Physical Nature of Matter
1. Matter is Made Up of Tiny Particles
- All substances, whether solids, liquids, or gases, are made up of extremely small particles.
- These particles are so tiny that they cannot be seen with the naked eye.
- Even though an object appears continuous, if we zoom in using a microscope, we can see that it is made of discrete particles.
Example:
- When we dissolve a spoonful of sugar in water, the sugar seems to disappear, but it is actually breaking into tiny particles that spread throughout the water.
2. Evidence of the Existence of Particles
(A) Diffusion: Mixing of Substances
Definition:
Diffusion is the process where particles move from a region of higher concentration to a region of lower concentration without any external force.
Explanation:
- Since matter is made of tiny particles that are constantly moving, they naturally mix when brought together.
- The speed of diffusion depends on the state of matter (faster in gases, slower in liquids, slowest in solids).
Examples:
- Perfume spreading in a room: When perfume is sprayed in one corner, its fragrance spreads throughout the room. This happens because the tiny gas particles of the perfume mix with air particles and move around.
- Ink spreading in water: When a drop of ink is added to water, the ink particles move and spread evenly, showing that both ink and water are made of moving particles.
- Mixing of gases in the atmosphere: Oxygen, nitrogen, and carbon dioxide mix naturally without stirring due to diffusion.
(B) Dissolution: Sugar Dissolving in Water
Definition:
Dissolution is the process where solid particles break down and spread throughout a liquid, making a uniform mixture.
Explanation:
- When sugar is added to water and stirred, the sugar particles break into extremely tiny particles that spread into the spaces between water molecules.
- Even though we cannot see the sugar anymore, we can still taste it, proving that the sugar particles are present in water.
Examples:
- Salt dissolving in water: The salt particles fit into the gaps between the water molecules and spread evenly.
- Gas dissolving in water: Oxygen dissolves in water, allowing fish and other aquatic animals to breathe.
3. Properties of Particles of Matter
(A) Particles Have Space Between Them
Explanation:
- The particles of matter are not tightly packed together; there is always some space between them.
- This space is called intermolecular space.
- The amount of space varies in different states of matter:
- Solids: Very little space (particles packed closely).
- Liquids: More space than solids (particles can slide past each other).
- Gases: Large spaces (particles move freely).
Example:
- Sugar dissolving in water: The sugar particles occupy the spaces between water molecules, which is why the water level does not increase significantly.
(B) Particles Are Constantly Moving
Explanation:
- The particles of matter are in continuous motion, known as Brownian motion.
- They have kinetic energy, which increases with temperature.
- This motion is responsible for diffusion and dissolution.
Examples:
- Perfume spreading in a room: Gas particles move randomly in all directions, spreading the smell.
- Boiling water: As water is heated, particles move faster and escape as steam.
- Floating dust particles: Tiny dust particles in the air move randomly due to collisions with air molecules.
(C) Particles Attract Each Other
Explanation:
- Particles of matter experience a force of attraction that holds them together.
- This force is called intermolecular force and varies in different states of matter:
- Solids: Strongest attraction (fixed shape).
- Liquids: Moderate attraction (can flow).
- Gases: Weakest attraction (move freely).
Examples:
- Iron rod vs. Water: A solid iron rod does not break easily because of strong particle attraction, whereas water flows because of weaker attraction.
- Rubber band stretching: The force of attraction is strong but flexible.
Properties of Particles of Matter
1️⃣ Particles Have Space Between Them
- Explanation: The amount of space between particles varies in different states of matter.
- Example: Sugar dissolving in water as particles fit into empty spaces.
2️⃣ Particles Are Constantly Moving
- Explanation: They possess kinetic energy and move randomly.
- Example: Dust particles floating in air, perfume spreading in a room.
3️⃣ Particles Attract Each Other
- Explanation: The strength of attraction differs in different states of matter.
- Example: Iron has a strong force of attraction, while gases have weak attraction.