# Preface!✨

It’s your favorite material science & nanotechnology enthusiast! A couple of days ago, I explained sigma & pi bonds from organic chemistry, and how they can relate to chemicals used in the production of aerogels! You will not need to know this to understand today’s topic, but I highly recommend you check it out so you can “blow up” your chemistry teacher's mind! 😉

But for today’s topic, I want to discuss what it means to have a low density, the density equation, and why aerogel is the least dense solid. And I will attempt to explain all of it in under 5 minutes! So here we go, reader! 😤

# Aerogel Density Explained! 💡

## But What Is Density? 🤔

Density means the mass per unit volume of a material/substance. (m / v)

Mass means how much an actual object weighs.

Volume means the amount of space that a 3-dimensional object (like aerogel) takes up.

To find out the density of any object, we have to find the mass of the object, the volume of the object, and divide the mass by the volume to give us the density of the object.

However, don’t get confused with thinking that mass is the same thing. Mass does not equal density. You can have an object that has a lot of mass (weighs a lot) but has a low density (weighs so little in terms of the unit of volume).

The units for measuring density are grams per cubic centimeter (g/cm³.) The reason why we use g/cm³ is that there is no way for measuring density directly, so we have to use the units of measurement for mass & volume. For mass, we use grams (g), and for volume, we use cubic centimeters (cm³).

## So How Is Aerogel The Least Dense Solid? 🤔

The reason why aerogel is the world’s least dense solid is because of the network of pores and interconnected particles that make up the aerogel. But these particles that make up the aerogel are not close to each other, they are weakly bonded to one another.

This creates the vast emptiness inside the aerogel, but it also causes brittleness of the macroscopic aerogel.

However, this emptiness is what allows aerogel to be the least dense solid. The particles in aerogel are very far apart, which is the same as normal gas particles. Gas particles are spread out, which will increase the volume, and decreasing the overall density.

## How Much Is Aerogel’s Density? 🤔

The density of a centimeter of silica aerogel has a density of 0.1 g/cm³.

The density of air is around 0.001225 g/cm³.

That means that aerogel is almost 15 times heavier than air! That is very impressive for such a material! An easier way to know if the density is pretty low is to use the floating test. If an object floats, it is less dense than water (1.0 g/cm³). If an object sinks, it is denser than water.

# Closing Thoughts! 💭

Now you know what it means to have density and why you should not use the terms “light” or “heavy” when explaining density, because they don’t explain the concept of density!

See you tomorrow for Part 2 of Sigma & Pi Bonds! 👋🏽

# Vocabulary! 📓

Density → Mass per unit volume of a material/substance. (m / v)

Mass → How much an actual object weighs.

Volume → The amount of space that a 3-dimensional object (like aerogel) takes up.

g → Grams.

v → Volume.