In this area I will try to tie the concepts from class together into a coherent whole.
How does energy fit into chemistry?
Matter is "material" made, as you already know, of atoms. In chemistry we study static and changing material. To change material we are always including "energy" in the discussion. In order to understand matter, it is important also to understand how energy affects matter. Matter is changed by interacting with energy. Ultimately, matter may even be a form of energy. Einstein's famous equation: e=mc^2 implies that energy stored in "stuff" (any matter) is a huge amount! and that mass and energy can be intercoverted: we can change mass into energy ( we knew that already because we burn wood to create heat...) and energy into mass (this we have not been able to do yet.)
The largest, and most wasteful, release of energy is in nuclear bombs which release huge amounts of energy by converting a small unstable mass of material into pure energy. More on that in class!
What is energy?
One problem with the study of energy is that it is not directly measurable and is essentially an abstract idea more than a "thing." This makes it very difficult to illustrate or define and therefore very hard for students to grasp. We'll look at two types of energy that each is found in several forms. We'll use this U.S. Department of Energy as a reference. ["Energy" is so hard to describe that "How Stuff Works" does not give you any pages if you search for it!]
The (unhelpful) definition of energy is "the ability to make something happen." What this means, is that "energy can be harnessed to do something useful." For example, falling water can be harnessed to turn a wheel or a turbine. For this reason, we would say that "falling water is releasing energy." Kind of confusing, eh? Maybe a simpler definition is "energy is something that changes something else." For example, a piece of toast gets brown and crisp in a toaster, so the toaster is "using energy to toast the bread." Or when you make a spark, that spark gives off light, so the spark must be using/releasing energy. If you move your arm you must be "using" energy because you are changing the position or location of your arm.
Nonetheless, it is important to know that energy can be recognized or measured in basically two "forms." Energy is either energy of motion (moving) and this is called "kinetic" energy, or energy is stored (available but not being used) and this is called "potential" energy. In other words, in one form the energy is doing something (like causing movement) and in the other form the energy is latent, or stored and can be used but is not being used at the time.
For a good discussion with examples of these kinds of energy go to the U.S. Department of Energy site by clicking on this link.
Where does energy come from?
"Where does energy come from?" is a great question that raises some interesting questions about origin and cause of the universe. In my own opinion, studying this question with a judicious ultimately to God.
That, of course, raises the question about wether energy can be made or used up. That, however, will have to be attended to later. For now, take it as a premise that energy is eternal but it can change forms. When energy does change forms it because less useful. For example, gasoline stores a lot of energy, but when you burn it to make your car move what is leftover is heat and some other chemicals made from the gasoline.
Energy is important not only because it is useful for us, but because it directly relates to why certain materials are solids. liquids or gasses.
States of matter
All stuff (basically) exists in one of three phases: solid, liquid or gas. The reason for "why" one material is in its phase has to do with (1) the attraction between the atoms of the material (like the attraction between water molecules in a glass of water) and (2) the energy in the system. You can make a material move into another phase by adjusting the amount of heat or energy in the system.
What do I need to know about heat & energy?
Heat is a familiar and easily manipulated type of energy. Heat cannot be seen (except in its radiant form as infrared waves with special visualizing tools), but its presence can be detected through touch. So we will start with heat.
Heat is energy that is transferred between two objects or substances of different temperatures; heat typically flows from a warmer material to a cooler material. Generally, when heat is transferred to a material, the motion of its particles speeds up and its temperature increases, although heat and temperature are not the same thing, they are closely related.
There are three methods of heat transfer: conduction, convection and radiation.
Conduction transfers heat through direct contact. If two objects are placed in contact with each other, heat flows from the warmer object (with faster-moving particles) to the cooler object (with slower-moving particles) by the direct interaction of the particles. When the faster particles collide with the slower particles, they transfer some of their energy to the slower particles. This action of one particle hitting another and transferring energy is called "conduction." This chain reaction of moving - hitting - moving - hitting is what transfers the energy from molecule to molecule.
For example, when a hot pan is placed on a counter, the counter increases in temperature as the faster-moving molecules of the pan collide with and increase the motion of the molecules of the counter. At the same time, the molecules of the pan slow down, and the temperature of the pan drops. Some materials, such as metals, are good conductors of heat while other materials, such as glass, wood, plastic, and air, are not. Materials that are not good at transferring heat by conduction are known as insulators.
Convection transfers heat through the movement of fluids (which includes liquids and gases). When molecules of a fluid gain energy their movement increases. This movement causes the molecules to hit each other harder and they spread out from each other; as a group, their density decreases (same molecules take up more space). This decreases in density causes the group of molecules to be buoyant and they "float" to the surface of the fluid. In turn, colder molecules move into the space and are heated. This is why it is so efficient to heat a fluid from the bottom. (See lab Too Hot to Handle for a demonstration of this.) Some of the fastest cooking ovens are "convection" ovens that use fans to move the hot air to the bottom of the space and thus use the heat more efficiently to cook the food.
A pot of water heated on a stove provides an example. The pot itself, and then water at the bottom, becomes heated by conduction. When water is heated, it expands, becomes less dense, and rises up through the surrounding cooler water. The cooler, denser water then sinks to the bottom of the pot where it, in turn, is heated. The convection current—the circulating path of hot water rising and cold water sinking—transfers heat by actually moving the warmer water to a new area. It also forces the hot water to mix with the cooler water and increases conduction by bringing the cool water to the bottom of the pot.
Radiation transfers energy by electromagnetic waves [see video explaining radiation], a method in which heat can transfer even in the absence of matter (through outer space, for example). When electromagnetic radiation strikes an object, the energy carried by the electromagnetic wave is transferred to the object, causing the particle motion within the object to increase. For example, a microwave oven emits microwave radiation to transfer heat to food. Similarly, the reason that you can feel the warmth of an object at a distance, such as from the Sun or a light bulb, is due to the transfer of heat by radiation. Heat that you can feel with your skin is usually infrared radiation. While all matter emits and absorbs electromagnetic radiation, some materials are better at absorbing radiation than others; shiny surfaces, for example, tend to reflect rather than absorb radiation.
Although some radiation is visible, like visible light (red, orange, green blue, etc.) most is not. Infrared is not visible, although you can detect it by touch.
Interactive instruction on types of heat transfer; click here.
Why is heat important?
Is there such a thing as "no heat?"
Yes; there is something which has "no" heat; that point is absolute zero. A good introduction to what heat is, and an explanation of the idea of absolute zero, can be found at this site in Colorado.
It turns out that some time ago, scientists developed ideas that connected the pressure of a gas to the temperature. When a gas is hotter it takes up more volume and when it is cooler it takes up less volume. Ultimately this was extrapolated to mean: If the volume of a gas continues decreasing until it can decrease no further then that point will be the zero volume point; absolute zero.
Now a gas is a number of molecules flying around and banging into each other and into the side of the container. This hitting force is how a gas exerts a pressure. When a gas is heated the molecules move faster and hit each other harder so the pressure increases. When you cool a gas it exerts less pressure and, in principle, you can cool it so low that it will not be a gas; that molecules will stop moving and fall to the ground in a small, inanimate heap. This point is absolute zero.
Neat examples of heat principles
Heat waves: Heat waves are not really heat waves. Light travels through a clear medium but bends each time it reaches a medium of a different density. (You can show this in a fish tank witha flashlight). When air is heated it is less dense and so light bends differently than in cool air. Air is heated more closer to the surface of the earth (or the pavement or the ground) so the density of air is very low at the ground, when the ground is very hot. The light that travels through the air at the surface is bending each time it hits a pocket of cooler or denser and and to us this looks like the shimmering of the object whose reflected light we are seeing travelling through this air with variable density.
Shaving gel: One company invented a shaving gel called "Edge." The value of this unique product is that it gets your face "wetter" and therefore softer so the shave is less painful. it does this because the gel is more like a liquid than a foam, so you spread it on your face. But the gel turns into a gas at body temperature (the temperature of your face!) so as you spread it on your face it foams up and looks like normal "shaving foam."