1.2 Property Values

Atoms matter. In fact, atoms are matter. More to the point, atoms are matter made up of matter. For the purposes of this course, in general, we will be considering three of the building blocks that make up an atom: the proton, the neutron and the electron.

Matter is, for lack of a better term, stuff. That's it. There's no mystery. It's just stuff. So let's take a look at stuff, and more importantly, what stuff has in common.

All stuff has mass. It's there. It exists. It's impossible to put stuff in the same space that other stuff occupies. Quite a few people confuse mass with weight. Mass is not weight. This is important, repeat after me. Mass is not weight. Let’s look at an example. Suppose we have a 300 pound rock here on Earth. On Earth, that rock weighs 300 pounds. Any one of us would be hard pressed to move that rock from our back yard. We would probably just plant flowers around it and call it landscaping. However, if we were to fly that rock to the moon, that rock would weigh only 50 pounds. Most of us could manage 50 pounds. We would probably move the rock out of our moon back yard and not think twice, but wait a minute, that rock is still the same rock. It hasn’t changed. It still has the same number of atoms as it had on earth, but it weighs less. That's because weight is a function of gravity. The gravity on the moon is one sixth the gravity on earth so it weighs less, but its mass is constant. Mass is a constant property of matter, and in this course, mass is what we will be considering.

The other property that all matter has in common is electrostatic charge, positive, negative or neutral. When you go to pick up a bag of potato chips and don't get a shock, it's because the net electrostatic charge of all the matter that makes up that bag of chips is electrically neutral. However, when you scuff your feet on shag carpet and reach for a door handle, you may receive a static shock. This is because while walking across the carpet, your body picked up some extra electrons, lots of extra electrons in fact so when you touch the door handle, those extra electrons go rushing for the door and give you that shock.

Now that we understand the two most important properties of matter, we have to have a way of measuring them. After all, that's what scientists do, they measure. Let’s start with mass. It’s safe to say that we can all agree that atoms are very, very small. Well sub-atomic particles are even smaller. Thus they have an even smaller amount of mass. Therefore we need a common measuring stick with which to measure atomic mass. That measuring stick is the Atomic Mass Unit.

We use Atomic Mass Units in the same way we use any unit of measure. Just like there are 5 pounds of potatoes, there are 5 Atomic Mass Units. By adopting our own unit of measure, we keep the math simple. As we progress, we will have to compute different amounts of energy based on mass. Using numbers like 4.076 is far easier than using expressions like 1.66x10-24 . (the mass of an Atomic Mass Unit in grams) Believe me when I tell you, as we move farther along in the course. You’ll be thankful that we're minimizing our use of exponents.