Thermodynamics

Image: http://en.wikipedia.org/wiki/Atom_(comics)

Energy Super Heroes

Projects due September 24

You must work at home on these. There’s not enough class time.

This week:1. Super power2. Name & origin story3. List of concepts your hero can demonstrate.

Rubric: Super Hero ProjectWeek 1

Objective Value

Hero is original 25

Super power relevant to our topic 25

Hero has a name and identity 25

List of concepts your hero can demonstrate (ie, what physics will you be showing?)

25

Thermodynamics

Thermo = heat

Dynamics = motion

Thermodynamics = the study of heat in motion

First Law of Thermodynamics

• “The total increase in the thermal energy of a system is the sum of the work done on it and the heat added to it.”

The Atom can reduce his size and mass so as to ride air currents (wind or thermal gradients).

How does the First Law of Thermodynamics explain this phenomena?

Kakalios, J., The Physics of Superheroes, pp. 132-136

Work?

• Jenna, Carl: The product of force and displacement in the direction of the force

• Nick: Picking up a book is work

• Alex: Pushing a box across the floor is work

Second Law of Thermo

• “Natural processes tend to go in a direction that increases the total entropy of the universe.”

http://www.grc.nasa.gov/WWW/K-12/airplane/thermo2.html

Entropy is a property of a system, like Temperature.

Third Law of Thermo

• “As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.”

Changing State

• Vocabulary– Melting point– Heat of fusion– Boiling point– Heat of

vaporization

(definitions on pages 252-3 in your physics book)

Image: http://www.humboldt.edu/~rap1/C107.F05/C107Exams_SG/C107Final_SG.htm

Changing State

Image: http://www.humboldt.edu/~rap1/C107.F05/C107Exams_SG/C107Final_SG.htm

Heat Needed to Melt Stuff

Q = mHf

Image: http://acephalous.typepad.com/acephalous/comics/

Heats of Fusion & Vaporization

Material Heat of fusion

Hf (J/kg)

Heat of vaporization

Hv (J/kg)

Copper 2.05 x 105 5.07 x 106

Gold 6.30 x 104 1.64 x 106

Mercury 1.15 x 104 2.72 x 105

Methanol 1.09 x 105 8.78 x 105

Water 3.34 x 105 2.26 x 106

Scientific Notation

• Which is bigger?– 8.25 x 104

– 1.13 x 105

Food for Thought

• Alcohol evaporates quickly. Why?

• Iceman (from the XMen) eats a normal diet of about 2500 calories per day, which is about 1.0 x 107 J of energy. How much water at 100°C could that much energy vaporize?

Image: http://acephalous.typepad.com/acephalous/comics/