)
illustrates this process, which has its own latent heat associated with it—the
heat of sublimation.

23. To better understand the physics of phase changes, consider the addition of
energy to a 1.00-g cube of ice at 30.0°C in a container held at constant pressure.
Suppose this input of energy turns the ice to steam (water vapor) at 120.0°C.
Figure 11.3 is a plot of the experimental measurement of temperature as energy is
added to the system. We examine each portion of the curve separately.

24. Phase changes can be described in terms of rearrangements of molecules when
energy is added to or removed from a substance. Consider first the liquid-to-gas
phase change. The molecules in a liquid are close together, and the forces between
them are stronger than the forces between the more widely separated molecules
of a gas. Work must therefore be done on the liquid against these attractive
molecular forces in order to separate the molecules. The latent heat of vaporization
is the amount of energy that must be added to the one kilogram of liquid to
accomplish this separation.
Similarly, at the melting point of a solid, the amplitude of vibration of the atoms
about their equilibrium positions becomes great enough to allow the atoms to pass
the barriers of adjacent atoms and move to their new positions. On average, these
new positions are less symmetrical than the old ones and therefore have higher energy.
The latent heat of fusion is equal to the work required at the molecular level
to transform the mass from the ordered solid phase to the disordered liquid phase.
The average distance between atoms is much greater in the gas phase than in
either the liquid or the solid phase. Each atom or molecule is removed from its
neighbors, overcoming the attractive forces of nearby neighbors. Therefore, more
work is required at the molecular level to vaporize a given mass of a substance
than to melt it, so in general the latent heat of vaporization is much greater than
the latent heat of fusion (Table 11.2).

31. Basic structure of solids, liquids and gases
The hotter they are, the faster they move.
This can explain freezing/melting, boiling/condensing and lots more.
It is called the Kinetic Theory of Matter. Kinetic is something to do with movement.
Solid
Liquid
Gases
Heater

32. Basic structure of solids, liquids and gases

33. Basic structure of solids, liquids and gases

34. Basic structure of solids, liquids and gases

35. Basic structure of solids, liquids and gases

36. THANK YOU