Water is a daily necessity. We cannot imagine a life without water. Be it to control our thirst, or to cook food, or to clean our home and clothes, or to bathe, water is required everywhere. Water is the most important thing for life on Earth.
But have you ever thought about different features or properties of water??
Why does a paper boat floats in water but an iron needle sinks, even an iron ship floats in water. Why does this take place? Have you ever thought about it??
Well, the answer is density
Contents
DENSITY? What’s that??
It is the amount of mass contained per unit volume.
- anything denser than water sinks in water and anything lighter than water floats on it.
- But what happens to iron needle and iron boat? While both are made of the same material, ship is heavier than needle, still a ship floats and the needle sinks?
The reason is air
Air?
Yes air. An iron needle is compact, not having any air but only iron and thus it’s density is more than water. But an iron ship has lots of air in it and air being lighter than water makes a ship float on it. This is why a ship sinks when water enters the ship.
Let’s talk about another experiment to demonstrate density
- Put some salt in a container filled with water.
- Now add some lemon pieces to it
What do you see? Do the lemon pieces float on it or sink?
Well the lemon pieces float on it.
But why? Lemon is definitely heavier than water then why it didn’t sink?
The reason behind this is when salt is added to water, it increases its density and thus lemon floats on a salted water. Same thing happens with eggs. When we boil eggs, we add some salt to the boiling water which increases its density and the eggs don’t sink completely in water.
This is the reason why no one drowns in Dead Sea. It has plenty of salt content in it. Even a person can lie straight and keep floating on dead sea.
What dissolves and what not?
Anything which is soluble in water dissolves in it.
For example, if we add some sugar or salt to water and stir it a little or leave it for a while, it will dissolve in it. Meanwhile if we add chalk powder or soil or oil in water, it will not dissolve in it.
Chalk and soil will get collected at the bottom of the water container forming a sediment, whereas oil will form tiny droplets in the water itself. This is due to viscosity (you’ll learn about this in higher classes)
Water is an essential part of life. Different questions can be raised every second while using water because it has so many different properties.