Density of Water

Density of water is the ratio of the mass and volume of the water at room temperature is 998.2 kg/m³. The density of any substance is defined as the amount of mass present in the unit volume of the given substance. 

For pure water, the density is 1 gm/cm³ or 1000 kg/m³. Pure water’s density varies with temperature and reaches its highest point at a temperature of 4 °C, or 1000 kg/m³. 

The density of water is maximum at 4 °C.

What is the Density of Water?

The term “density” refers to how much volume (space) an object or substance occupies in relation to the amount of material it contains (its mass). Another way to think of density is the amount of mass per unit of volume. An object with a high density is solid and compact. The SI unit of Density is kg/m³ and g/cm³ in the CGS system. It is an intrinsic property of matter. 

Density of Water is 1 gm/cm³ which is not a coincidence. Density is the ratio of the mass of the matter and the volume occupied by it used to calculate the density of 1 g of water that occupies 1 cm³ volume. Furthermore, air pressure and atmospheric temperature also affect how dense water actually is. 

However, these differences in density are comparatively small, so you can continue to use 1 g/cm³ for water density unless you need to do highly specific calculations or the experiment is conducted in a condition with extreme temperatures or pressures.

However, the density of water for different metric systems is given below:

The substance whose density is less than water floats on the water and the substance whose density is greater than water sinks in the water.

The image below shows three containers in the first container the density of the cork is less than water so it floats on the water, in the second container the density of the wood is almost equal to the water so it partially gets submerged in the water, and in the third container, the density of cork is aluminium is greater than water so it sinks in the water.

 

Keep in mind that these water density figures only apply to pure water. The density of salt water (like the oceans) varies depending on how much salt is dissolved in the water. The density of seawater is normally between 1.02 g/cm³ and 1.03 g/cm³, which is somewhat greater than the density of pure water.

Properties of Water

Water is a strange liquid, it is the most important liquid for the survival of humans. Various properties of water are discussed below,

Density of Water Formula

The density of water is calculated using the normal density formula,

D = M/V

where,
D is the density of the water
M is the mass of the water
V is the volume of the water

We know that,

At room temperature, if the volume of water is 1 ml then its mass is observed as 0.995 grams. Now the density of the water is,

D = mass/volume

   = 0.995/1
   = 0.995 g/ml = 0.995 g/cm³

Learn more about Density and Structure and Properties of Water

How to Calculate the Density of Water?

A graduated cylinder is used to calculate the density of water. An empty cylinder is taken and weighed on a machine. This gives us the mass of an empty graduated cylinder, that is, m.

Now the required amount of water is filled in the cylinder and it is weighed again. This gives us the mass of the filled graduated cylinder, that is, m’.

Now the difference between the calculated masses would give us the mass of water. Thus,

Mass of water (M) = m’ – m

Volume of water (V) is found by using the marking on the cylinder. It is found that the volume of water is almost equal to its mass.

So, using the formula for density we get,

ρ = Mass of water/Volume of water

ρ = M/V                                                 [as mass (M) and volume (V) are almost equal]

ρ = 1 g/ml

It is concluded that the density of water is a constant value, that is, 1 g/ml or 1 g/cm³.

Density of Water at Room Temperature

At room temperature i.e. at the temperature of 20 °C to 25 °C the density of the water is 0.9982 g/cc, or 998.2 kg/m³. The mass of water is almost equal to its volume at room temperature and the water remains in liquid form at room temperature. Seawater has various salt and minerals dissolved in it, so its density is slightly higher than normal water. Normally the density of seawater is approximately 1027 kg/m³.

Factors Affecting Density of Water

A number of factors can affect a substance’s density. Some of the factors that affect water density are listed below:

The density of water is about 1 gram per cubic centimetre (1 g/cm³).

• Although the relationship is described as non-linear and unimodal rather than monotonic, it is temperature dependant.
• Liquid water tends to get denser when cooled from room temperature, yet it is believed that pure water reaches its maximum density at about 4 °C and from 4 °C to 0 °C the density of water increases, and this behaviour is called the anomalous behaviour of water.
• As it cools more, it has a tendency to expand and get less dense. Thus water is a strange liquid that gets denser to a specific point on cooling and then started to expand on further cooling.

Density of Water at Various Temperature Scales

The following chart shows the density of water (in gm/cm³) at different temperatures values (in °C)

As it is observed, water has a density exactly equal to 1 gm/cm³ only at 4 °C. Also, it has been observed that the density of water decreases with the increase in temperature. Ice has a lower density than water, which causes a drop in the density of water. This is the reason why ice floats on top of the water and why ice cubes don’t just fall to the bottom of a glass of water when you put them in it.

Anomalous Expansion of Water

Water behaves anomalously on heating i.e. its expansion is not linear. Its density first increased from 0 °C to 4 °C and then it started to decrease after that as its volume started to increase. 

Now it is evident that its density is maximum at 4 °C

The maximum density of the water is at 4°C which is 1g/cm³ or 1000 kg/m³. 

Density Vs Temperature

Since its density changes with temperature, water lacks an absolute density. The liquid form has a greater density than the solid form. To learn how density varies with temperature, look at the graph of density vs. temperature shown below.

 

Density of Water Maximum at 4 °C?

Water is a strange liquid and behaves anomalously. The density of water is maximum at 4 °C and this can be explained as,

• As the water freezes its particles come close till they reach their maximum density at 4°C at this temperature water is in a liquid state only.
• After this further decreases the temperature the water tends to freeze and acquire a solid state.
• One might think that solid water would be denser but as the water started to freeze it acquires a cage-like structure which eventually increases the volume of the water and this is the reason why ice float on the water.
• Now as we know if the volume increases the density decreases. Thus, the density of water decreases after 4°C. 

So it is clear that the density of water is maximum at 4°C

Check: Water Pressure Formula

Density of Water Experiment 

In order to understand more about the density of water, how it behaves, and comparison of it with respect to other substances. Let’s perform the activity mentioned below:

Take a small amount of some liquids that are viscous as water e.g. Liquid Soap, Milk, Sugar Syrup, Honey, Ethyl Alcohol, and Olive Oil in a test tube. Mix them well so that each of the substances cannot be observed clearly.

Now, leave it for a few hours so that the layer of each substance settles down at a certain level as shown below:

Now, it has been observed that different substance has different density This implies each substance weigh differently for the same volume. Because their weight varies, heavier substances tend to settle at the bottom, like honey, and sugar syrup and lighter material like olive oil and ethyl alcohol tends to float at the top.

Density of Common Liquids

Various liquids have various densities as they have different masses for a fixed volume of the liquid. The table discussed below tells us the density of various liquids at room temperature.

Read More,

• Pascal’s Law
• Buoyancy 
• Bernoulli’s Principle

Solved Examples on Density of Water

Example 1: Calculate the density of water if the mass of the empty graduated cylinder is 10.2 g and that of the filled one is 20 g.

Solution:

We have,

m’ = 20

m = 10.2

Calculate the mass of water.

M = m’ – m

M = 20 – 10.2

M = 9.8 g

So, volume (V) = 9.8 ml

Using the formula we get,

ρ = M/V

   = 9.8/9.8

   = 1 g/ml

Example 2: Calculate the mass of the filled graduated cylinder if the mass of water is 5 g and the mass of the empty cylinder is 15 g. 

Solution: 

We have,

M = 5

m = 15

Using the formula we have,

M = m’ – m

m’ = M + m

m’ = 5 + 15

m’ = 20 g

Thus, the required mass of filled graduated cylinder is 20 g.

Check: Difference Between Density and Specific Gravity

Density of Water – FAQs

The density of water is maximum at which temperature?

The density of water is maximum at 4°C  or at 39°F.

What is the density of water?

Density of a substance is defined as the mass of that substance distributed over a unit volume. It is denoted by the symbol rho (ρ). Its standard unit of measurement is kilograms per cubic meter (kg/m³) and the dimensional formula is given by [M¹L^-3T⁰].

Why density of water is more than ice?

The density of water is more than the density of ice because as the water forms ice its volume increases as it forms a cage-like structure 

Why does ice float in water?

At about 4° Celsius, water has its highest density. Ice floats because it has a lower density than liquid water. Upon freezing, the ice density decreases by about 9%.

How does temperature affect the density of water?

The density of water changes with temperature. It increases as water is cooled down to 4°C and decreases when the temperature goes either above or below this point. For example, at 100°C, the density is around 958.4 kg/m³, and at -30°C, it’s approximately 983.854 kg/m³​.

Why does the density of water have a maximum at 4°C?

At around 4°C, water reaches its maximum density due to a balance of competing molecular forces. Below this temperature, water begins to expand as it prepares to freeze, which is why ice floats on liquid water​​.

Does the presence of salts and minerals affect water density?

Yes, the density of water can increase with the presence of dissolved salts, minerals, and other substances. Seawater, for example, is denser than freshwater, with typical densities around 1027 kg/m³ at the surface due to the salt content​.

What is the density of seawater?

The density of seawater, at the surface 1027 kg/m³ approximately.

What is the density of water at room temperature?

Density of water at room temperature is 998.2 kg/m³. 

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