🌍 Chapter 1: Matter in Our Surroundings
(Class 9 Science – NCERT Notes)
📚 Introduction
Everything around us—air, water, buildings, plants, and even we ourselves—is made of matter. Matter is anything that occupies space and has mass. Scientists have studied its properties and behavior for centuries. This chapter explores the physical nature of matter, its characteristics, states, and changes in different conditions.
✨ 1. Physical Nature of Matter
🔹 1.1 Matter is Made Up of Tiny Particles
✅ Matter is not continuous but made up of very small particles.
✅ These particles are so tiny that they cannot be seen with the naked eye.
✅ 🧪 Experiment:
- Dissolve sugar/salt in water → Water level does not increase!
- This proves that matter is made of particles and that there are spaces between them.
🔹 1.2 How Small Are These Particles?
✅ 🧪 Experiment:
- Take a potassium permanganate crystal and dissolve it in water.
- Keep diluting it further, and the color remains visible!
- This shows that even a small particle contains millions of smaller particles.
💡 Quick Trick: Imagine cutting a piece of chalk into the tiniest bits—you’ll still have chalk particles!
🔥 2. Characteristics of Particles of Matter
🔸 2.1 Particles Have Space Between Them
📌 Particles of matter are not tightly packed and have spaces between them.
📌 This is called intermolecular space.
📌 🧪 Example: Dissolving sugar in water → Sugar particles fit into the spaces between water molecules.
💡 Easy Trick: Think of a glass full of pebbles—if you pour sand over it, the sand fills the gaps. This is just like sugar in water!
🔸 2.2 Particles are Always Moving
📌 Particles of matter are in constant motion and have kinetic energy.
📌 As temperature increases, the movement of particles increases.
📌 🧪 Examples:
- The smell of perfume spreading in a room.
- Ink spreading in water.
💡 Trick to Remember: Higher temperature = Faster movement of particles! 🌡️💨
🔸 2.3 Particles Attract Each Other
📌 Particles exert forces of attraction, which keeps them together.
📌 Strength of attraction:
- 💎 Strongest in solids (tight packing).
- 💧 Weaker in liquids (flow easily).
- 💨 Weakest in gases (move freely).
💡 Memory Hack:
🧊 Ice → 💦 Water → 💨 Steam (Particles get farther apart as attraction decreases).
⚡ 3. States of Matter
Matter exists in three states:
| 💎 Solid | 💧 Liquid | 🌫️ Gas |
|---|---|---|
| Fixed shape & volume | No fixed shape, but fixed volume | No fixed shape, no fixed volume |
| Strong attraction | Moderate attraction | Weak attraction |
| Does not flow | Flows easily | Flows & spreads everywhere |
💡 Super Trick to Remember:
SOLid = SOLid shape
LIQuid = LIQuid shape (takes container’s shape)
GAS = GASes spread freely
🔄 4. Can Matter Change Its State?
🔥 4.1 Effect of Temperature on Matter
📌 Heating increases kinetic energy, causing particles to move faster.
📌 If heated enough, particles overcome attraction and change state.
| 🌡️ Change | 🔁 Process |
|---|---|
| Solid → Liquid | Melting (Fusion) |
| Liquid → Gas | Boiling (Vaporization) |
| Gas → Liquid | Condensation |
| Liquid → Solid | Freezing (Solidification) |
| Solid → Gas | Sublimation |
💡 Example: Ice → Water → Steam (When heated)
💡 Quick Hack: “MBCFS” = Melting, Boiling, Condensation, Freezing, Sublimation.
🔄 4.2 Effect of Pressure on Matter
📌 Applying pressure compresses gases into liquids.
📌 Example: LPG (Liquefied Petroleum Gas) in gas cylinders.
💡 Trick: More pressure = More compact particles! 🏋️♂️
💦 5. Evaporation
💨 5.1 What is Evaporation?
📌 Definition: The process by which a liquid turns into a gas below its boiling point.
📌 Example: Water from wet clothes dries up due to evaporation.
🌬️ 5.2 Factors Affecting Evaporation
| Factor | Effect on Evaporation |
|---|---|
| 🌡️ Temperature | Higher temp = Faster evaporation |
| 📏 Surface Area | More area = Faster evaporation |
| 🌬️ Wind Speed | More wind = Faster evaporation |
| 💧 Humidity | More humidity = Slower evaporation |
💡 Example: Sweat evaporates faster in hot weather with wind but slower on humid days.
❄️ 5.3 How Does Evaporation Cause Cooling?
📌 Evaporation absorbs heat from the surroundings, making things cooler.
📌 Examples:
- We feel cool after sweating.
- Water in an earthen pot stays cool in summer.
💡 Quick Memory Trick:
Evaporation → Absorbs Heat → Cooling Effect ❄️
📝 Key Terms to Remember
| Term | Definition |
|---|---|
| Matter | Anything that has mass and occupies space |
| Intermolecular Space | Space between particles |
| Kinetic Energy | Energy due to movement of particles |
| Melting Point | Temperature at which a solid melts into a liquid |
| Boiling Point | Temperature at which a liquid boils into gas |
| Sublimation | Direct conversion of solid into gas |
| Evaporation | Slow conversion of liquid into gas |
🎯 Conclusion
Matter exists in different states and can change from one state to another with temperature and pressure. The properties of matter are based on the behavior of particles in different conditions.
🏆 Exam Tips & Tricks!
✔ Matter is made up of tiny particles – Proved by dissolving substances in water.
✔ Particles of matter move continuously – Proved by diffusion of perfume.
✔ Evaporation causes cooling – That’s why we feel cool after sweating!
✔ Pressure can liquefy gases – That’s how LPG & CNG are stored.
✔ Solid → Liquid → Gas → Reverse process exists too!
🧠 Quick Revision Mnemonics:
🌀 MBCFS → Melting, Boiling, Condensation, Freezing, Sublimation
🔥 Gases Spread Freely!
💦 Evaporation = Cooling Effect