Doctors say it every day -” water is essential for your health.” Is water that important?
Well, it regulates your body temperature, helps your brain function, and did I mention it – it helps excrete your body waste through urination, perspiration, and defecation.
Now we know about water, but what is the density of water? If you’re still in school or like to study physics, “For any substance, the density is the mass per unit volume.” But if you don’t know or have doubts, no worries. Here in this blog, we will discuss “Density of Water” in detail, which will be helpful in your exam when you calculate a value using the density of water.
So, what is “Density”?
The density of any object or substance is defined as the mass present in a unit volume of that object or substance. If you study the gas theory, you will find another useful notion: number density. If m is mass and V is volume, then material density is given by ρ=m/V. And, if N is the total number of particles, then the number density will be n=N/V, where. Density is an intrinsic property of matter, and it is expressed as g/cm3 in CGS and kg/m3 in SI methods. In most places, the density of water is expressed as 1 g/cm3, but in some cases, you might find a different value with a different unit. For example, the density of water can be written as 1 g/ml (water’s density is gram per milliliter) or 1 g/cm3 (1 gram per cubic centimeter). Here is a simple chart for your understanding of “water density”:
|Density of water g/mL||1 g/mL|
|Density of water g/cm3||1 g/cm3|
|Density of water lb/ft3||62.4 lbs/ft3|
|Density of water kg/m3||1000 kg/m3|
Water’s density depends on the area’s temperature and air pressure. These variations in density are very less. Unless you need to know the exact data or the experiment in an extreme temperature/pressure area, you can use 1 g/cm3 for water density. When talking about density vs. temperature, we all know that water remains in a liquid state at room temperature. The density of seawater is higher than normal water because of the presence of salt and minerals. At the sea surface, the seawater density is about 1027 kg/m3.
Well, you must remember a fact about water density. We know water density can be expressed in different units, such as lb/ft3 or g/ml, or g/cm3, but the actual density of water is not 1 g/ml, a bit less than 1. The maximum density of water is 0.9998395 g/ml at 39.2° F (4.0° C), but the “Density of Pure Water” is different at different temperatures. Remembering a list of values is tough so you can refer to this table:
Did you know ice is less dense than water?
Unlike ordinary liquids, water density decreases from 4 degrees C to 0 degrees C. Above 4 degrees C, the density of water decreases with increasing temperature. This behavior is called the “density anomaly.” Due to this property, the density of ice is less than the density of water at 4 degrees C. Surprisingly, almost all of the volume of an iceberg lies below the waterline, not above it. Upon freezing, ice density decreases by about 9 percent. This property is significant for life. If water were less heavy than ice, the ice would sink to the bottom of oceans and lakes and freeze from the bottom up. But as you might know, water is an excellent thermal insulator; deep lakes might never thaw in the summer.
In cold regions (during winter and normal), the atmosphere’s temperature slowly decreases to 0 degrees C and further below. The water on the surfaces of oceans and lakes cools down, and it becomes heavy. Following the density rule, the cold water comes down, and the hot water rises. This convection process goes on until the water of lower surfaces reaches a temperature around 4 degrees C. At this point, the density of the water is maximum, the water from the upper surfaces of lakes and oceans cannot come down, and the convection process stops. Then the upper layers of lake water and ocean water cool down and become ice. That ice then floats on the surface of the lake or ocean water. However, the lower layers of the water stay at 4 degrees C, which is sufficiently warm for any aquatic animal to survive.
Now, coming to the effect of pressure on density. The normal density is – density increases when the pressure increases and decreases when the pressure decreases. As pressure increases, the molecules of any substance come closer, resulting in a higher density. On the other hand, when pressure decreases, the molecules go far from each other. Due to this reason, the density reduces. And the same logic applies to water also. Pressure affects density, but water isn’t very compressible, so it is not usually a significant factor.
How to Calculate the Density of a Liquid
Now you know the density of water at different temperatures, but what if you want to find the density of some other liquid and not water? Don’t worry; it’s quite easy! Just divide the mass by its volume, and you will easily find any substance’s density. Here is the formula for density: ρ=m/v; the symbol ρ represents the density, ‘s pronounced as “rho.”
You can try to find the density of milk, seawater, glycerin, and some other common liquids using this formula. There are 3 simple ways to calculate density, depending on whether you’re trying to find the density of an irregular object, a regularly shaped object, or just any liquid.
If it’s a regular object, such as rectangles, triangles, squares, etc., you have first to calculate the mass and volume of that object. The mass of an object means how much it weighs. Based on their height, length, and width, all regular polygons have an equation for determining their volume.
For example, say you have a piece of an aluminum piece (rectangular) that weighs 865 g. It’s dimensions are 10cm x 8cm x 4cm. And, you have to find its density. It’s easy. You can do it in just 2 steps. At first, multiply the width, length, and height (equation for the volume of a rectangle) and find the volume of the piece.
V = 10cm x 8cm x 4cm = 320 cm3
Now you know the volume, you need to divide the mass by the volume to get the density of the aluminum sheet ρ=m/v = 865g/320cm3 = 2.7g/cm3. So the density of aluminum is 2.7g/cm3.
But what if it’s an irregular piece of aluminum or any other object? How to find the volume in that case?
If the object is in an irregular shape, you can’t calculate its volume easily. You need to add some more steps before you find its density. First, find a cylinder, fill it with water, and place the irregular object in that cylinder filled with water. Now measure the volume of water it displaces. Do you know Archimedes’ Principle? It states that an object displaces a volume of liquid equal to its volume. Now you know the amount of water displaced by the aluminum piece, use the normal density equation ρ=m/v to find the density of any regular substance or object.
So if you had a different, irregular piece of aluminum that weighed 550g. Suppose the piece displaced 204mL of water in that graduated cylinder. So your density equation will look like
ρ = 550g/204mL = 2.7g/mL. But the aluminum sheet was a solid object, so if you want to find the density of a liquid, pour the liquid into the graduated cylinder, check its volume, and then follow the last step, which is nothing but to calculate the density that liquid.
The easiest way to measure the density of any liquid, including water, is to use a hydrometer. A simple hydrometer is nothing but a plastic or thin glass tube with a bulb-shaped at one end. The scales on a hydrometer can be calibrated to Brix, Alcohol, Baume, API, and others for specific chemicals. If you look closely at the hydrometer tube, you can see those marked lines on the stem, which indicate how far the bulb sinks in the liquid. The higher the bulb floats, the higher the density, and the lower the bulb sinks, the lower the density of that liquid. It would help if you took a liquid with known density, and then you can calibrate by floating the Hydrometer in that liquid.
Water is the standard liquid because it has a specific gravity of 1.000 at about 4°C.
Other than the 3 ways mentioned above, you can find the density of a liquid by measuring volume and mass.
- First, note down the weight of a graduated beaker or
- Then choose the liquid, pour and record the volume
- Now weigh the glassware filled with the
- Next, find the mass of that. Add up the mass of glass & liquid and subtract the weight of the glass from that value.
- Now find the density of the liquid by dividing the mass of the liquid by the
Hydrometers have many uses, but before you use them, you must have a general idea of the scale you need and the anticipated value on that specific scale for the process you are doing. Hydrometers are also used in the dairy industry to measure the fat content of milk, which is also called Lactometers. If you want to know the sugar content of any wine or beer, you can use this Hydrometer and decide about the fermentation process. Even for soil analysis, also Hydrometers are used. Interesting, isn’t it?
Summary: What Is the Density of Water?
So we have come to an end. Let’s summarize what we have discussed so far in this blog. Water density is rounded to 1000 kg/m3 in SI unit or 1 g/cm3 in CGS unit unless you need an exact value or are inclined towards the accuracy of conducting a lab or any other Science experiment in extreme temperatures. And, as I said, the density of water changes depending on the temperature and pressure, both. So if you’re experimenting with a temperature close to the water’s freezing or boiling point, you’ll need to consider using a different value and take into account the change in density. And, can you tell if ice and steam are denser than water or less dense than water? Well, the answer will be less.
The equation for density is mass by volume, i.e., ρ=m/v.
To measure the density of any substance, regular or irregular, check how much liquid is displaced by that object. For a regularly shaped object, find its volume and proceed. But, if it’s an irregular object, measure the volume of water or the liquid and how much water/ liquid an irregular object displaces in a graduated cylinder. And the last one is to use a hydrometer to measure the density of a liquid. Hope this blog will help you understand all about the density of water and how to measure the density of water or any liquid easily. Feel free to send your query or drop your message in the comment section for any doubt.