What Is Volume In Chemistry?

Kate Onissiphorou

by Kate Onissiphorou

16th March 2022

Volume is a measure of the amount of space that matter occupies. Matter is defined as a physical substance that occupies space and has a mass. 

In physical sciences like chemistry, the standard unit of volume is cubic metres (m3). From this, other units are derived including litre (L) and millilitre (mL). As chemistry experiments typically involve relatively small quantities of liquid solutions, it’s more common to express volume in millilitres rather than cubic metres.

Many aspects of chemistry require volume to be measured with a high degree of precision. It’s vital when determining the composition of sample substances, for instance, or when synthesising various chemical compounds.

Unlike mass, volume can change depending on factors such as the state of matter, temperature and pressure. For example, the volume of gas depends on the volume of its container. Even solid objects like cotton or styrofoam can be shrunk due to the spaces in their macroscopic proportions.

Such variability means a more precise definition of volume is necessary. This is usually predicated on specific parameters like temperature and pressure. Any change in these parameters will also alter the volume.

What is the Definition of Volume in Chemistry?

All types of matter occupy space, and this is what volume is. 

In science, volume is a measure of the amount of three-dimensional space an object fills. It’s usually measured in cubic metres based on the SI or metric system. 

Volume can be represented by three axes length, width, and height. In practice, however, volume in chemistry is commonly measured in litres and millilitres. This is because most laboratory experiments in chemistry use solutions, liquid mixtures, and suspensions.

Chemicals being measured in ml

Precise volume measurement is crucial to ensuring the right chemical reactions and rate of reactions occur. It’s important for both chemistry analysis and the synthesis of chemicals. 

But while measuring the volume of solids (even those with irregular shapes) and liquids is relatively easy, measuring gas is more problematic.

The volume of gas is directly dependent on its container, meaning no fixed volume can be stated without referencing the volume of the container. Nonetheless, the volume of a gas is still directly proportional to temperature and inversely proportional to pressure. See the summary of gas laws below: A table showing the gas law formula

How to Calculate Volume in Chemistry

There are several ways to calculate the volume of a substance. The most suitable method will depend on the state of matter and other factors such as temperature and pressure.

For solids and liquids, calculating volume is relatively straightforward. If you know the density and mass of the substance, then the volume is simply the ratio between the two.

A graphic illustrating the density formula

As you can see, density is defined as the unit of mass per volume of a substance. By simply rearranging the terms, we can derive the volume of a substance by dividing the mass by the density.

Density is fairly constant under standard conditions (0 °C and 1 atm). Pure water has the highest density of 1,000 kg/m3, which can be more precisely expressed as 0.9998395 g/ml. Based on this, you can easily calculate the volume of water at mass. Both pressure and temperature are held at standard conditions. Even if the conditions are not standard, the effects on the volume of solids and liquids are negligible.

However, it’s a very different situation when it comes to gases. In this case, you’ll need to consider the three gas laws as summarised above.

What is Molar Volume in Chemistry?

Molar volume in chemistry is based on Avogadro’s hypothesis. It simply states that gases of equal volume at standard conditions have the same amount of particles.

Graphics showing Avogadros' hypothesis

The total volume of a gas is mainly made up of empty space between the particles. One mole of any gas has a volume of 22.4L under standard conditions. This translates to the Avogadro’s number, which is equivalent to 6.02×1023 particles.

What is Net Volume in Chemistry?

Net volume in chemistry may refer to the delivered volume during titration, which can be derived from the volume measurements in the buret.

To calculate net volume, you simply subtract the initial volume from the final volume. Net volume may also refer to the remaining volume of a pure substance after the impurities have been removed. For example, the volume of tap water samples may be reduced once the air and solid impurities are taken out.

How to Find Volume Ratio in Chemistry

Volume ratio refers to the proportion of gases that react to form a product. Let’s take nitrogen and oxygen, for example. When these gases react they form nitrogen dioxide, as shown in the balanced equation below.

The Volume Volume Stoichiometry equation

We can easily calculate the volume equivalents of the moles based on Avogadro’s molar volume hypothesis.

In the example above, it takes one volume of nitrogen and two volumes of oxygen to produce two volumes of nitrogen dioxide. Under standard conditions, one molar volume of gas is equivalent to 22.4L.

What Unit is Used to Measure Volume in Chemistry?

There are various units of volume you can use to measure the three-dimensional space occupied by substances. The most important point is to use the units consistently to avoid confusion and miscalculations.

For example, if you’re using millilitres in your measurements, do not use ounces or gallons as well. Instead, you’ll need to convert these units to ensure any measurements are uniform and consistent.

In practice, the most common unit used in chemistry to measure volume is the millilitre, because of the small volume of samples used in experiments. Millilitres and litres are also easy to convert as they’re based on the metric system. Plus, there’s no need to write superscripts such as in cubic metres (m3).

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