Class 9 Science- Chapter 1- Matter In Our Surroundings – Activity 1.9: Investigating the Properties of Solids Like Definite Shape and Incompressibility

Activity 1.9: Investigating the Properties of Solids Like Definite Shape and Incompressibility

Objective

To observe the physical properties of solids such as their definite shape, boundaries, volume, and incompressibility.

Materials Needed

• A pen.
• A book.
• A needle.
• A piece of wooden stick.
• A hammer (optional).

Steps to Perform the Activity

1. Collect the above-mentioned items and place them on a flat surface.
2. Using a pencil, trace the outline of each object to record their shapes.
3. Try compressing each item by pressing them firmly with your hand or attempting to change their shape.
4. Use a hammer to test if the objects can be reshaped or broken under force.
5. Record your observations for each item.

Observations

1. Definite Shape:
   Each solid object maintains its distinct shape. For example, the pen, book, needle, and wooden stick have a fixed and unchanging shape.
2. Boundaries and Volume:
   The objects have clear boundaries and occupy a specific volume, which does not change under normal conditions.
3. Incompressibility:
   None of the objects can be compressed using hand pressure, indicating that solids resist compression.
4. Breakage Under Force:
   When hammered, some objects like the wooden stick may break, but their pieces still retain a definite shape and volume.

Also Check – Chapter 1 -MATTER IN OUR SURROUNDINGS -Class 9 – Simplified notes

Concepts Behind the Activity

1. Particle Arrangement in Solids:
   • The particles in solids are tightly packed in a fixed, orderly arrangement.
   • These particles do not move freely and are held together by strong forces of attraction.
2. Properties of Solids:
   • Definite Shape: The fixed positions of particles give solids their definite shape.
   • Fixed Volume: Tightly packed particles ensure that solids have a constant volume.
   • Incompressibility: The lack of space between particles makes solids nearly incompressible.
3. Rigidity of Solids:
   • Solids resist external forces and maintain their shape unless the force is extreme (e.g., hammering).

Learning Outcomes

1. Physical Properties of Solids:
   Solids have a definite shape, volume, and boundaries, which distinguish them from liquids and gases.
2. Incompressibility:
   Solids cannot be compressed easily because their particles are packed closely together.
3. Applications of Solid Properties:
   These properties make solids ideal for structures, tools, and other objects that require rigidity and stability.

Examples to Consider

1. A rubber band is considered a solid because, although it can change shape when stretched, it returns to its original shape when the force is removed.
2. A sponge appears compressible but remains a solid because its shape is restored after releasing the pressure due to trapped air in its holes.
3. Salt or sugar crystals are solids even though they take the shape of their container; their individual particles have a fixed shape.

Intext and additional Question Answers on Activity 1.9: Investigating the Properties of Solids Like Definite Shape and Incompressibility

Question 1: Do all solids (pen, book, needle, wooden stick) have a definite shape, distinct boundaries, and a fixed volume?

Yes, solids maintain a definite shape and fixed volume because their particles are tightly packed in a fixed arrangement.

Question 2: Are solids capable of diffusing into each other?

No, under normal conditions, solids do not diffuse into each other because their particles are held in fixed positions.

Question 3: Can solids be compressed?

Solids are nearly incompressible because their particles are closely packed with little to no space between them.

Additional Question 1: Why does a sponge compress if solids are incompressible?

A sponge has tiny air pockets. When compressed, the air is pushed out, causing it to change shape. However, the sponge material itself remains solid and incompressible.

Additional Question 2: Can sugar crystals be called solids even if they take the shape of a container?

Yes, sugar crystals are solids. They have a definite shape and volume individually. They appear to take the shape of a container because they are loosely packed, not because they lose their solid properties.

Conclusion

This activity demonstrates that solids are rigid, have a definite shape and volume, and are incompressible under normal conditions. These properties are due to the fixed arrangement and strong attraction between their particles, which make them distinct from liquids and gases.