Solution to Activity 1.9 of NCERT Class 9 Science Chapter 1 Matter in Our Surroundings –

Answer:

Aim: To apply the instructions in case of the pen, book, needle and piece of wooden stickand conclude based on the observations.

Materials Required: A pen, a book, a needle and a piece of wooden stick.

Procedure:

(i) Sketch the shape of the given articles in your notebook by tracing a pencil around them. Note the observations.

(ii) Note what happens if they hammered with an object, pulled with your hands or dropped from a height.

(iii) Try to press them against each other to see if they can diffuse into each other.

(iv) Apply force on them and see if they compress.

Observations:

• The objects have definite shape and distinct boundaries as shown below:

• They have a fixed volume.
• If they are hammered, pulled or dropped they might break, but they maintain their shape.
• They are not capable of diffusing into each other.
• They cannot be compressed under application of force.

Conclusions:

• Solids have definite shape, distinct boundaries and fixed volumes.
• They tend to maintain their shape and are not compressible. Therefore, they are rigid.
• The above phenomena are due to the high force of attraction between solid particles which keep them bound tightly to one another.