Density of Water - Formula, Factors, Temperature, FAQs
Water is one of the most essential substances for life on Earth, and its physical properties play a crucial role in nature and daily activities. Among these properties, density of water is especially important in understanding concepts like floating, sinking, and temperature effects. Density is defined as the mass per unit volume of a substance, and for water, it is approximately 1 g/cm³ at 4°C, where it reaches its maximum value. This unique behavior makes water different from most liquids. In this article, you will learn about the definition, formula, factors affecting density, and why water’s density is important in physics and real-life applications.
This Story also Contains
- What is Density?
- What Is the Density of Water?
- Why is Water's Density Unique?
- Properties of Water
- Factors Affecting the Density of Water
- Density vs Temperature
- Density of Water at Different Temperatures
- Density of Water Experiment
- Density of Several Liquids
- Important Point
What is Density?
The density of any material can be measured by dividing the mass of that material by its volume. Basically, the density of any material measures the mass of any material in a particular volume.
The mathematical expression for density is shown below:
Density $=\frac{\text { Mass }}{\text { Volume }}$
SI unit for density = kilogram per cubic meter, i.e., kg/m³
CGS unit for density = gram per cubic centimeter, i.e., g/cm³
For example, if there are two materials that are of the same volume but different densities, the higher-density material will be heavier than the material that possesses lower density. The floating property of any material is based on the density of that material, whether it will sink or float.
What Is the Density of Water?
The density of water can be calculated by dividing the mass of water by the volume of water. The density of water is approximately 997 kg/m³. This means that 997 kilograms of water is present in 1 cubic meter (1 m³). The density of water is temperature-dependent.
Why is Water's Density Unique?
Water’s density is unique because it does not behave like most substances when it is cooled.
For most liquids, density increases continuously as temperature decreases.
Water behaves differently: its density increases only up to 4°C.
At 4°C, water has its maximum density.
Below 4°C, water expands and its density decreases as it turns into ice.
Properties of Water
| Property | Value |
| Chemical Formula | H₂O |
| Density | 997 kg/m³ |
| Molar Mass | 18.01528 g/mol |
| Boiling Point | 100°C |
| Melting Point | 0°C |
| Physical State | Liquid (at room temperature) |
| Colour | Colourless |
| Odour | Odourless |
| Taste | Tasteless |
| Specific Heat Capacity | High |
| Solubility | Universal solvent |
| Maximum Density | At 4°C |
| Surface Tension | High |
Factors Affecting the Density of Water
There are a few factors that affect the density of water. Some of these are mentioned below:
Temperature
This is mentioned above in the article as well, that temperature affects the density of water. This is because the density of water depends upon its crystal structure, and if the temperature varies, the space occupied by the molecules of water also varies.
Salinity
Salinity means the amount of salts dissolved in water. Seawater is denser than normal freshwater. This is because there is a huge amount of salt dissolved in the seawater, which increases the density of the seawater. So, it becomes heavier than nonsaline freshwater. This is the reason why some objects float in seawater but not in freshwater.
Pressure
The density of water is affected by pressure in very small amounts. This is because the water is incompressible. But still, water becomes a little denser when pressure is increased.
Density vs Temperature
There is no absolute density of water because the density of water is dependent on temperature. The density of water in the liquid phase is higher than the density of water in the solid phase. The temperature versus density graph is shown below to understand how the density varies with temperature:
Density of Water at Different Temperatures
The table below shows how the density of water changes with temperature on both Celsius (°C) and Fahrenheit (°F) scales. It also highlights that water has maximum density at 4°C, which is an important concept in physics.
| Temperature (°C) | Temperature (°F) | Density (g/cm³) | Density (kg/m³) |
| 0 | 32 | 0.99984 | 999.84 |
| 4 | 39.2 | 1 | 1000 |
| 10 | 50 | 0.9997 | 999.7 |
| 20 | 68 | 0.99823 | 998.23 |
| 30 | 86 | 0.99667 | 996.67 |
| 50 | 122 | 0.98806 | 988.06 |
| 70 | 158 | 0.97776 | 977.76 |
| 90 | 194 | 0.96531 | 965.31 |
| 100 | 212 | 0.95835 | 958.35 |
The information from the table mentioned above indicates that the density of water decreases with an increase in temperature. The density of water is highest at 4°C (39.2°F).
Density of Water Experiment
To better understand the density of water, here's an experiment shown below. For which we need a large glass tube or a glass container, honey, water, coconut oil, and a few food colorings.
Firstly, pour one-fourth cup of honey.
Then, gently pour one-fourth cup of colored water over the honey.
And in the last, cover the colored water with one-fourth cup of coconut oil.
It's important to note that different compounds have varied densities, which means that even for the same volume, they weigh differently. For example, heavier substances, like honey, tend to settle at the bottom, while lighter substances, like oil, prefer to float at the top.
Density of Several Liquids
The table below shows the density of various common liquids, which is useful for understanding concepts like floating, sinking, and specific gravity.
| Liquid | Density (g/cm³) | Density (kg/m³) |
| Water (at 4°C) | 1 | 1000 |
| Ethanol | 0.789 | 789 |
| Glycerin | 1.261 | 1261 |
| Mercury | 13.534 | 13534 |
| Seawater | 1.025 | 1025 |
| Acetone | 0.791 | 791 |
| Milk | 1.035 | 1035 |
| Honey | 1.42 | 1420 |
| Sulfuric Acid | 1.83 | 1830 |
| Olive Oil | 0.915 | 915 |
Important Point
- Density of water is maximum at 4°C
- Ice floats due to lower density
- Density depends on temperature, salinity, and pressure
- Water’s anomaly is crucial for life on Earth
Frequently Asked Questions (FAQs)
Around 4° Celsius, water reaches its maximum density. Ice has a lower density than liquid water, hence it floats. The density of ice falls by around 9% as it freezes.
Ocean water has a density of roughly 1027 kg/m3. at the surface.
Water has a density of 997.77 kg/m³ at room temperature (22° C).
Water never has an absolute density since its density varies with temperature.
Only water molecules are attracted to one other. The only thing that attracts oil molecules is other oil molecules. Because water is denser (heavier) than oil, they cannot combine. Oil floats on the surface of the water.
Specific gravity is the ratio of a substance’s density to the density of water. A specific gravity of less than 1 means the substance is lighter than water, while a value greater than 1 indicates it is heavier.
The presence of dissolved salts increases water's density. Seawater, for example, is denser than freshwater because of its higher salt content.
Dissolving salts in water and increasing the temperature leads to an increase in the density of water.
Yes, density affects the water level of water bodies. The water bodies with highly dense water/saline water will sink down.
If the density of any object is less than the density of water, then the object will float on the surface of the water.
