1. Introduction to Energy

2. About 13.8 billion years ago…
The universe existed as a singularity
Infinite density
Infinite temperature
The laws of normal space-time did not exist

3. BANG!!!!

4. Our universe is created
BANG!!!!
Our universe is created

5. Following the Big Bang…
The universe began to expand outwards

6. Following the Big Bang…
The universe began to expand outwards
All matter and energy that has ever existed and will ever exist in our universe was created by the big bang
Are matter and energy the only substances in the universe?

7. Dark Matter
Scientists have observed events in the universe that cannot be explained by ordinary matter and energy
This forced scientists to infer the existence of a hypothetical type of matter called ‘dark matter’
The name comes from the fact that dark matter is ‘invisible’ because it does not interact or emit observable electromagnetic radiation (visible light, infrared, etc.)

8. Dark energy
Scientists have also observed that the universe is expanding at an accelerating rate
This cannot be explained through matter, energy, or dark matter
Scientists have labelled the driving force behind the expansion ‘dark energy’

9. Universe composition
In fact, ordinary matter and energy comprises only 5% of the total mass-energy in the universe
95% of the energy-mass in the universe has been inferred and not observed!

10. Conservation of Energy
As stated previously, all matter and energy that has ever existed and will ever exist in our universe was created by the big bang
The Law of Conservation of Energy
Energy can neither be created nor destroyed, merely transformed

11. The Law of Conservation of Energy
Energy can neither be created nor destroyed, merely transformed

12. The Law of Conservation of Energy
Energy can neither be created nor destroyed, merely transformed
Energy ←→Matter For this unit, we will ignore these types of transformations.

13. The Law of Conservation of Energy
Energy can neither be created nor destroyed, merely transformed
Energy ←→Matter
Energy type←→Energy type
What do we mean by energy type?

14. Energy classifications
Energy can be classified in several ways:
Microscopic versus macroscopic
Kinetic versus potential
Microscopic energy: refers to the energy of the particles within matter (recall the Kinetic Molecular Theory)
Macroscopic energy: refers to the energy of an object

15. Energy classifications
Energy can be classified in several ways:
Microscopic versus macroscopic
Kinetic versus potential
Kinetic energy: the energy of motion
Potential energy: stored energy

16. Energy classifications
Energy can be classified in several ways:
Microscopic versus macroscopic
Kinetic versus potential
Within these energy classifications are many types of energy which we will be examining over the coming weeks

17. Energy classifications
Energy can be classified in several ways:
Microscopic versus macroscopic
Kinetic versus potential
Within these energy classifications are many types of energy which we will be examining over the coming weeks
Thermal
Gravitational
Chemical
Nuclear
Solar …

18. Energy classifications
Energy can be classified in several ways:
Microscopic versus macroscopic
Kinetic versus potential
Within these energy classifications are many types of energy which we will be examining over the coming weeks
But what is energy? Brainstorm

19. Energy definition
Energy is a challenging concept to understand and explain

20. Energy definition
Energy is a challenging concept to understand and explain
Energy is an abstract concept that describes the state of matter and its potential to change state due to interactions
What we care about is not what energy is, but rather, what energy does
Let’s examine energy using a money analogy

21. Money as an analogy for energy
How would you define money?

22. Money as an analogy for energy
How would you define money?
Money, in and of itself, is kind of meaningless. We think of money mostly in terms of what we can use it for. When money is sitting in your bank doing nothing, its worth is an abstract idea to describe how much you could buy with it

23. Money as an analogy for energy
How would you define money?
Money, in and of itself, is kind of meaningless. We think of money mostly in terms of what we can use it for. When money is sitting in your bank doing nothing, its worth is an abstract idea to describe how much you could buy with it
Energy is similar
On its own, energy is simply an abstract concept we created in order to describe states of matter, and how they can change
For example:
Temperature is a measurement of how much the particles in matter are moving
Kinetic energy is a way of understanding how matter is moving
Potential energy is a way of understanding how matter could move

24. Money as an analogy for energy
How would you define money?
Money, in and of itself, is kind of meaningless. We think of money mostly in terms of what we can use it for. When money is sitting in your bank doing nothing, its worth is an abstract idea to describe how much you could buy with it
Energy is similar
On its own, energy is simply an abstract concept we created in order to describe states of matter, and how they can change
For example:
Temperature is a measurement of how much the particles in matter are moving
Kinetic energy is a way of understanding how matter is moving
Potential energy is a way of understanding how matter could move
Let’s extend this analogy to better understand the conservation of energy

25. Let this piggy bank represent the total amount of money you have….

26. The money you have can be categorized in two ways:

27. The cash that you have to spend…

28. And the money saved in your bank account.

29. You can deposit cash into your bank account…

30. Or withdraw cash…

31. But the amount of money you have remains constant.

32. In order to change the amount of money you have, you either need to earn money…

33. Or spend money.

34. However, imagine that the money you earn is your allowance for doing chores around the house…

35. And the money that you spend is to pay back your sibling for money that you owed them…

36. Then, if we examined the amount of money in your household, it would remain constant regardless of your earning and spending

37. In order to change the amount of money in your household…

38. Your parents must either externally earn money…

39. Or spend money externally.

40. However, if we examined the Earth as a whole…

41. The amount of money in the world remains constant, regardless of your family’s spending/earning

42. Similarly….

43. Imagine that this box represents an object.

44. The amount of energy this object has comes in two types:

45. Kinetic energy (energy of motion)…

46. And potential energy (stored energy).

47. Energy can be converted from potential to kinetic….

48. And vice versa…

49. But the total amount of energy of the object remains constant.

50. In order to change the energy of an object you must either externally input energy… for example, by heating the object
For example heating the object

51. Or lose energy externally, perhaps by losing heat to the surroundings.

52. However…

53. If we consider the universe as a whole…

54. The total amount of energy will always remain constant.
If we consider the universe as a whole

55. The moral of the story…
Within a finite system (analogy→ your household):
Energy can be converted between potential and kinetic without changing the overall amount of energy
Energy can enter or leave the system due to external interference
Within the universe as a whole (analogy→ the planet):
The amount of energy will always remain constant