1. What is science?
2. How is it done these days?
3. The origins of modern science.
4. Laws of motion, gravity.
5. The nature of energy.
6. Conservation of energy.
7. Heat.
8. The second law of thermodynamics.

• How does a fuel cell work?
• 2nd law of thermodynamics: stated 3 ways
1. Heat will not flow spontaneously from a cool to a warm body
2. You cannot construct an engine that does nothing but convert heat to useful work.
3. Every isolated system becomes more disordered with time.
• #1 relates to thermal motion of atoms
• #2 says that we cannot make a perpetual engine. Heat is always lost.
• Define efficiency
• Define order, disorder and entropy
• #3 the key to this statement is “isolated system”
• Heat death of the universe
• Does evolution violate the 2nd law?
• Why do we age?

• Hydrogen + Oxygen forms water, The Hindenburg explosion
• Fuel cells
• Forms of Energy:  Kinetic, Potential
• 1st law of thermodynamics: In a closed system energy is conserved.
• Anywhere in the universe we find that the behavior of energy is regular and predictable. The total amount of energy is a constant, though it is constantly changing form. But the changes in form are constrained to go in certain directions.
• These constraints are defined by the 2nd law of thermodynamics which can be stated in several different ways:
1. Heat will not flow spontaneously from a cold to a warm body.
2. You cannot construct an engine that does nothing but convert heat to useful work.
3. Every isolated system becomes more disordered with time.
• Let’s discuss each of these statements.

• Ice cream will warm up and melt if you have it outside on a warm day.
• Warm coffee will cool down.
• These are manifestations of the thermal motions of atoms.
• Fast-moving atoms tend to share their energy with slow moving atoms.
• This law does not say that we cannot make a cool object cooler. Look at refrigerators for example. A freezer is able to take energy from a cold region and make it even colder. The 2nd law does not say that this is a problem; it says that it cannot happen spontaneously. This means that you must expend energy to make it happen.

• Remember that energy is defined as the ability to do work. This version of the 2nd law implies that whenever energy is converted from heat to another form (e.g. heat to electric current) not all of the heat is available. Some must be lost and dumped into the environment. This does not mean that the energy is lost or destroyed, but that it cannot be used to make the electricity.
• Define efficiency: Efficiency is the ratio of the amount of work obtained from an engine with the amount of energy put into the engine. From the 1st law of thermodynamics, there is no reason that we could not transform 100% of the heat to electrical energy. However, the 2nd law tells us that it will not happen.
• Lets examine the details of how an automobile engine works in order to illustrate these things.

• Some heat is lost because of friction, but even if the engine was perfectly frictionless, it could not work with 100% efficiency. The reason is that you must return the engine to its original state. After the power stroke, you must get the piston back to the top. The hot air inside the piston must be expelled into the atmosphere.
• Define high-temperature reservoir: the system from which the energy is obtained.
• Define low-temperature reservoir: the system to which the heat energy is dumped.
• The 2nd law of thermo states that any engine operating between two temperatures must dump energy into the low-temperature reservoir. Once the heat has been dumped into the low-temperature reservoir, then it is no longer useable to run the engine.
• This is why gas and petroleum can only be used once. Moreover, they are inefficiently used to run engines.
• This form of the 2nd law applies to cyclic engines and not to other uses of energy. For instance, burning natural gas to heat your home does not drive an engine, and therefore there is no restriction on efficiency. That is why burning fossil fuels to heat your home is a more efficient use than using it to make electricity and then heating your home with the electricity.

• Define the temperature (must be in Kelvin) of the high-temperature reservoir to be T_hot and the temperature of the cold-temperature reservoir to be T_cold. Then the maximum theoretical efficiency that an engine can produce is

• Any loss of energy due to friction etc. will make the actual efficiency lower than the theoretical value.
• E.g. Coal-burning electrical generating station. T_hot = 500 K, therefore

• This means that most of the energy from such a plant is wasted. It does not matter how good the engineers are. In reality, they are very good, with the plants producing within a percent or two of this value.
• These sorts of efficiency studies can guide us as to how we use these resources. For instance, should we use oil to generate electricity and lose ½ of it as waste, or should we use the oil to make plastic?

• This version of the 2^nd law tells us that the universe is getting more disordered with time. Let us examine what this means.
• By the term “ordered”, we mean that the system (of objects, say atoms) is laid out in a regular and predictable fashion. E.g. a crystal structure
• In a disordered system, they are laid out in a non-predictable, chaotic fashion. E.g. gas.

• This may seem to be at odds with the idea that you can put water into the freezer and turn it to ice. This is taking a disordered state and ordering it. But the key to understanding this concept is the word “isolated” The refrigerator is not an isolated system, it is attached via a power cord to the power grid. The entire system is becoming more disordered, even though parts of it become ordered. Disorder does not have to increase in all parts of the system.
• The quantity that measures disorder or the degree of disorder is called entropy. The greater the entropy the greater the disorder.
• In a social sense, this law could be saying that society would tend to go into chaos without a concerted effort by its citizens.

• The discovery of the 2^nd law of thermo led to a feeling of gloom and doom.
• “This is the way the world ends, not with a bang but a whimper”. TS Elliot
• The belief was that the universe is winding down to a chaotic state where everything will be at the same temperature.
• Recent news, "...the findings support theories that the cosmos will continue its slow expansion toward nothingness ..."

• The progress of time is directional. Science cannot say why we perceive time to go only in one direction, but science can describe the effects of this directionality.

• Creationists who argue that life was created at one single moment often use the 2^nd law as an argument against evolution.
• They do not understand the 2^nd law.
• Their argument is that since life is a very highly ordered state that it could not form spontaneously.
• However, they are forgetting the part about the closed system. The system is the sun plus the earth. The sun is constantly burning out, become more disordered and spreading that energy around. As with the example of the ice cube, subsystems may become ordered.
• Perhaps we cannot state exactly how evolution proceeded, but we can say that it could do so without violating the 2^nd  law.

• The personal part of the 2^nd law is that we grow old and die. Humans dream and write about the fantasy of reversing the aging process. We see plenty of science articles about studies along these lines.
• However, what scientists have recently been learning is that we should be able to offset the aging process in some way. Of course, it will require an increase in entropy in other parts of the earth, i.e. it will require energy to do so.
• In general, we can observe that most life forms exist long enough to reproduce then they grow old and die.
• One school of thought suggests that our bodies were designed by nature to fall apart after the age of reproduction was over.
• Another school of thought suggests that we grow old simply because of general wear and tear. I.e. accumulated damage to our DNA.
• This school seems to be winning, pay attention to newspaper articles in this field!
  E.g. "Aging is a disease."
  "Antioxidants slow the aging process."