Dr. Universe explains molecules

Ask Dr. Universe is a science-education column from Washington State University.

  • Thursday, January 31, 2019 2:05pm
  • Life
Illustrations by Rob McClurkan

Illustrations by Rob McClurkan

Dr. Universe: What are molecules? – Jolin, 9, Maryland

Dear Jolin,

A glass of water has more molecules than there are stars in the night sky. That’s what I found out from my friend Jack (Qiang) Zhang, an assistant professor of chemistry at Washington State University.

“Everything around us is made up of molecules,” he said. “And while these molecules may be different, they are all made of the same things.”

Those things are called atoms. Zhang told me we can think about atoms kind of like Lego blocks. Imagine that you have a pile of red Legos, yellow Legos, and blue Legos. Maybe you use them to build a tiny house, or you can use this same set of Legos to build something else like an airplane or a robot.

Just as you can arrange blocks in different ways, atoms arranged in different ways can make up different objects. There are a lot of atoms, but let’s talk about three of them. We can find their names on a big chart called the Periodic Table of Elements.

First, there is hydrogen, the smallest atom and the most abundant element in the universe. Then there’s carbon. Animals, like us, get carbon by eating plants or meat. And then there’s oxygen, which you might be familiar with because we all breathe oxygen molecules.

These atoms can do things individually, but when we combine them in different ways, they form all kinds of things.

You could make sugar, a sweet molecule that gives plants and animals energy. You could also use those same building blocks to make vinegar, a sour molecule and type of acid that we use in cooking.

One of the most abundant molecules on our planet is water. It can make trees grow tall, but through a process called erosion it can also break down the biggest mountains. It is made up of two hydrogen atoms and one oxygen atom, which is why some people will call it

H₂O.

Water and other molecules will undergo changes under different temperatures. When water gets cold it becomes a solid, called ice, but those very basic molecules still keep the same shape. Molecules are also always moving, said Zhang. Even in the wood that makes up your school desk, the wood molecules are vibrating ever so slightly.

Zhang said different molecules will sometimes interact with each other, too. For example, if you mix vinegar and baking soda together you are bound to see some bubbles start spouting. Here, the molecules that make up baking soda and vinegar start to re-arrange in a chemical reaction. In a way, it’s kind of like breaking apart your Lego creation to make something else. You can learn more about chemical reactions in this activity from the American Museum of Science and Energy. Tell me how it goes at Dr.Universe@wsu.edu.

Sincerely,

Dr. Universe

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