Scientific Facts, Hypotheses, Theories, and Laws

I like to teach the definitions and concepts of scientific facts, hypotheses, theories, and laws at the very beginning of the first science course during the high school years.  Younger kids can get these concepts as well, especially the middle grades crowd, but for sure by tenth grade your student should have a firm concept of what each of these terms means.

Below I will walk you through how I present these concepts to my kids.

defining hypothesis, theory, law

Taking Notes

First, they take notes while I write the information on a chalk board.  A wall chalkboard is a little luxury of mine and most people don’t have them in their homes.  You can also use a hand-held white board or sheets of printer paper taped up on the wall, temporarily with masking tape.

Note taking methods

  1. If I write it on the chalkboard, then the kids have to write it in their notes.
  2. I use numbered lists, bullets, indents, colored boxes around key ideas, arrows, pictures, and diagrams to make the notes more fun and organized.
  3. As I write things on the board, I also take the time to give examples, ask questions, allow them to ask questions and so on.

notes taken during a discussion about scientific facts, hypothesis, theories, and laws

Now we will move into the information for this particular topic: scientific facts, hypothesis, theories, and laws.  The things in bold below are the things I write up on the chalk board.  The other information is extra thoughts that I would share out loud, but not make them write. I have not shared everything I talked with my kids about because it would be too long in this post and because I share my beliefs about the world as I teach, which may or may not be your beliefs.  You should share your beliefs and your reasoning as you teach.


First I have my kids title their page of notes: “Scientific Method“.  We wrote another post about the Scientific Method which goes more into actually doing science and using lab write ups, this post is more about philosophy of science and definitions.


Facts – simple observations of natural things.

There are facts that can be found in morality or philosophy or religion as well, but these are not scientific facts.  Scientific facts only relate to the physical, natural world.

  • How do scientists come up with these facts?


Hypothesis – idea that can be tested

The idea in a hypothesis should be based on facts already observed.  I might observe that birds can fly and then come up with an idea about the structure of bird bodies that allows them to do this.  Then I would come up with a way to test my ideas.


Theory – well tested set of observations that explains why or how things happen in nature.

This is a tough to get concept sometimes because the way we use the word “theory” in everyday English is different from the way we use it when talking about science.  It does not mean a reasonable idea, or educated guess.  Instead it is a hypothesis that has been tested repeatedly through experimentation and/or observation and has been found to be consistent.  It also must explain “why” or “how”.

Germ theory explains that microbes are responsible for disease and can be transmitted to people (or animals).  It has been demonstrated through repeated experimentation and observation that this is true.  It explains how people get sick and how disease is spread.


Law – describes what happens.

A scientific law simply states what consistently happens.  If I toss an apple in the air it must come back down to earth. This is the law of gravity.  We have observed that this is always true. But the law of gravity does not explain why the apple comes back down.  If we knew why the apple falls we would call this the theory of gravity.  Since we have no idea how gravity actually works there isn’t currently a theory of gravity, but there is a law of gravity.

Limitations of Science

Science is fallible

I had my kids put this phase inside a box and then color in the box because it is important to understand that science isn’t perfect.  Long held beliefs about the natural world can be overturned in an instant by one experiment or observation.  A good example is Newton’s Laws of Motion.  Even though these are still taught to students they are in fact, not really true.  Further observations enabled scientists to understand that these “laws” only operate on a human scale, but not at all on massive scales of space or in the minuscule world of sub-atomic particles.

Though this may look like a weakness of science, in many ways it is a strength.  To constantly be striving, learning, growing, expanding, and thinking is a very human thing to do and that is what science does.  It admits when it is wrong and goes back to the drawing board.  It does not let one little mishap overthrow the whole thing.  We continue to pursue knowledge of the natural world even though we know some of what we “know” isn’t true.  If one scientific concept is found to be not true, we don’t give up all faith in science, we simply keep working at it.


  • Data might be flawed
  • Impossible to test all implications
  • Experiments might be flawed

Some of the reasons science isn’t perfect is because of mistakes people make or because of the sheer impossibility of accounting for everything in nature.

A good scientist is a skeptic.  She is always wondering why, and what if, and keeping the possibility  in her mind that conclusions already reached might not be entirely or at all true.  New information can overthrow entire systems of thought.  This actually occurs pretty often.

The scientific community might do thousands of experiments that seem to prove a scientific theory, but it only takes one experiment or observation to prove the theory is not right.

There is no such thing in science as an incontrovertible Truth.

More From Layers of Learning

Did you know we have a complete science curriculum for sale for kids from 1st grade to 12th grade?  Read about it in our Curriculum Guide.




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