Thermal Physics

Question 1

What is the definition of Mole in physics?

Answer 1

One mole of a substance is a quantity of a substance that contains a number of particles equal to the Avogadro constant ans whose mass in grams is equal to the molar mass of the substance

Question 2

What is the actual definition of mole in relation to Carbon-12?

Answer 2

One mole is defined to have as many number of particles as there are in 0.012 kg of an atom of Carbon-12

Question 3

What is the formula for calculating moles?

Answer 3

Number of Moles= Mass in grams/Molar mass in g/mol-1

Question 4

How to calculate the number of atoms in a substance?

Answer 4

The number of moles calculated multiplied to the Avogadro constant

Question 5

What is Pressure?

Answer 5

The normal force applied per unit area

Question 6

Why does the ideal gas model exist?

Answer 6

The ideal gas is a theoretical model of a gas that helps in understanding and predicting the behaviour of actual real gases

Question 7

What are the SIX assumptions made of ideal gases?

Answer 7

1. The molecules are point particles with negligible volume
2. The molecules obey the laws of mechanics
3. There are no forces between the molecules except when they collide with each other
4. The duration of a single collision is negligible compared to the time gap between several collisions taking place one after the other
5. The collisions between molecules and between molecules and walls of the container are elastic in nature
6. Molecules in an ideal gas have a range of speeds and move randomly

Question 8

What is the main difference between real gases and ideal gases? (intermolecular)

Answer 8

Ideal gases are said to have independently moving particles with no forces between each other unless contacted upon collision. However real gases have intermolecular forces even when there is no contact.

Question 9

How a real gas may be approximated by an ideal gas?

Answer 9

A real gas may be approximated by an ideal gas when the density is low

Question 10

What is the Boyle’s Law?

Answer 10

The Boyle’s law establishes the relationship between pressure and volume. At constant temperature and fixed quantity of gas, pressure is inversely proportional to volume.

Question 11

What is the equation/formula for Boyle’s law?

Answer 11

p1V1= p2V2

Question 12

What is the hyperbola curve in a pressure-volume diagram called in physics?

Answer 12

Isothermal curve or isotherm: in which the temperature at all points of the curve is the same

Question 13

What is the Charles’s law?

Answer 13

Charle’s law establishes the relationship between volume and temperature. Volume is directly proportional to temperature at constant pressure and fixed quantity of gas

Question 14

What is the nature of the plotted graph for Charles’ law?

Answer 14

The straight line of volume (Y-axis) against temperature (X-axis) when dotted backwards/extrapolated, it is seen that it always crosses the temperature axis at -273 celsius which is the lowest temperature and the absolute zero in the Kelvin scale

Question 15

What is the equation/formula of Charle’s law?

Answer 15

V/T= constant. V1/T1=V2/T2

Question 16

What is the Gay-Lussac’s law?

Answer 16

At constant volume and fixed quantity of gas, pressure increases uniformly with increasing temperature

Question 17

What is the equation for Gay-Lussac’s law?

Answer 17

p/T= constant. p1/T1= ps/T2

Question 18

What is the final equation of state also known as the ideal gas law equation?

Answer 18

pV= RnT
p= pressure
V= volume
R= universal gas constant
n= moles
T= temperature

Question 19

What is the relationship between the universal gas constant and number of moles?

Answer 19

The gas constant R is proportional to number of moles n

Question 20

What is the Boltzmann constant?

Answer 20

The ratio
R/NA (universal gas constant upon avogadro number)
is called the Boltzmann constant, kB