Chapter 14 - Thermal physics

Question 1

what is triple point?

Answer 1

specific temperature at which three phases of a substance can exist in thermal equilibrium.

Question 2

what is the zeroth law of thermodynamics?

Answer 2

-it states that if 2 objects are in thermal equilibrium with a third, then all 3 are in thermal equilibrium with each other.

Question 3

explain the arrangement in solids?

Answer 3

-in solid the particles are regularly arranged and packed closely together, with strong electrostatic forces of attraction between them in fixed positions, but they can vibrate and so have kinetic energy

Question 4

explain the arrangement in liquids?

Answer 4

-particles are close together, but they have more kinetic energy than in solids and are also able to flow past each other.

Question 5

explain the arrangement in gases?

Answer 5

• the particles have more kinetic energy than liquids as they are further apart. they are free to move past each other as there are negligible electrostatic forces between them, unless they collide

Question 6

how does brownian motion give evidence for the particle model of matter?

Answer 6

-smoke particles suspended in air can be seen to move randomly in all directions. this must be as a result of random collisions with particles making up the air.

Question 7

what is internal energy?

Answer 7

• sum of randomly distributed kinetic and potential energies of particles within a substance

Question 8

what is it the specific heat capacity of a substance?

Answer 8

the energy required per unit mass to change the temperature by 1 K.

Question 9

Describe the electrostatic potential energy in gas atoms?

Answer 9

-its zero because there are negligible electrical forces between atoms

Question 10

Describe the electrostatic potential energy in liquid atoms?

Answer 10

-the electrostatic forces between atoms give the electrostatic potential energy a negative value. the negative means that energy must be supplied in order to break the bonds.

Question 11

describe the electrostatic potential energy in solid atoms?

Answer 11

the electrostatic forces between atoms are very large so the electrostatic potential energy has a large negative value.

Question 12

state two ways to increase the internal energy of a substance?

Answer 12

• increase the temperature of the substance

- change the phase of the substance from solid to liquid or from liquid to gas.

Question 13

explain in terms of internal energy, why a window gets slightly warmer when water vapour condenses on its surface?

Answer 13

-when water vapour condenses there is a decrease in electrostatic potential energy of the particles in the water as the energy is transferred from the water to the window.

Question 14

definition of specific heat capacity?

Answer 14

-energy required per unit mass to change the temperature by 1 K

Question 15

definition of specific latent heat of fusion?

Answer 15

-energy needed to melt a unit mass of a solid at its melting temperature without changing the temperature.

Question 16

what is absolute zero? definition?

Answer 16

-the theoretical lowest possible temperature at which a point a body would have no internal energy and its particles would have no kinetic energy.

Question 17

Describe the experiment to find the specific heat capacity of water using a heater?

Answer 17

-diagram
-insert a thermometer and the immersion heater into the block.
-write down initial temperature
-setup a suitable circuit
-turn on the current and measure the time so that you can measure the energy
-measure voltmeter and ammeter reading
Energy = IVt
-allow block to heat up by 10 K turn of current and stop the time
-record the final temperature
Use E=mct to find specific heat capacity of the block