Materials and objects

Ghulan and Sheeta are back in class after the summer break, showing each other their new notebooks and a new pen. Their science teacher, Madam Vidya, asks them to look closely at the things they use every day. How are they alike? How are they different? What shapes and colours are they? How do they feel? Are some heavier than others?

Everything is made of something: paper, wood, cloth, glass, metal, plastic, clay. Any substance used to make an object is called a material. The notebook is the object; paper is the material it is made of. A chair is an object; wood is its material.

One object can be made of several materials. A pen may have a plastic body, a metal nib and ink inside. A bottle can be made of plastic, glass, steel or clay.

One material can make many objects. Think how many things are made of plastic, or of wood: chairs, tables, pencils, rulers and boxes.

How do we choose? By the purpose of the object and the properties of the material. A soft stress ball you squeeze in your hand is made of sponge; a cricket ball, hit hard again and again, is made of hard leather. A tumbler must hold water, so it can be glass or metal, but not cloth: water would soak through the cloth and leak out. For the same reason, paper-like materials would make poor cooking pots.