Category Archives: Chemistry Lesson

Lesson 1: Introduction to Chemistry

For this lesson we’re going to learn what chemistry is, what the scientific method is, and why we should study chemistry.

Textbook Reading:  Chapter 1 The Chemical World (pp. 1-8)


In this section each week, I’ll add materials to supplement your readings, as well as propose some questions we will discuss in class.



Now that you are in a chemistry class, you might be wondering exactly what you will be learning. What is chemistry exactly?

You probably already have some ideas about what chemistry is from your past experiences. Do you visualize ball-like atoms, scientists in white coats, and/or beakers full of colorful liquids? How about loud explosions?

If you have studied biology, you may have learned it is “the study of living things,” a definition that seems pretty clear. In contrast, chemistry is quite difficult to define and there isn’t one, fixed definition used by everyone. In fact, some sources say chemistry is now changing so fast, and is part of so many other sciences, that it is impossible to define.

In the textbook, Tro gives the following definition on the bottom of page 3:

Chemistry is the science that seeks to understand what matter does by studying what atoms and molecules do.

Let’s examine some of the vocabulary he uses more closely.


The first thing we need to be clear about is what matter is. By definition, matter is anything that takes up space (or saying that in another way, has volume) and has mass. Many times you may hear matter defined as “stuff,  as in matter is all the stuff around us, and even the stuff that makes us up. Stuff sounds a little vague, so perhaps it would be clearer if we looked at what is not considered to be matter.



In this illustration the light socket, the light bulb, and even the chain are matter, but the electricity coming to the outlet and the light produced by the bulb are not. Things like sound, gravity and time are also not considered to be matter.

Atoms and Molecules

Matter is made up of particles called atoms. In the textbook, Tro introduces atoms as very tiny particles. Molecules are two or more atoms bonded together. We will learn a lot more about atoms and molecules in future chapters.


If you have taken other science courses before, you are probably familiar with the scientific method. If not, here’s a quick review:


First a scientist makes some sort of an observation, perhaps while out on a walk on the beach or in the lab while doing other experiments. That observation may generate a question in the scientist’s mind, which he or she might eventually use to formulate into a hypothesis (tentative explanation). If the hypothesis is testable, as it should be, the scientist will design and carry out an experiment, or even series of experiments, to test it. If the results of the experiment(s) work out, it confirms the hypothesis and the scientist may publish his or her work to communicate it to others.

If the experiment does not work out, the scientist may revise the hypothesis or throw it out altogether.

Throughout the experiments the scientist may make further observations, which lead to more hypotheses. The scientific method is not a linear, step-by-step process, but may be a complex and convoluted one.

Over time, as more and more scientists throughout the world test and confirm a given hypothesis or set of hypotheses, those may become a law. If the hypotheses and/or laws become well established and are deemed to have a sufficient power to explain phenomena, then they are “promoted” and considered to be theories.

Perhaps it would be easier to understand with a concrete example:

Fossil evidence suggests that dinosaurs became extinct rather abruptly approximately 65 million years ago. In 1978 Luis Alvarez, his son Walter Alvarez, and their coworkers made the observation that a thin layer of sedimentary rock formed 65 million years ago that contained unusually high concentrations of iridium, a rather rare metal.



Figure 1. Luis and Walter Alvarez are standing in front of a rock formation in Italy that shows the thin white layer of iridium-rich clay deposited at the time the dinosaurs became extinct. The concentration of iridium is 30 times higher in this layer than in the rocks immediately above and below it. There are no significant differences between the clay layer and the surrounding rocks in the concentrations of any of the 28 other elements examined. (b) Microphotographs of an unshocked quartz grain (left) and a quartz grain from the iridium-rich layer exhibiting microscopic cracks resulting from shock.

example of scientific method


(Click on the illustration to enlarge it.)

Further observations and experiments led them to suggest the iridium came from an asteroid hit that the Earth near the Yucatan Peninsula in Mexico, resulting in the extinction of the dinosaurs.

(These illustrations were from General Chemistry: Principles, Patterns and Applications, adapted by The Saylor Foundation under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License without attribution as requested by the work’s original creator or licensee.)

 Why we should study chemistry



Many chemists and others consider chemistry to be the “central science.” To understand what is going on in virtually all the other sciences, one must understand the atoms and molecules that make up matter. It is basic to what is going on in the universe.

Chemistry is a science that is central not only to other sciences, but also to many other fields. We need it to understand how the spark ignites hydrocarbons in an internal combustion engine, what to add to the mixture of pigments we use to paint the wall, or what are ways to make a better shampoo.

Think chemistry isn’t relevant to you? Check out these cool chemistry life hacks:


Discussion challenge:

Why do you want to study chemistry? Why might learning chemistry important to your life and career?

Think about it and we’ll discuss it more in class.

Congratulations, you made it through the first lesson!