Matter And Elements

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Context

The universe is made up of essentially an infinite number of substances. How do we keep track of all of them?

What is matter?

The grade school definition of matter is a good one: anything that has mass and takes up space.

Explanation

When we talk about matter we are thinking about things that are physical, things that you can touch or feel and that can be manipulated. Some materials can be very small, but if we have enough of it we can hold it and move it around. Heat is not considered matter. You can feel it, but you can't hold it and carry it from one place to another. The same could be said of things like love and joy. They don't have any mass associated with them.

Mass can be thought of as the amount of substance. It is generally given in units of grams (g) or kilograms (kg). Two grams of water has less substance than ten grams of water. The more substance you have, the more grams it would be. The amount of space something takes up is its volume. Volume is given in units of liters (L) or milliliters (mL). Under normal conditions one gram of water takes up one milliliter of space. A mL of water takes up about the same amount of space as the end of your index finger to the bottom of the fingernail. Measure out that much water and you could see how much a gram of water is.

There are too many substances to be able to keep track of them all. Biologists have come up with ways to classify plants and animals, but that is still pretty complicated and it only covers a small fraction of all substances. It would be nice if we could find a small number of substances that are used to make everything else.

This section will help you:

  • Understand what matter is.
  • Understand what elements are.
  • Understand how new substances are formed.

Model

All matter is made up of elements. Any particular substance is either one of the elements or a combination of two or more of the elements. We can describe any matter that we have observed using the elements. As they say in grade school; the elements are the building blocks of all matter.

How many elements are there? It turns out that there are less than a hundred naturally occuring elements plus a few man-made ones. The latest one I have heard of is number 114. That is certainly better than the close to infinite number of substances that we can identify. It is even better than that. In the end most of the substances we observe are made from around 25 elements. In other words, if we carefully study the 25 most prevelent elements we will be able to describe most of the world around us.

Chemistry is about taking substances (that are made of elements or combinations of elements) and combining them with other substances to create new substances that have different properties from any of those that you start with. It is a matter of rearranging the elements into different combinations to make new materials. Why the elements rearrange themselves is the topic of a future section.

Any change that produces a new substance is called a chemical change. Changes that don't produce new substances are physical changes. When paper is completely burned it produces carbon dioxide (CO2) and water (H2O). When wood, coal, gas, or any of our common fuels are burned they also produce carbon dioxide and water. These are chemical processes where new substaces (different from what you started with) are formed. If you rip a piece of paper into small pieces you still have paper, just small pieces of paper. That would be a physical change.

Thinking Questions

  1. Chemical changes create new substances. Can the new substances contain elements that are not found in the original substances?
  2. Some periodic tables list 103 elements, others list 109. Can you explain this?
  3. What can you say if ashes are formed when you burn a piece of paper?
  4. What is the difference between an atom and an element?
  5. Is there anything in our universe that isn't made of matter?