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When I'm teaching middle school science and I'm teaching the concept of matter I usually tell them that everything is made of matter except for 3 things.

Space-Time, Energy (light, heat, kinetic, potential, etc) and Abstractions (happiness, love, running, numbers, etc)

Although Space-Time is not on the syllabus the students love to hear anything that follow ''this is not on the syllabus but ...''

Is this a fair statement or am I leaving something out?

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    $\begingroup$ What does it mean exactly? One could argue that energy is an abstraction, or that happiness is made of matter (as a state of the brain). I don't think this question actually has a physics content, it's about general education, language or philosophy. $\endgroup$ – fqq Nov 16 '19 at 19:00
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    $\begingroup$ I recommend sticking with examples of what is made of matter: our bodies; the air; planets and stars, etc. And contrasting this with vacuum, such as outer space. $\endgroup$ – G. Smith Nov 16 '19 at 19:03
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    $\begingroup$ Making examples without defining what you mean by matter is meaningless. $\endgroup$ – GiorgioP Nov 16 '19 at 20:52
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    $\begingroup$ If you say that light is not matter, do you say anything about how do we know it? $\endgroup$ – GiorgioP Nov 16 '19 at 20:55
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    $\begingroup$ With this definition, you are left with abstractions only, since taking space is not applicable to space-time and a box with light inside does have energy ( $E=mc^2$). Energy in turn is a property of a physical system, it is not itself a physical system. In any case your students cannot check experimentally your claims about the mass, so you are asking them to trust you, instead of explaining them "how do we know that...". $\endgroup$ – GiorgioP Nov 17 '19 at 8:58
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It is fair for the middle school level. Mass-energy equivalence and the complications of space-time would make your lesson a bit more confusing so your statement should be good.

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Please note that light is not a form of energy, rather it carries energy, just as matter does. In my opinion, the most clear and unambiguous example of "stuff" that is not matter is in fact light. One might regard spacetime also as a "stuff", a physical entity, but that is a bit more muddled in how you define "physical" and which model you are using. Personally I'd regard the contents of the universe as matter and light, which have energy, and exist in spacetime. "Abstractions" are just one of many /emergent properties/ that result from this fundamental system.

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