When you learn about air pressure, you’ll hear that it’s caused by the weight of the air pressing down on us and other things around us. But what does that really mean? Do gases like nitrogen, oxygen, and carbon dioxide have mass? If so, how much do they weigh? Read on to find out! When we think about something having a weight, we imagine it as having a measurable force. So when you read about air pressure is from the weight of air above us, it’s because those gases have density and volume but not a measurable force. That doesn’t mean gases don’t have mass. To understand why this is true, let’s first look at what we mean when we say something has mass. All matter has mass—even space itself! Mass is a measure of how much “stuff” there is in an object. It measures how much resistance an object has to acceleration when force is applied to it. So anything with mass will resist movement or acceleration under outside forces (such as air pressure).

**Do Gases Have Mass?**

**Yes, gases do have mass. The SI unit of mass is the kilogram (kg). One kilogram of gas has a mass equal to the mass of one liter of the gas at standard temperature and pressure (STP), which is equal to 1.293 82×10 kg/mole.**

**Why Do Gases Have Mass?**

**1. Gases have a volume, but not a density.**

The volume of a gas is proportional to the pressure and the temperature, which means that gases with the same temperature and pressure will have the same volume. The density of a gas is proportional to the mass of each molecule (which depends on its size), so as you raise the pressure or lower the temperature, you’ll increase or decrease the density of a gas.

**2. Gases resist movement and acceleration under outside forces.**

Gases are made up of atoms that are too small to be measured by our senses. However, because gases have mass, they resist outside forces such as air pressure and acceleration very well when those forces are applied to them. This is why we can hold our breath underwater without getting hurt but not in space without a spacesuit!

**3. Gases are made up of smaller particles and molecules.**

Gases are made up of a lot of different kinds of particles and molecules. Some of them are too small to be seen, but that doesn’t mean they don’t have mass. If you were able to weigh the tiny parts that make up a gas, you wouldn’t be able to do it with a scale—you would need a microscope or spectrometer to count them!

**How To Measure The Mass Of Gases?**

**Find the Volume of the Gas**

Before you can find the density of the gas, you need to know the volume in which it’s contained. To do this, you can use a gas syringe to measure the total volume of the gas. A gas syringe uses Boyle’s law to measure the volume of a gas that’s trapped in an enclosed space. Boyle’s Law states that the volume of a given amount of gas at a given temperature is directly proportional to the applied pressure. In the case of a gas syringe, the trapped gas is in a fixed space. The syringe contains a fixed amount of water, and the volume of the gas trapped in the syringe is directly proportional to the applied pressure of the gas. To use a gas syringe, you first need to put the gas in a container such as a vial or a flask. Then, you fill the syringe with water until the water level is at the same level as the gas in the container. This means the syringe will contain the same amount of water as the gas in the container.

**Find the Density of the Gas**

The density of a gas is an important factor in calculating its mass of a gas. In order to find the density of the gas, you’ll need to use a volumetric flask. A volumetric flask contains the gas you want to measure in a fixed volume. The amount of gas will be determined by the shape of the flask and the pressure the gas is under. Once the volume of the flask and the amount of gas in it is known, the volume of the gas can be found by using its pressure and temperature. The temperature and pressure of the gas are important as they affect its density. With the above-mentioned equations, we can find the density of the gas.

**Measure the Mass Based on Density and Volume**

Now that we have the volume and density of the gas, we can find the mass of the gas by using the equation below. $$ Mass = \frac{Volume}{Density}$$ The density of the gas can be found using the above-mentioned equations, and the volume of the gas can be found using the syringe. It is important to note that for this equation to be valid, both the volume and density must be expressed in the same units. Volume must be in ml, and density must be in kg/ml.

**Convert to Molar Mass**

The molar mass is the amount of substance in a given amount of a substance. In other words, it’s the mass of a substance per mole of that substance. In our case, we have the mass of the gas, and we want the mass of the substance. This can be achieved by converting the mass of gas to the molar mass. The equation is as follows: $$ Molar Mass = \frac{Mass}{Molar Volume}$$ The molar volume of a gas can be found using the ideal gas law. The molar volume is the volume of a given amount of a substance under standard conditions.

**Convert from Molar Mass to Daltons**

The molar mass of a substance is the mass of that substance per mole of that substance. The molecular mass is the mass of a substance per molecule of that substance. The molecular mass is usually measured in Dalton, which is equivalent to 1 gram. To convert from molar mass to Dalton, we need to use the molecular formula. The molecular formula is the formula of a molecule with the amount of each element shown as a percentage. For example, if you wanted to calculate the molecular mass of water (H2O), you’d need to know that each water molecule is made up of two hydrogen atoms and one oxygen atom. Thus, the molecular formula of water is H2O. To find the molecular mass, you multiply the atomic mass of each element (which can be found on the periodic table) by the number of atoms in the molecule.

**Find the molar volume of the gas**

The molar volume of a gas can be found using the ideal gas law, which states that the volume of a given amount of a substance under standard conditions is proportional to its pressure and temperature. The temperature and pressure of the gas are important as they affect its density. With the above-mentioned equations, we can find the density of the gas.

**Find out how much of that is just carbon dioxide**

The next step is to find out how much of the gas is carbon dioxide. You can do this by finding the percentage of carbon dioxide in the gas by using a gas analyzer. To do this, you’ll need to take a sample of the gas and put it into the analyzer. Once you know the percentage of CO₂ in the gas, you can find the mass of carbon dioxide in the sample by using the equivalence method. The equivalence method uses the molar masses of the reactants and product of a chemical reaction to determine the amount of each substance in a sample. For example, if you have a given sample of CO₂ and O₂, and you want to find out the amount of each in the sample, you can do so using the following reaction:

**CO****₂ + O****₂ ****⇋ CO + CO****₃**

This means that a sample of CO₂ and O₂ will react together to form CO and CO₃. You can use the molar masses of CO₂ and O₂ to find out the amounts of each present in the sample. With the above equation, you can find out the amount of CO₃ in the sample. Now you know that CO₃ is just CO₂ with an extra oxygen atom. So all you have to do is find the mass of CO₂ in the sample and subtract that from the total amount of CO₃.

**Measure the CO****₂ by itself**

Once you know the amount of CO₂ in the sample, you need to find its mass by using the same equation as in step 3.

**Calculate the final mass based on everything you know.**

In order to calculate the final mass of the sample, you have to add up the mass of the sample and the mass of CO₂.

**Summary**

Gases like nitrogen, oxygen, and carbon dioxide have mass because they have volume. But they have no measurable force because they’re in random motion and can’t be controlled. That’s why they have no measurable weight. That said, they do have measurable density. The density of a gas is related to its mass. A gas with a high density has more mass than a gas with a lower density. When you consider the total amount of gas molecules in a given space, you can calculate the overall density of the gas.