Thermal Physics 5.1

Question 1

What is temperature?

Answer 1

-A measure of how hot or cold an object is. It is a measure of the kinetic energy of an objects total internal energy.

Question 2

What is the absolute scale of temperature?

Answer 2

-A scale of temperature which isn’t dependant on any physical properties and starts at absolute zero

Question 3

What is absolute zero and the triple point of water?

Answer 3

-The temperature at which particles of matter have minimum internal energy
-The value of absolute zero(0 kelvin) is -273.16 degrees Celsius
-The triple point of water is the point at which solid, liquid and gas particles of water exist simultaneously which is 273.16K

Question 4

What is thermal equilibrium?

Answer 4

-The point at which objects in contact with each other are at the same temperature, so no net heat flow

Question 5

A small block of aluminium with an initial temperature of 75 degrees celcius is placed in a bath tub full of water at 15 degrees Celsius suggest the temperature of thermal equilibrium and why?

Answer 5

-Around 20-25 degrees Celsius
-The water is very large in comparison to the aluminium block so the aluminium block has small thermal energy store therefore it can only transfer a small amount of energy to the water and the temperature of the water won’t increase by much

Question 5

Describe using the kinetic model of matter how the particles are in solids?

Answer 5

-Close together due to their strong forces of attraction and vibrate about their individual fixed positions
-Generally have a high density and definite shape

Question 6

Describe using the kinetic model of matter how the particles are in liquids?

Answer 6

-Particles slide past each other, separation is greater than in solids and attractive forces are weaker.
-Lower densities than solids but can flow and be poured

Question 7

Describe using the kinetic model of matter how the particles are in gases?

Answer 7

-Particles are free to move, in random directions
-Forces of attraction are weak and their is high separation between particles
-They generally have low densities and can be compressed easily

Question 8

What is internal energy?

Answer 8

-Internal energy is defined as the sum of all the kinetic and potential energies within a system

Question 9

What factors affect internal energy?

Answer 9

-Temperature: a higher temperature means that the particles have a higher kinetic energy
-States of matter: gases have the highest internal energy and solids have the lowest
-Intermolecular forces: higher intermolecular forces means more potential energy

Question 10

How can you increase the internal energy of a system?

Answer 10

-Do work to the system by heating it up

Question 11

Why does steam at 100 degrees have more internal energy than water at 100 degrees?

Answer 11

-Steam particles have more kinetic energy than water particles
-Energy has to be supplied to the particles of steam to overcome the forces of attraction.

Question 12

What is Brownian motion?

Answer 12

-The random movement of small visible particles in a fluid due to collisions with much smaller, randomly moving atoms

Question 13

What are the different patterns of movement in solids, liquids and gases when heated?

Answer 13

-For solids the particles will vibrate more and still be held in their equilibrium positions.
-For liquids some heat will be transferred into translational kinetic energy and the molecules move past each other faster
-For gases, All heat is transferred into translational kinetic energy and particles will collide faster

Question 14

What is specific heat capacity?

Answer 14

-The amount of energy needed to raise the temperature of 1kg of the substance by 1K

Question 15

Define specific latent heat of fusion and specific latent heat of vaporisation?

Answer 15

-fusion: the amount of energy required to change the phase of 1kg of substance from solid to a liquid
-Vaporisation: the amount of energy required to change the phase of 1kg of substance from liquid to gas

Question 16

Why does internal energy change during a phase change but temperature does not?

Answer 16

-The temperature remains constant as there is no change in kinetic energy
-However the internal energy does change as there is a change in potential energy as the forces between the molecules are changing

Question 17

What is a mole?

Answer 17

-One mole of any substance is the amount of substance that will contain an Avogadro’s constant number of particles
-This amount is its relative atomic mass in grams for example 12g of carbon 12 contain one mole of substance

Question 18

What are the assumptions of the kinetic model of a gas?

Answer 18

1.Gas contains a large number of particles
2. Particles moves rapidly and randomly
3. All collisions are perfectly elastic
4. Negligible forces of attraction between particles
5.Time for collisions to happen is negligible compared to the time between collisions
6. Particles have negligible volume compared to the container

Question 19

What is an ideal gas?

Answer 19

-A gas that has an internal energy only in the form of random kinetic energy

Question 20

What is Boyles law?

Answer 20

-The volume of a fixed mass of gas is inversely proportional to the pressure exerted on the gas, under constant temperature
-pV= constant

Question 21

What is the pressure-temperature law?

Answer 21

-States that for a fixed mass and volume the pressure is proportional to the absolute temperature (the temperature scale involving kelvin)
-P/T(in kelvin)= constant

Question 22

What is Charles’ law?

Answer 22

-At constant pressure, the volume and temperature of a gas are directly proportional
-V/T=constant

Question 23

What is the ideal gas equation?

Answer 23

pV=nRT

p=pressure
V=volume of gas
n=moles of gas
R=molar gas constant
T=temperature (kelvin)