The best examples of calculating the density of a liquid: 3 core examples and more

Let’s start with three classic lab setups. These are the backbone examples of calculating the density of a liquid: 3 examples that show up in high school labs, college practicals, and entry-level research work.

Remember the basic density formula:

Density (ρ) = mass / volume

For liquids, we usually work in grams (g) and milliliters (mL) or cubic centimeters (cm³), so density ends up in g/mL or g/cm³.

Example 1: Measuring the density of tap water with a balance and graduated cylinder

You’re given a beaker of tap water and asked to find its density. This is the simplest example of calculating the density of a liquid, and it sets the tone for everything else.

Step 1: Measure the mass of the empty cylinder
Suppose you place a dry 50 mL graduated cylinder on a digital balance and record:

• Mass of empty cylinder: 42.50 g

Step 2: Add water and record total mass
You pour water up to the 40.0 mL mark and measure again:

• Mass of cylinder + water: 82.50 g

Step 3: Find the mass of just the water

• Mass of water = 82.50 g − 42.50 g = 40.00 g

Step 4: Use the density formula

• Volume of water = 40.0 mL
• Density = mass / volume = 40.00 g / 40.0 mL = 1.00 g/mL

That matches the accepted density of pure water at about 4 °C, and is close to typical room-temperature data reported in reference tables (for example, the NIST Chemistry WebBook, hosted by the National Institute of Standards and Technology: https://webbook.nist.gov/chemistry/).

This is one of the cleanest examples of calculating the density of a liquid: 3 examples often start with water for exactly this reason — it’s easy to compare your result to published values.

Example 2: Density of saltwater – why your result is higher than for pure water

Now you prepare a salt solution:
You dissolve 5.00 g of table salt (NaCl) into water and bring the final volume to 50.0 mL in a volumetric flask.

Step 1: Measure mass
Let’s say the mass of the salt solution (without the flask) is 54.00 g. (In a real lab, you’d subtract the mass of the empty flask the same way we did with the cylinder.)

Step 2: Apply the density formula

• Mass of solution = 54.00 g
• Volume of solution = 50.0 mL
• Density = 54.00 g / 50.0 mL = 1.08 g/mL

Compared to 1.00 g/mL for water, this higher density makes sense: you’ve packed dissolved ions into the same volume. Oceanographers track small changes like this to understand seawater salinity and circulation; NOAA (National Oceanic and Atmospheric Administration) has accessible background on seawater properties at https://oceanservice.noaa.gov.

This salt solution is one of the best examples of calculating the density of a liquid when you want to show how composition changes density in a predictable, measurable way.

Example 3: Density of an unknown liquid sample in a chemistry lab

Now imagine you’re handed a colorless liquid labeled “Sample X”. Your job: identify whether it’s more likely ethanol, water, or a heavier organic solvent, using density.

Step 1: Tare the balance with an empty container
You place a small glass vial on the balance and tare it to zero.

Step 2: Add a known volume of the liquid
Using a pipette, you add 10.00 mL of Sample X. The balance now reads:

• Mass of Sample X: 7.90 g

Step 3: Calculate density

• Density = 7.90 g / 10.00 mL = 0.790 g/mL

Now you compare this value with reference data. At room temperature, ethanol has a density around 0.789 g/mL, while water is about 1.0 g/mL. You’re clearly closer to ethanol. You can confirm with a database or handbook, like the NIST WebBook or a college chemistry data table from a site such as MIT OpenCourseWare (https://ocw.mit.edu).

This unknown-sample scenario is one of the most practical examples of calculating the density of a liquid: 3 examples like this are often used in teaching labs to connect measurement to identification.

2. More real examples of calculating the density of a liquid in everyday science

The three core cases above are the foundation. But in real life, examples of calculating the density of a liquid include everything from food science to environmental monitoring. Let’s walk through several more, each adding a layer of realism.

Example 4: Checking sugar content in soft drinks using density

Food and beverage labs regularly measure density to estimate sugar concentration.

Suppose you’re analyzing a cola.

• You measure 25.0 mL of cola.
• The mass of that sample is 26.3 g.

Density = 26.3 g / 25.0 mL = 1.052 g/mL.

Compared to water, that higher density reflects dissolved sugars and other solutes. With a calibration curve (density vs. sugar concentration), you can estimate grams of sugar per 100 mL. This is how quality control teams keep products consistent and verify nutrition labels.

This is a strong real-world example of calculating the density of a liquid because it connects a basic physics concept to the nutrition facts panel you see on every bottle.

Example 5: Measuring density of antifreeze in automotive maintenance

Mechanics and DIY car owners use density (often via a hydrometer) to check antifreeze concentration. The freezing point of the coolant in your radiator depends on how much ethylene glycol or propylene glycol is mixed with water.

Imagine you take a coolant sample and bring it into the lab:

• You measure 20.0 mL of coolant.
• The mass is 21.8 g.

Density = 21.8 g / 20.0 mL = 1.09 g/mL.

Reference tables from manufacturers or engineering handbooks relate this density to glycol percentage, which then tells you the approximate freezing point. In cold climates, that’s not just academic — it’s the difference between a working engine and a cracked block.

Again, this is one of the best examples of calculating the density of a liquid that has direct financial and safety implications.

Example 6: Density of blood plasma in medical research

In medical and biological labs, density matters for separating components of blood, designing IV fluids, and calibrating diagnostic equipment.

Let’s say a lab tech measures a blood plasma sample:

• Volume: 5.00 mL
• Mass: 5.25 g

Density = 5.25 g / 5.00 mL = 1.05 g/mL.

That’s consistent with published values for human plasma density, which generally falls slightly above water due to proteins and electrolytes. Organizations like the National Institutes of Health (NIH) and research hospitals such as Mayo Clinic (https://www.mayoclinic.org) publish data and studies that rely on accurate density measurements for fluids.

This is a more advanced example of calculating the density of a liquid, but it follows the exact same formula you used for tap water.

Example 7: Density changes with temperature – heating vegetable oil

Density isn’t fixed. It depends on temperature, and that matters in engineering, environmental science, and even cooking.

Consider a sample of vegetable oil.

At 20 °C:

• Volume: 50.0 mL
• Mass: 45.0 g
• Density = 45.0 g / 50.0 mL = 0.900 g/mL

You gently heat the same sample to 60 °C. The mass doesn’t change (still 45.0 g), but the volume expands slightly.

At 60 °C, you now measure the volume as 52.0 mL.

• Density = 45.0 g / 52.0 mL ≈ 0.865 g/mL

Same liquid, different temperature, lower density. Engineers account for this when designing pipelines and storage tanks, and physicists emphasize it in lab manuals for good reason.

This temperature effect is one of the more subtle examples of calculating the density of a liquid that often gets missed in basic classes, but it explains a lot of real-world behavior.

Example 8: Using a hydrometer to estimate density in a home brewery

So far, every example of calculating the density of a liquid has used a balance and a measured volume. But in brewing and winemaking, a hydrometer is the tool of choice.

A hydrometer is a weighted glass float that sinks deeper in low-density liquids and rises in high-density ones. It’s calibrated to read specific gravity, which is basically density relative to water.

Suppose your hydrometer reading for a batch of beer wort is:

• Specific gravity (SG): 1.050 at 60 °F.

That means the liquid’s density is 1.050 times that of water. If water is about 1.00 g/mL at that temperature, your wort density is roughly 1.05 g/mL.

Brewers use the difference between the starting density and final density to estimate alcohol content. Sites like university extension programs (for example, Washington State University Extension) and brewing science courses explain these relationships in more detail.

This hydrometer scenario stands out among real examples of calculating the density of a liquid because it shows how the same physics underpins an entire industry.

3. How to avoid common mistakes when working through density examples

By now, we’ve walked through far more than just 3 examples, but the structure behind them is the same. To get reliable results from any example of calculating the density of a liquid, keep an eye on a few repeat offenders.

Watch your units

Mixing mL and L, or g and kg, is a fast way to wreck otherwise good data. Before you plug numbers into the density formula, make sure:

• Volume is in a single unit system (all mL, or all L, not a mix).
• Mass is in consistent units (all g, or all kg, etc.).

If you’re comparing your result to a reference table from a site like NIST or a university chemistry department, always check what units they use.

Read volumes at eye level

Liquid in a cylinder forms a meniscus — a curved surface. For water and most aqueous solutions, you read the bottom of the meniscus at eye level. Misreading by even 1 mL can throw off your density in small-volume examples of calculating the density of a liquid.

Record temperature

Temperature changes density. If you want your result to be taken seriously (especially in 2024–2025 lab reports where data quality expectations keep rising), write down the temperature next to every density value. That’s standard practice in research labs and is reflected in modern lab manuals and safety documentation.

4. Why these examples matter in 2024–2025 labs and classrooms

Modern science labs are more digital and automated than ever, but the basic examples of calculating the density of a liquid still matter. Automated density meters, used in pharmaceutical and chemical industries, are calibrated and checked against simple water and ethanol standards — the same liquids we used in our early examples.

In environmental science, density measurements feed into models of ocean circulation, groundwater flow, and pollutant transport. Agencies like the U.S. Geological Survey (USGS) and NOAA still rely on careful fluid property data when they publish reports and open datasets.

In education, inquiry-based labs increasingly ask students not just to follow a recipe, but to design their own procedure for measuring density. That’s where understanding multiple real examples of calculating the density of a liquid becomes valuable: you can adapt the same logic to almost any situation.

Whether you’re measuring tap water in a high school lab or calibrating a hydrometer in a brewery, the workflow is nearly identical: measure mass, measure volume (or use a calibrated float), and do one simple division.

FAQ: Short answers based on real examples of calculating the density of a liquid

Q1. Can you give a quick example of calculating the density of a liquid?
Yes. If you have 25.0 mL of olive oil with a mass of 22.0 g, the density is 22.0 g ÷ 25.0 mL = 0.88 g/mL. That’s a classic example of calculating the density of a liquid using basic lab glassware.

Q2. Why do different examples of calculating the density of a liquid give different values for water?
Because temperature, dissolved gases, and impurities all affect density. Water at 4 °C is denser than water at 25 °C, and tap water with minerals will differ slightly from distilled water. Reference sources such as NIST list density values as a function of temperature for that reason.

Q3. Are hydrometer readings an example of calculating the density of a liquid?
Yes. A hydrometer doesn’t show you grams and milliliters directly, but it’s calibrated so that its scale corresponds to liquid density or specific gravity. When you read a value like 1.050, you’re effectively using a practical example of density measurement without doing the math yourself.

Q4. What are some everyday examples of liquids with densities lower and higher than water?
Lower than water: most vegetable oils, gasoline, and many alcohols (like ethanol). Higher than water: saltwater, syrup, honey, and many concentrated acids. Any of these can be used as an example of calculating the density of a liquid in a teaching lab.

Q5. How accurate do my measurements need to be for classroom examples?
For most school and introductory college labs, being within a few percent of the reference density is fine. What matters more is that you use consistent units, read instruments correctly, and can clearly explain how you got from mass and volume to density.