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Density of any substance is mass per unit volume. This concept is able to explain some phenomenan that occur around us. Learn about few density examples in this article.
Density is a term that we use in our day to day life. The word density is not always used in a scientific sense the way we use in physics and chemistry. For example, if there are too many trees in a forest and they are close to each other then we say that the forest is dense. Similarly, a car parking lot can be dense or less dense depending on a number of cars being parked there.
Again from a scientific point of view concept of density is very important. It is used in various experiments of physics and chemistry where precise measurement of the density of a substance is required to carry out necessary calculations.
From density formula, if we have the knowledge of mass and volume of a substance we can easily calculate its density as density is defended as mass per unit volume.
In this article, we will not concern us about how to find density and about calculating density. Here we would rather look at density examples where we have applied the concept of density to explain some phenomenon around us.
The density of any material also depends on its temperature for example if we continuously heat iron it can change its state. It takes extremely high temperatures to change iron from solid to liquid. Now when iron changes from solid to liquid its density also changes with the increase in temperature. So, the increase in temperature of a substance usually results in a decrease in its density and decrease in density results in increased volume.
Density is also affected by pressure and this dependence is most pronounced in gaseous states. When we increase pressure on say, gas in a container, its volume decreases thereby decreasing its volume.
Density difference has profound effects in phenomenon deriving the world around us. For instance, take an example of monsoon in India. We know that the process of convection is responsible for the occurrence of monsoons. But it is the difference in temperature and density characteristics of air passing over the land surface and water bodies.
Given below are some of the examples of density.
The density of oil and water explanation
Have you ever tried mixing oil with water? If you try to mix them then denser one falls at the bottom and lighter one floats above the denser liquid.
In the case of oil and water, oil floats above water when we try to mix them.
This happens because the density of water is $\text{1gm/c}{{\text{m}}^{3}}$ which is higher than that of oil. (density of vegetable oil is 0.93 $\text{gm/c}{{\text{m}}^{3}}$)
Due to this fact that oil does not dissolve in water, it makes cleanups possible after large oil spills in sea water. Such cleanup system involves the scraping or skimming the top layer of oil off the ocean’s surface.
Another such example can be seen in salad dressing where oil and vinegar do not mix together as vinegar is denser than oil.
Why do helium balloons float in the air?
You might have seen hawkers selling balloons that float in the air. Now the question is what makes these balloons float in the air. When the balloons we fill with air using a pump does not float in the air. The answer lies in the difference in densities of matter used to fill these balloons.
The balloon that floats in the air is filled with a gas called helium. That is why these balloons are also called helium balloons. Now this helium gas less dense than the air around it. This difference is the density of helium. gas and air around it make it float in the air.
One side note:- Air around us consists of nitrogen and oxygen molecules which are heavy as compared to helium molecules. Hydrogen is even lighter than helium but we do not fill balloons with hydrogen because it is highly flame able.
Floating ice cubes in water
While drinking cold beverages with ice you must have noticed that ice cubes float. If you put ice inside a glass filled with water than you could notice that ice cubes float in water. This is because water is one of the few substances that is lightly denser in its liquid form as compared to its solid form which is Ice.
Icebergs floating in ocean water
We have already established that with the decrease in temperature, ice floats in water. Icebergs also float in the ocean.
Icebergs are made of fresh water, and they also contain lots of air. They have trapped air bubbles inside them. Oceans, as we all know, are salty and have a density slightly higher than fresh water. This is the reason why icebergs that are frozen and are made up of fresh water, float.