Matter in Our Surroundings – Long Answer Questions

Medium Level (Application & Explanation)

Answer:

In a solid, particles are closely packed and held by strong forces.
They vibrate at their place but do not move freely.
So, solids have definite shape and definite volume. Example: ice, wood.
In a liquid, particles are close, but forces are weaker than in solids.
They can slide past each other. So liquids have no fixed shape but a fixed volume. Example: water, oil.
In a gas, particles are far apart and move randomly.
Forces are very weak, so gases have no fixed shape and no fixed volume. Example: air, oxygen.

Answer:

On heating, particles gain kinetic energy and vibrate faster.
In a solid, rising energy weakens attractive forces and particles start to break free.
At the melting point, the solid changes to a liquid.
In the liquid, further heating speeds up particles, letting more escape to the surface.
At the boiling point, particles leave the liquid throughout the bulk to form a gas.
In the gas, particles are far apart and move rapidly in all directions.
The chemical composition does not change. It is a physical change.

Answer:

Evaporation is when a liquid turns into gas at the surface, even below boiling point.
Higher temperature gives particles more energy. So more particles escape. Example: puddles dry faster at noon.
Greater surface area exposes more particles to air. Example: water in a wide plate evaporates faster than in a glass.
Lower humidity (drier air) allows more particles to escape. Example: clothes dry faster in dry weather.
Evaporation causes cooling because high-energy particles leave first.
It is a slow process and happens only at the surface.

Answer:

Solids: Definite shape and definite volume. Particles are very close.
Motion is only vibration. Forces of attraction are strong.
Liquids: No fixed shape, but definite volume. Particles are close but can slide.
Motion is random but limited. Forces are moderate.
Gases: No fixed shape and no fixed volume. Particles are far apart.
Motion is rapid and random. Forces are very weak.
These differences explain compressibility, flow, and container shape behavior.

Answer:

On cooling, particles lose energy and move slower.
Attractive forces become stronger and pull particles closer.
A gas changes to a liquid by condensation. Example: water drops on a cold bottle surface.
A liquid changes to a solid by freezing. Example: water turning to ice in a freezer.
These are physical changes. The substance remains the same.
Cooling reduces kinetic energy, which helps in forming stronger bonds between particles.

Answer:

The spread-out towel dries faster due to larger surface area.
More surface means more particles at the top can escape to the air.
Evaporation happens at the surface, not deep inside the cloth.
The folded towel traps moist air inside, increasing local humidity.
Higher humidity slows evaporation because fewer water particles can escape.
In both cases, room temperature is same, so surface area and humidity make the difference.
The faster drying is due to greater exposure to air and lower moisture around the surface.

Answer:

At noon, the temperature is higher.
Higher temperature gives particles more kinetic energy to escape the liquid.
In the evening, temperature falls, so particles have less energy to leave.
On a humid day, the air already has a lot of water vapor.
High humidity reduces the rate at which new particles can escape.
So, evaporation is fastest when it is hot and dry, and slower when it is cool or humid.
The puddle size changes reflect the energy and air moisture conditions.

Answer:

Perfume releases gas particles into the air.
Gas particles are far apart and move randomly with high speed.
They mix quickly with air due to their constant motion and large space between particles.
Syrup is a liquid with particles that are closer and move slowly.
It spreads only by flowing and surface spreading, which takes time.
So, due to particle spacing and speed, perfume spreads faster than syrup.
This shows how the state of matter affects the rate of spreading.

Answer:

As you push, the volume inside the syringe becomes smaller.
Gas particles get closer, but they still move randomly.
The number of collisions with the walls increases, so pressure rises.
This shows gases are compressible due to large spaces between particles.
If you release the plunger, particles spread out and the gas expands.
This behavior contrasts with liquids and solids, which are not easily compressed.
It highlights weak attractive forces and large interparticle space in gases.

Answer:

At 60°C, water changes to gas by evaporation at the surface only.
Evaporation happens below the boiling point and is slow.
It needs no bubbles, and the rate depends on temperature, surface area, and humidity.
At 100°C, water changes to gas by boiling throughout the liquid.
Boiling is rapid, forms bubbles, and happens at a fixed temperature for that pressure.
Both are physical changes, and the substance remains water.
The key differences are the location (surface vs bulk) and the speed of the process.