MATTER AND ENERGY The two basic ideas in physics are matter and energy. In the past, physicists believed that matter and energy were "two separate ideas". Today, physicists have shown that "matter can be changed into energy and energy into matter".

We can explain this transformation by saying: "when a body releases energy it loses part of it's mass, when a body absorbs energy, it gains mass".

Other terms associated with matter and energy are inertia and friction.

Please click on the word below that you would like additional information on.

 Matter Energy Inertia Friction

What do you think that matter is?

Matter is "anything that takes up space and has mass". People, animals, houses, snow, leaves, oil, water are examples of matter.

When we say that matter takes space, we mean "two things can not be in the same place at the same time". If you are standing in one particular spot, nobody else can stand there, you have to move so another person can stand there.

Mass "is the amount of matter in an object". Small and light objects have less mass and they are easier to move. Big and heavy objects have more mass and they are more difficult to move. It takes less effort to move an empty box than a box full of books.

To find out about matter we use our senses. We feel matter with our skin. We smell matter with our nose. We hear matter with our ears. We taste matter with our mouth and we see matter with our eyes. A piece of ice feels cold and the fur of a cat feels soft to our touch. When our moms bake cookies we can smell them all over the house. If your sister drops a book, you can hear the noise when the book hits the floor. A piece of candy can taste very sweet or maybe very sour when we put it in our mouths. We use our eyes to determine if something is big or small, heavy or light, short or tall.

There are three states of matter: solid, liquid and gas. Solid matter has its own "shape and volume", like an apple or a boat. Liquid matter "takes the shape of its container", therefore you can change its shape without changing its amount. For example, you have a measuring cup filled with 8 oz of water and you decide to pour this water in a thin long vase, the 8 oz of water remain the same, but now its shape has changed to long and thin. Gas matter "has no shape". It just spreads out in its container. An empty glass is full of air.

Matter can change states, that means it can go from being solid to liquid, from liquid to gas, etc. If you leave a piece of ice on top of the counter, it will soon start to melt into water. If you leave a pot of boiling water on the stove, eventually the water will evaporate.

Matter "is made up of elements". It can be "a combination of different elements or it can be only one". The smallest possible part of an element is called an atom. Atoms of elements can be combined to make molecules. One molecule of water is made of 2 atoms of hydrogen and 1 atom of oxygen (H2O).

Matter can be mixed. When you mix two or more kinds of matter together you get a mixture. Sometimes the matter does not change "it just gets all mixed up". Like if you mix chocolate powder with milk. You get a delicious glass of chocolate milk.

Matter can change. If you have a piece of square paper and you decide to cut it in an oval shape, a physical change has just happened. If you decide to burn the paper, the paper became ash. This change is a chemical change.

Energy is "the ability to do work".

Energy is everywhere. Planes can fly because they are powered by gasoline, "a type of stored energy". We can watch television and play CDs because of the energy that the electricity produces. We can run, play and study because our bodies convert the food that we eat into energy.

In our planet Earth, the Sun is the major source of energy. We need the heat of the sun to grow plants, which provide the food that we eat. The Sun also evaporates the water that falls as rain to water the plants.

There are two kinds of energy: Potential Energy and Kinetic Energy. A baseball lying on the ground has potential energy, once somebody throws it the baseball's energy changes into kinetic.

Energy is always changing back and forth from potential to kinetic. This change is called "Transformation of Energy". Energy "can only be changed into another state of energy. It can not be created or destroyed".

Energy is measured in different ways. The most common are BTU (British Thermal Unit) and Joules (1000 Joules = 1 BTU).

When we feel cold, we like to rub our hands together, the faster that we rub them, the warmer that they get. This action is called friction. In physics, "friction is a force that opposes the motion of an object when the object is in contact with another object or surface".

There is no such thing as a totally smooth surface. Even if they look smooth to the naked eyes, if we look at them through the microscope we will see that they have ridges and grooves. Friction occurs when the "ridges or grooves of two different surfaces contact each other as they slide past each other".

There are different kinds of friction:

 Static Friction: "the force that keeps an object that is not moving in its place". A vase on top of a table is an example of static friction.

 Sliding Friction: "the force that occurs when two objects slide against each other". An example of sliding friction is striking a match against a rough surface.

 Rolling Friction: "slows down the motion of an object rolling on a surface". Rolling friction slows down the motion of a tire rolling along the pavement.

 Fluid Friction: "the force that slows down an object when it travels through a fluid". A fish swimming in the water is an example of fluid friction.

If you are riding in a van full of objects, and your dad pushes the brakes really hard, the van will stop and all the objects in the van will move forward, and so will you and your dad.

This action is called Inertia. "Inertia is a property of matter".

Isaac Newton, a 17th century scientist, described this property in his first law of motion. He said that "an object at rest has the tendency to stay at rest and an object in motion has the tendency to stay in motion with the same speed and direction, until an outside force acts on it". In few words, "an object keeps doing what it is doing until you or something else stops it or changes the direction".

Inertia is also "directly related to the mass of an object". A bigger object has more inertia than a smaller object. For example, if your dad's van was full of boxes, the smaller ones will be the ones that moved the most when he pushed the brakes.