Activity 1.6, 1.7, 1.8 Explanation NCERT Science Class 9 Matter In Our Surroundings
Activity 1.6 asks us to join hand to hands in various fashion to form different groups and try to break this group.
Friends in idu-Mismi are the hardest to break.
This experiment is an illustration of how molecules of a particle are joined with each other. Molecules in a substance are joined to other molecules by the forces of attraction. This force of attraction keeps them together. If the force is very high, these particles are solid at room temperature; while if this force is low particles are in gaseous form.
Activity 1.7 asks us to break, cut or stretch various pieces of an iron nail, chalk, and a rubber band.
- Hammering a piece of the iron nail does not break the nail but flatten its surface.
- Hammering chalk breaks the chalk and gives us powdered chalk.
- We can stretch the rubber band to a large length without any break.
Force of attraction between molecules of different substances is different.
In activity 1.6 we saw that force of attraction between solid, liquid and gases is different. This experiment focuses on the force of attraction between different solids. Here all the particles are solid, but the force of attraction between their molecule is different. In iron nail force of attraction is the highest. The force of attraction in chalk is lower, so breaking them into pieces is easy.
Rubber contains a long chain of molecules linked to each other by covalent bonds. This long chain structure gives them high elasticity.
Activity 1.8 asks us to cut water using fingers and examine why water joins again.
We can easily cut the water using fingers. Water join again once we remove the finger.
Water has a weak attraction force than solids, so we can easily swirl our fingers across it. Once we move the finger, water occupies the same space again. A Similar process also occurs with air; here air molecules regain the empty spaces similarly.