1. Conservation of Energy

2. Conservation of Energy
P.E  K.E.  P.E.  K.E. … Is energy lost?
No! Energy is converted!

3. Law of Conservation of Energy
Energy can be neither created nor destroyed.
The total energy in a “closed” system is always the same.
The energy may be in different forms, but the amount will be equal.

4. Conservation of Energy
Thermal Energy produced by friction is not useful energy-Why?
It IS NOT used to do work.

6. Perpetual Motion
A machine that would run forever without the addition of energy.
Some energy is wasted due to the thermal energy produced, so perpetual motion is not possible.
So How does the “drinking bird” work? Read page 133 to answer this.

7. ANATOMY OF A HAPPY DRINKING BIRD - HOW IT WORKS - The techie stuff.
Technically, the Drinking Bird is a type of "Heat Engine". But thankfully you won't need a degree in physics or thermodynamics to understand the basics of how it works! The body of the bird comprises 2 glass "bulbs", one for the head and The glass tube which interconnects the two bulbs dips deep into a special liquid (usually coloured methylene chloride) in the body. one for the lower body. An important fact is that the bird will "drink" providing the head bulb is slightly cooler than the body bulb (i.e. there is a "temperature differential"). The head is usually coated in a red felt-like material which absorbs water when the bird "drinks". Evaporation of water from the head causes the head to become cooler than the body. By lucky coincidence, the swaying motion of the bird assists the evaporation. Although the head and upper part of the glass tube appear to be "empty", they are actually full of invisible vapour from the methylene chloride. Methylene chloride is good for this because it doesn't take much heat energy to turn it into a vapour (It has a "low latent heat of evaporation"). Because the head is cooler than the body, some of this vapour condenses inside the head, like steam when it touches a cold window. As this vapour "shrinks" into minute droplets of fluid, it takes up a lot less space. This makes the pressure inside the head slightly lower than the body, causing the liquid to be sucked up the tube. You could also think of it as the "hot" fluid in the body making "steam" above itself, which blows the liquid up the tube (vapour pressure); it's all relative. The main thing is, the body is always warmer than the head. It's not the same a thermometer, though, because it does not rely on expansion of the liquid itself, which is insignificant. It's the pressure of the vapour that does the work. As the liquid rises up the tube, it gradually changes the centre of gravity of the bird. This makes it tip over more and more until eventually it tilts into the water. If everything is adjusted just right, then as it tilts over, the end of the tube inside the body comes out of contact with the liquid. Instead of pushing the liquid up the tube, the vapour above the liquid in the body can now quickly rush up the tube, equalising the pressures in head and body. As this happens, the liquid which has moved up towards the head now gurgles back down into the body. This rapidly moves the centre of gravity back to the lower body, and the bird swings back away from the glass.
When you understand how the bird works, you will see how you can even "trick" it to "dip" with no water at all: If you shine a lamp towards only the bottom part of the bird, this slightly warms it (compared to the head), so there is the necessary "temperature differential" and it should "dip". If you have just shown your friends how the bird works (with water), then you may perhaps puzzle them again by removing the glass, and watching it continue to drink long even though the head has become dry, secretly using the warmth from a lamp nearby (which may have been on before). Take care, though, because excessive heat will burst the glass and make a terrible mess! (Thanks to Jan at "Arabesk" for this interesting trick