In our daily life whatever we see around is Matter. But is matter around us pure? A matter is defined as something which occupies space and has mass. Mass is a fundamental property which shows the amount of substance in an object.
How can we define the term purity? Many times we would have come across sentences like this water is pure or the milk used in making this tea is pure. Is this right? What is the basis for saying that a substance is pure? Can we say any substance is pure if it is smooth or soft or it is white? NO.
According to scientists, a substance is said to be pure if we take a substance and put it at a place and pick a particle from one corner and another particle from some random corner we get the identical particle despite the number of attempts made. In other words, a pure substance is made up of only one kind of elements or molecules. But if a substance is composed of different kind of elements or molecules then that substance is known as an impure substance. For example: When we were children, we would have played playpen with balls in which we have a large number of small balls. In this, we can have different colours of balls or all the balls can be of the same colour. If all the balls are of the same colour, then we can pick two balls from anywhere and it will be identical. This type of substance in which if we pick particles from any corner of the substance and it is same, then it is pure substance. But if the balls are of different colours in the playpen, then now if we pick balls from different corner they will not be identical always. This case in which if we pick particles from some random corners and are not identical then it is known as impure substance. The impure substance are often known as mixture.
Characteristics of pure substance:
- They are perfectly homogeneous in nature.
- They are made up of only one kind of atoms or molecules.
- They have fixed composition.
- It have fixed density, melting point and boiling point etc.
Characteristics of impure substance:
- It does not have any specific properties, the properties of mixture are result of the average of properties of all the constituents.
- It is formed as a result of physical change.
- They have variable composition.
- The mixtures are homogeneous as well as Heterogeneous Mixture in nature.
This was just a glimpse about matter and its type, on the basis of its composition. More details about this topic would be understood by solving sample questions and answers here NCERT solutions for is matter around us pure.