Thermodynamics (9)

Question 1

What is the definition of specific heat capacity?

Answer 1

The energy required to raise the temperature of one kilogram of a substance by one kelvin.

Question 2

What three factors determine the increase in temperature of an object?

Answer 2

The amount of heat energy transferred, the mass of the object, and the specific heat capacity of the material.

Question 3

What is the formula for calculating heat energy transfer?

Answer 3

ΔE = mcΔθ

Question 4

what does θ represent in the specific heat capacity equation

Answer 4

Temperature change (K)

Question 5

Why do different materials have different specific heat capacities?

Answer 5

Due to differences in their molecular structure.

Question 6

Why is copper a good conductor of heat?

Answer 6

Because it has a low specific heat capacity, allowing it to heat up and cool down quickly.

Question 7

Why is water ideal for heating homes?

Answer 7

It has a high specific heat capacity, meaning it retains heat for a long time.

Question 8

What happens to energy when a substance changes state?

Answer 8

Energy is required, but there is no change in temperature.

Question 9

What is latent heat?

Answer 9

The thermal energy required to change the state of one kilogram of a substance without changing its temperature.

Question 10

What are the two types of latent heat?

Answer 10

Specific latent heat of fusion (melting) and specific latent heat of vaporisation (boiling).

Question 11

What is the specific latent heat of fusion?

Answer 11

The energy required to convert one kilogram of solid to liquid with no temperature change.

Question 12

What is the specific latent heat of vaporisation?

Answer 12

The energy required to convert one kilogram of liquid to gas with no temperature change.

Question 13

What is the equation for calculating latent heat?

Answer 13

Amount of energy needed to change state=latent heat of fusion or vaporisation * change in mass

Question 14

Why does vaporising water require more energy than melting ice?

Answer 14

Because breaking all inter-molecular forces in boiling requires much more energy than just increasing molecular separation in melting.

Question 15

What are the two forms of energy?

Answer 15

Kinetic energy and potential energy.

Question 16

How do kinetic and potential energy relate to molecules?

Answer 16

Kinetic energy is due to the speed of molecules and determines temperature, while potential energy is due to molecular separation and position.

Question 17

What determines the amount of kinetic and potential energy a substance has?

Answer 17

Its phase of matter (solid, liquid, or gas).

Question 18

How is internal energy defined?

Answer 18

The sum of the kinetic and potential energies of all molecules within a given mass of a substance.

Question 19

Which phase of matter has the highest internal energy? Which has the lowest?

Answer 19

Gases have the highest internal energy, while solids have the lowest.

Question 20

What is absolute zero?

Answer 20

The lowest possible temperature, equal to 0 K or -273.15°C, where molecules have zero kinetic energy.

Question 21

Can a temperature be lower than 0 K?

Answer 21

No, it is not possible to have a temperature lower than absolute zero, meaning Kelvin temperatures are never negative.

Question 22

What happens to molecules at absolute zero?

Answer 22

They have zero kinetic energy, meaning no more energy can be removed from the system.

Question 23

How does kinetic energy relate to temperature in different states of matter?

Answer 23

In solids, molecules vibrate; in gases, they move quickly around their container.

Question 24

Has absolute zero ever been reached?

Answer 24

No, it remains a theoretical point that has never been achieved in a laboratory.

Question 25

What does the kinetic theory of gases describe?

Answer 25

It models the thermodynamic behavior of gases by linking microscopic properties (mass and speed) to macroscopic properties (pressure and volume).

Question 26

What are the key assumptions of the kinetic theory of gases?

Answer 26

1. Gas molecules are identical, hard, 2. perfectly elastic spheres 3. with negligible volume, 4. no intermolecular forces, 5. and are in continuous random motion.

Question 27

Why is the volume of gas molecules considered negligible?

Answer 27

Because the size of the molecules is extremely small compared to the total volume of the container.

Question 28

Why are intermolecular forces ignored in the kinetic theory of gases?

Answer 28

The theory assumes there are no forces of attraction or repulsion between gas molecules.

Question 29

What is mean square speed in the context of gases?

Answer 29

The mean square speed, , is the average of the squared velocities of gas molecules and has units of m²/s².

Question 30

Why do we square the velocities when calculating mean square speed?

Answer 30

Because velocity is a vector, squaring ensures all values are positive, preventing them from canceling out.

Question 31

What is the root-mean-square (r.m.s) speed?

Answer 31

It is the square root of the mean square speed, representing the average speed of gas particles.

Question 32

When pressure is high, is volume high or low

Answer 32

low

Question 33

Relationship between 2 gasses and 2 volumes

Answer 33

P1*V1=P2*V2

Question 34

Is volume directly proportional to temp

Answer 34

yes

Question 35

Is pressure directly proportional to temp

Answer 35

Yes

Question 36

What is black body radiation?

Answer 36

The thermal radiation emitted by all objects in the form of electromagnetic waves.

Question 37

In which part of the spectrum does black body radiation usually lie?

Answer 37

Mostly in the infrared region, but it can also include visible light or other wavelengths depending on temperature.

Question 38

How does temperature affect black body radiation?

Answer 38

Hotter objects emit more infrared radiation in a given time and at shorter wavelengths.

Question 39

What is a perfect black body?

Answer 39

An object that absorbs (or emits) all radiation incident on it and does not reflect or transmit any radiation.

Question 40

Why does a perfect black body appear black?

Answer 40

It absorbs all visible light, meaning no colors are reflected back to the observer.

Question 41

How does temperature affect the black body radiation curve?

Answer 41

As temperature increases, the peak of the curve moves to shorter wavelengths.

Question 42

What kind of electromagnetic waves have the highest energy?

Answer 42

Waves with shorter wavelengths, such as UV rays and X-rays.

Question 43

What is the best real-world approximation of a black body?

Answer 43

Stars, as they emit radiation according to their temperature.

Question 44

What is Stefan-Boltzmann Law

Answer 44

The total energy emitted by a black body per unit area per second is proportional to the fourth power of the absolute temperature of the body

Question 45

What does Stefan-Boltzmann Law mean

Answer 45

Luminosity is directly proportional to the surface area of a star * Surface temp of the star to the 4th power

Question 46

What is luminosity sometimes called

Answer 46

PowerW

Question 47

What is Wien's law

Answer 47

The black body radiation curve for different temperatures peaks at a wavelength that is inversely proportional to the temperature

Question 48

What is the equation linked to Wien's law

Answer 48

llamda max is inversely proportional to temperature

Question 49

What does Wien's law tell us when temp is higher

Answer 49

1. At peak intensity, wavelength is lower 2. Greater intensity of radiation at each wavelength

Question 50

What colour do hot stars appear as, and why

Answer 50

White/blue, as wavelength is lower when temp increases