Energy and Heat

Energy is, in a way, the "money" of nature - nothing can happen without it, it comes in many forms that can be changed into each other without changing the amount (like a dollar bill changed for 4 quarters or 10 dimes or any other combination). Living things must get it from somewhere, and spend it to do the things they need to do. It's NOT made of atoms (so it's not a material) but atoms and molecules can have energy in them. It can also be present without any atoms nearby - e.g. light in outer space.

Some types of energy are:

motion - any material object, small or large, from pieces of atoms to galaxies, has energy if it's moving, more energy if it's faster (E =mv²/2)
atoms and molecules are constantly moving and jiggling; this energy is called "heat", and faster motion is more energy is hotter
light is a kind of energy that doesn't need atoms; when it hits atoms it can make them move (light energy converted into heat - does Sunlight feel warm?)
chemical energy is stored in fuels and batteries
electrical energy can be converted into light (lightbulb), heat (electric stove), motion (electric motor), etc.
many other kinds...

Heat Energy

Heat is a particularly important form of energy - it's everywhere, it has many important effects (in particular, on the estuarine environment), and its various effects are easy to understand. A good exercise in "Scientific Method" is to make predictions based on the "kinetic theory of heat" i.e. heat is the motion of atoms and molecules", then test those predictions experimentally.

Pondering some questions might suggest suitable predictions, and ways of testing them:

which takes up more room, cold or hot water? can you name a practical invention that exhibits the answer?
which will break apart and dissolve a salt crystal faster, cold or hot water? Why? try it experimentally!
what happens to a solid whose molecules move faster and faster? (it melts - crystal structure breaks apart)
what happens to a liquid whose molecules move faster and faster? (it boils - molecules separate and fly about independently, singly)
what happens to a gas whose molecules are slowed down? (condenses)
will a gas dissolve better in hot or cold water? (cold water slows down and captures gas molecules better - very important question for life in estuary waters!)