THERMOCHEMISTRY (PART 1) - INTERNAL ENERGY

Question 1

1. What is Internal Energy?

Answer 1

• the sum total of all the energy of a system

Question 2

2. What is an example of an element that consists of Internal Energy?

Answer 2

• a Diatomic Molecule

Question 3

3. What are the 4 different factors related to a Diatomic Molecule?

Answer 3

1. Electronic Energy
2. Translational Motion
3. Rotational Motion
4. Vibrational Motion

Question 4

4. What is the Electronic Energy of the Nuclei?

Answer 4

• this is the energy possessed by the Electron Cloud
• this cloud is found around the positive nuclei

Question 5

5. What is Translational Motion?

Answer 5

• this is the energy at the centre of the mass of the
  molecule
• this molecule moves in 3 Dimensional space

Question 6

6. What is Rational Motion?

Answer 6

• this is the energy of the molecule
• as the molecule rotates around its centre of mass

Question 7

7. What is Vibrational Motion?

Answer 7

• the spring connecting two atoms
• the spring can contract or expand
• this increases and decreases its potential energy

Question 8

8. How do we measure the Internal Energy of a system?

Answer 8

• we measure the change in the Total Internal Energy
• ▵E = the change
  = the difference between the final
  and the initial energy

Question 9

9. What happens when the ▵E is less than Zero?

Answer 9

• the energy is given out to the surroundings
• E initial is higher than E final
• the energy in the system drops
• this is very similar to an exothermic reaction

Question 10

10. What happens when the ▵E is greater than Zero?

Answer 10

• the energy is taken from the surroundings
• the E final is higher than the E initial
• energy must be put into the system to reach its final
  state

Question 11

11. What does the Graph look like for a +▵E reaction?

Answer 11

Question 12

12. What does the Graph look like for a -▵E reaction?

Answer 12

Question 13

13. What kind of a reaction would holding an ice cube in the palm of your hand be?

Answer 13

SYSTEM:
- ice cube
- the system is going to gain heat

SURROUNDINGS:
- hand
- the surroundings will lose heat

NB:
- endothermic reaction
- +▵E

Question 14

14. What happens if you have a reaction in which the system is the hand and the surroundings are the ice cube?

Answer 14

• the system will lose heat
• the surroundings will gain heat
• the reaction will be Exothermic
• negative ▵E

Question 15

15. What are State Functions?

Answer 15

• these are the functions whose value depend only on
  the present state of the system
• this is not the path taken to get from one point to
  another
• they are independent from the path taken to get from
  one point to another

Question 16

16. What is an example of a State Function?

Answer 16

• the distance between 2 cities
• the distance between the 2 cities does not change
  regardless of the path taken

Question 17

17. What is a Path Function?

Answer 17

• these are dependent on the actual path that is taken

THIS TAKES INTO ACCOUNT:
- the total distance
- the total energy required
- total time taken
- total money spent
- total work done

Question 18

18. What are two Characteristics of State Functions?

Answer 18

1. They are reversible
2. The overall change in the system is zero
   
   • this is when you return to the initial state

Question 19

19. What is one characteristic of Path Functions?

Answer 19

• they are not reversible

Question 20

20. How is the Internal Energy of a State Function calculated?

Answer 20

• the displacement is zero
• the ▵E total = 0