Internal energy and temperature

Question 1

When does energy transfer take place between two objects?

Answer 1

• one object does work on the other object
  
  • i.e. one object exerts a force on the other object and makes it move

Question 2

What is internal energy of an object

Answer 2

the sum of the random distribution of the kinetic and potential energies of its molecules

Question 3

What is the internal energy due to temperature?

Answer 3

sometimes called the thermal energy

Question 4

When does internal energy of an object increase?

Answer 4

• energy transfer by heating the object
• work is done on the object, e.g. electricity

Question 5

What is the first law of thermodynamics?

Answer 5

• in general, when work is done on an object and/or energy is transferred by heating:
• the change of internal energy of the object = the total energy trasnfer due to work done and heating
• direct of energy trasnfers are important to determine whether the internal energy is increasing or decreasing

Question 6

Describe the arrangement of a solid

Answer 6

• solid
  
  • molc held due to forces because of the electrical charges of the protons and electrons
  • molc vibrate randomly around fixed positions
  • higher the temp, more they vibrate
  • if temp raised enough, solid melts, molc vibrate so much they break free from eachother and the susbtance loses its shape
  • energy supplied to melt a solid raises the potential energy of the molc because they break free from eachother

Question 7

Describe the arrangement of a liquid

Answer 7

• molc move about at random in contact with eachother
• forces between molc are not strong enough to hold the molc in fixed positions
• higher the temp, faster molc move
• the energy supplied to a liquid to raise it temp, increases KE
• heating causes vaporisation
  
  • molc have sufficient KE to break free and move away from each other

Question 8

Describe the arrangement of a gas

Answer 8

• molc move about randomly but much further apart on average than in a liquid
• heating a gas or a vapour makes the molc speed up and so gain KE

Question 9

What effect does increasing the internal energy of a substance

Answer 9

increase the kinetic and/or potential energy associated witht the random motion and position of its molecules

Question 10

What is thermal equilibrium

Answer 10

Question 11

How is the celcius scale defined?

Answer 11

• ice point (OºC), temperature of pure melting ice
• steam point, 100ºC, temperature of steam at standard atmospheric prssure

Question 12

WHat is the absolute scale of temperature?

Answer 12

• units of kelvins
• defined in terms of
  
  • absolute zero, 0K, lowest possible temperature
  • the triple point of water, 273.16K, which is the temperature at which ice, water, and water vapour co-exist in thermodynamic equilibrium
  • ice point is 273.15, therefore ºC = temp in kelvin - 273.15

Question 13

What is absolute zero?

Answer 13

• lowest possible temp
• minmimum internal energy