Thermal Physics Flashcards
temperature is the property, which determines _______ . It is a scalar quantity. The SI unit of temperature Figur is kelvin (K). There are other commonly used units of temperature such as degree celsius (°C) and degree fahrenheit (°F).
the direction of flow of heat.
The temperature measured in relation to absolute zero using the kelvin scale is known as _____. It is also known as the ______
absolute scale temperature
thermodynamic temperature
unit of the thermodynamic scale of temperature is defined as the ______ part of the thermodynamic temperature of the triple point of water.
fraction of 1/273.16th
A temperature difference of ______ is equal to that of 1K. Zero Kelvin is the absolute scale of temperature of the body.
1°C
Fahrenheit and Kelvin:
[K] = (F+460) ×(5/9)
Two or more physical systems or bodies are said to be in _________ if there is no net flow of thermal energy between the systems.
thermal equilibrium
When a hot object is in contact with another cold object, a form of energy flows from the hot object to the cold object, which is known as
thermal energy
Thermal energy is also known as ‘
heat energy’ or simply ‘heat’.
The SI unit of heat energy absorbed or evolved is
joule (J)
Characteristic features of heat energy transfer
- Heat always flows from a system at higher temperature to a system at lower temperature.
- The mass of a system is not altered when it is heated or cooled.
- For any exchange of heat, the heat gained by the cold system is equal to heat lost by the hot system.
Heat gained = Heat lost
Calorie:
One calorie is defined as the amount of heat energy required to rise the temperature of 1 gram of water through 1°C.
Kilocalorie:
One kilocalorie is defined as the amount of heat energy required to rise the temperature of 1 kilogram of water through 1°C.
Though the SI unit of heat energy is joule, there are some other commonly used units.
Calorie
Kilocalorie
When a certain amount of heat energy is given to a substance, it will undergo one or more of the following changes:
- Temperature of the substance rises.
- The substance may change its state from solid to liquid or from liquid to gas.
- The substance will expand when heated.
This change in the dimension due to rise in temperature is called
thermal expansion of the object
All forms of matter (solid, liquid and gas) undergo ____& on heating.
expansion
For a given change in temperature, the extent of expansion is smaller in solids than in liquids and gases. This is due to the _____.
rigid nature of solids
The different types of expansion of solid are listed and explained below:
- Linear expansion
- Superficial expansion
- Cubical expansion
linear or longitudinal expansion.
When a body is heated or cooled, the length of the body changes due to change in Its temperature. Then the expansion is said to be linear or longitudinal expansion.
coefficient of linear expansion
The ratio of increase in length of the body per degree rise in temperature to its unit length is called as the coefficient of linear expansion The SI unit of Coefficient of Linear expansion is K-¹
The equation relating the change in length and the change in temperature of a body is given below:
(∆L/L⁰)=aL ∆T
aL - alpha surfix L
superficial or areal expansion.
If there is an increase in the area of a solid object due to heating, then the expansion is called superficial or areal expansion.
coefficient of superficial expansion.
Superficial expansion is determined in terms of coefficient of superficial expansion. The ratio of increase in area of the body per degree rise in temperature to its unit area is called as coefficient of superficial expansion
(∆A/A⁰)=aA ∆T
cubical or volumetric expansion.
If there is an increase in the volume of a solid body due to heating, then the expansion is called cubical or volumetric expansion.
coefficient of cubical expansion
As in the cases of linear and areal expansion, cubical expansion is also expressed in terms of coefficient of cubical expansion. The ratio of increase in volume of the body per degree rise in temperature to its unit volume is called as coefficient of cubical expansion. This is also measured in K-¹
(∆v/v⁰)=av ∆T
Coefficient of cubic expansion (K-¹
Aluminium
7*10-⁵
Coefficient of cubic expansion (K-¹)
Brass
6*10-⁵
Coefficient of cubic expansion (K-¹)
Glass
2.5*10-⁵
Coefficient of cubic expansion (K-¹)
Water
20.7*10-⁵
Coefficient of cubic expansion (K-¹)
Mercury
18.2*10-⁵
The coefficient of cubical expansion of liquid is independent of temperature
whereas its value for gases depends on the temperature of gases
for liquids, we can define
real expansion and apparent expansion
_real expansion
If a liquid is heated directly without using any container, then the expansion that you observe is termed as real expansion of the liquid.
= L3-L2
Coefficient of real expansion
Coefficient of real expansion is defined as the ratio of the true rise in the volume of the liquid per degree rise in temperature to its unit volume. The SI unit of coefficient of real expansion is K-¹.
apparent expansion of the liquid.
The expansion of a liquid apparently observed without considering the expansion of the container is called the apparent expansion of the liquid.
L3-L1
Coefficient of apparent expansion
Coefficient of apparent expansion is defined as the ratio of the apparent rise in the volume of the liquid per degree rise in temperature to its unit volume. The SI unit of coefficient of apparent expansion is K-¹.
The three fundamental laws which connect the relation between pressure, volume temps and temperature are as follows:
1) Boyle’s Law
2) Charles’s law
3) Avogadro’s law
Boyle s law
When the temperature of a gas is kept constant, the volume of a fixed mass of gas is inversely proportional to its pressure.
Ρα 1/V
In other words, for an invariable mass of a perfect gas, at constant temperature, the product of its pressure and volume is a constant.
(i.e) PV constant
Charles’s law (The law of volume)
Charles’s law was formulated by a French scientist Jacques Charles. According to this law, When the pressure of gas is kept constant, the volume of a gas is directly proportional to the temperature of the gas.
V α T
or
V/T= constant
Avogadro’s law states ich that at constant pressure and he temperature, the volume of a gas is directly proportional to number of atoms or molecules present in it
i.e. Vαn (or) V /n = constant
Avogadro’s number
Avogadro’s number (NA) is the total number of atoms per mole of the substance. It is equal to 6.023 × 10²³/mol.
Gases are classified as
real gases and ideal gases.
real gases
If the molecules or atoms of a gases interact with each other with a definite amount of intermolecular or inter atomic force of attraction, then the gases are said to be real gases
At very high temperature or low pressure, a real gases behaves as an ideal gases
because in this condition there is no interatomicor intermolecular force of attraction.
If the atoms or molecules of a gas do not interact with each other, then the gas is said.to be an
ideal gas or a perfect gas.
Actually, in practice, no gas is ideal. The molecules of any gas will have a certain amount of interaction among them. But, these interactions are weaker when the pressure is low or the temperature is high because the interatomic or intermolecular forces of attraction are weak in ideal gas.
Hence, a real gas at low pressure or high temperature can be termed as a perfect gas.
The Boltzmann constant is defined to be exactly
1.380×10−23 J⋅K−¹.
term as universal gas constant
μNakB=R
8.31J mol-¹K-¹
Ideal gas equation is also called as equation of state
because it gives the relation between the state variables and it is used to describe the state of any gas.
Ideal gas equation, also called as equation of state is PV = RT. Here, R is known as universal gas constant whose value is
8.31 J mol-¹K-¹
A container whose capacity is 70 ml is filled with a liquid up to 50 ml. Then, the liquid in the container is heated. Initially, the level of the liquid falls from 50 ml to 48.5 ml. Then we heat more, the level of the liquid rises to 51.2 ml. Find the apparent and real expansion.
Level of the liquid L₁ = 50 ml
Level of the liquid L₂ = 48.5 ml
Level of the liquid L3 = 51.2 ml
Apparent expansion = L3 - L₁
= 51.2 ml-50 ml = 1.2ml
Real expansion = L3 - L₂
= 51.2 ml - 48.5ml = 2.7ml
So, Real expansion > apparent expansion
Keeping the temperature as constant, a gas is compressed four times of its initial pressure. The volume of gas in the container changing from 20cc ({V1 cc) to V2} . Find the final volume V2
P1V1=P2V2
V2=(P1/P2)V1
(P/4P)20 Cm³
V2= 5cm³
If a substance is heated or cooled, the change in mass of that substance is
a) positive
b) negative
c) zero
d) none of the above
Zero
If a substance is heated or cooled, the linear expansion occurs along the axis of
a) X or -X
b) Y or -Y
c) both (a) and (b) d)(a) or (b)
Both a and b
Temperature is the average of the molecules of a substance
a) difference in K.E and P.E
b) sum of P.E and K.E
c) difference in T.E and P.E
d) difference in K.E and T.E
difference in T.E and P.E
The temperature and heat are _______quantities
Scalar
- One calorie is the amount of heat energy required to raise the temperature of ____of water through____
1g
1k
- According to Boyle’s law, the shape of the graph between pressure and reciprocal of volume is ______
Straight line
For a given heat in liquid, the apparent expansion is more than that of real expansion
Flase
According to Charles’s law, at constant pressure, the temperature is inversely proportional to volume.
Flase
the temperature is directly proportional to volume.
Assertion: There is no effects on other end when one end of the rod is only heated.
Reason: Heat always flows from a region of lower temperature to higher temperature of the rod.
Assertion is true but the reason is false.
- Assertion: Gas is highly compressible than solid and liquid
Reason: Interatomic or intermolecular distance in the gas is comparably high
Both the assertion and the reason are true and the reason is the correct explanation of the assertion.
Find the final temperature of a copper rod. Whose area of cross section changes from 10m² to 11 m² due to heating. The copper rod is initially kept at 90 K. (Coefficient of superficial expansion is 0.0021 /K)
T = 137.62K
Calculate the coefficient of cubical expansion of a zinc bar. Whose volume is increased 0.25 m³ from 0.3 m³ due to the 3 change in its temperature of 50 Κ.
α = 1.111×10^-3 /K.
If you keep ice at 0°C and water at 0°C either of your hands, in which hand you will feel more chillness? Why?
Because water has the hidden heat called latent heat
Reason: The 0°C ice takes more heat from hand equal to mL, to convert 0°C Ice water, 0°C as compared to 0°C water of same mass.
