Chemists joke about the dangers of dihydrogen monoxide. Depending on its form – solid, liquid, or gas – direct contact with it can burn you, or freeze the tissues and fluids in your skin. If you ingest significant quantities it can kill you. Of course, not ingesting enough will kill you too. According to these consequences, dihydrogen monoxide sounds like a nasty chemical. But it is just the humble water molecule. (I never said chemists make good jokes.) All of the dangers are true, though. Dihydrogen monoxide – H₂O – water – is a chemical which can burn you, cause frostbite, or dilute the salts in your blood so much that you die from water intoxication (hyponatremia). And just like water, chemicals are everywhere. Everything that you can see, smell, touch, and taste is made of chemicals. And everything you can’t.

It is impossible to see a single atom, even with the most powerful microscope. Although, scientists have managed to photograph an atom’s shadow. How few atoms does it take to cast a shadow? Just one. But while one atom alone cannot be seen, when many are joined together we see them everywhere. Or, we see the things they make up. Water. Trees. Cars. Houses. Hearts.

The Periodic Table of the Elements lists the species of atoms that have been discovered. There are one hundred and eighteen in total but only ninety-four occur naturally. The rest are synthetic and must be made in laboratories. Everything around us is a combination of these ninety-four elements.

At room temperature, some elements exist as liquids, some as solids and some as gases. They can be volatile like the metal sodium: soft, silvery white, and highly reactive. If you’ve ever seen a tiny piece of sodium dropped into water, you would remember it. The violent reaction breaks the bonds between the hydrogen atoms and the oxygen atom in the water molecule. Enough heat will be given off that the newly formed hydrogen gas explodes.

Some elements may be toxic like the gas chlorine. Like sodium, it’s too reactive to occur on its own in nature. When it is isolated, it is a yellow-greenish gas that is heavier than air. It smells a lot like bleach because it is just one of the elements that creates bleach. If you breathe in chlorine gas, you will feel like you’re choking and it can cause damage to your respiratory tract and lungs which is why it has been used as a chemical weapon.

But when sodium and chlorine join together into one substance, they become something necessary for life. Something we need every day to keep our hearts beating. They become sodium chloride – or salt.

Chemistry happens around us all the time. It is the change from rubbery dough to fluffy bread when heat is applied. It is how shampoo gets sudsy when you scrub it into your hair. It is why metals rust, or they don’t. Chemistry isn’t a secret or some sort of dark magic. It’s the explanation for everything that occurs around you and inside you – your heart pumping, or hurting.

Chemists study the composition, structure, properties, and relationships formed between substances, and how these substances can change. Reactions that are measurable. Changes that can be quantified. Attraction or the way elements and atoms bond. Why some bonds are hard to break apart and why others disintegrate, dissolve or separate easily. Chemistry is the understanding of matter.

Or maybe, it’s the understanding of things that matter. Relationships. Emotions. Attraction. Hearts racing. Body temperature rising. Stomach churning. It’s the properties of love and how it can change.

But love can’t be measured with a litmus test.