Thermal Physics

Question 1

Energy transfer between two objects happens when:

Answer 1

• One object does the work on the other object (it extact force from the other and make its move)
• By heating due to the temperature difference between two objects (conduction, convection, or radiation)

Question 2

What is the internal energy of an object?

Answer 2

• The sum of the ramdom distribution of the kinetic and potential energies of its molecules.
• Is the energy of its molecules due to their individual movements and positions.

Question 3

Internal energy of an object due to its temperature can be called:

Answer 3

Thermal energy.

Question 4

Internal energy of an object increases because:

Answer 4

• Energy transfer by heating
  or
• Work done on the object (ex. electricity)

Question 5

Internal energy of an object is constant when:

Answer 5

• There is no energy transfer (by heating or work done)
  or
• Energy transfer balance with each other (heating or work done)

Question 6

First Law of Thermodynamics

Answer 6

• The change of internal energy = the total energy transfer due to work done and heating.
• Energy can only be converted, never created or destroy
• The work done by an object is transferred by heating.
• The directions of the energies transfer are very important (determine increase or decrease of the object’s internal energy)

Question 7

What is a molecule?

Answer 7

• Is the smallest part of a pure substance. - Is made by atoms (ex. water= +2 hydrogen +1 oxygen)

Question 8

What is an atom?

Answer 8

• The smallest part of an element characteristic of that element
• (ex. hydrogen = a proton and an electron).

Question 9

What happens to the molecule when the temperature increases?

Answer 9

1- Molecules vibrate vibrate more.
2- Increases its kinetic energy.
3- After a limit, it will change its state (solid-liquid-gas).

Question 10

Characteristics of arregement in the three states:

Answer 10

• States: Solid -> Liquid -> Gas
• The particles are always the same, only the arregemet of the particles, the forces between them, the empty space between them, and the speed are different.
• Matter is made up of particles
• Particles and make up matter are constantly in motion
• Particles have empty spaces between them that contain nothing
• ## Particles attrac each other

Question 11

Charasteristics of solids:

Answer 11

• Particles are closely arrenged
• Particles do not move around but vibrate on their fixed position
• Paricles have small spaces between them
• The forces of attraction between the particles are very strong and hold them together

Question 12

Charasteristics of liquids:

Answer 12

• Particles are losely arrenged but close together
• Particles move around quiet fast and slide pass each other.
• Paricles have small spaces between them but larger than in a solid.
• The forces of attraction between the particles are weaker, so the particles are not held together and move around.

Question 13

Charasteristics of gas:

Answer 13

• Particles are not arrenged in any particular way.
• Particles move around much faster than liquid (they move ramndonly).
• Paricles the biggest spaces between them.
• The forces of attraction are extremely weak, so they move freely

Question 14

Thermal equilibrium

Answer 14

• Two objects at the same temperature.
• There is no transfer by heating

Question 15

Celsius scale

Answer 15

• Unit: °C
• 0° = Ice point
• 100 ° = Steam point

Question 16

Absulute scale (Kelvin scale)

Answer 16

• Unit: Kelvin “K”
• Absolute zero:
  - Lowest possible temperature
  - 273.15 K, also known as triple point, is where ice, water and vapour coexist.
• There is no knowledge of any substance reaching 0 K

Question 17

Formula for Celcius and Kelvins

Answer 17

Temperature in °C = absolute temperature in kelvins -273.15