Class 9 Science - Chapter 1

Cheatsheet Content

### Matter: Definition & Classification - **Definition:** Anything that occupies space and has mass. Made up of tiny particles. - **Early Indian Philosophers:** Classified matter into "Panch Tatva" (air, earth, fire, sky, water). - **Modern Classification:** Based on physical properties (in this chapter) and chemical nature (subsequent chapters). ### Physical Nature of Matter #### Matter is Made Up of Particles - **Activity 1.1 (Salt/Sugar in Water):** Shows particles of salt/sugar get into spaces between water particles. - **Activity 1.2 (Potassium Permanganate Dilution):** Demonstrates that particles of matter are extremely small and can divide repeatedly. Even after many dilutions, color is visible, indicating millions of particles in a single crystal. #### Characteristics of Particles of Matter 1. **Particles of Matter Have Space Between Them:** - Evident from dissolving salt/sugar in water (Activity 1.1). - Particles of one substance get into the spaces of another (e.g., tea, coffee). 2. **Particles of Matter Are Continuously Moving:** - **Kinetic Energy:** Particles possess kinetic energy; temperature increase leads to faster movement and higher kinetic energy. - **Activities:** - **1.3 (Incense Stick):** Smell spreads due to moving particles. - **1.4 (Ink/Honey in Water):** Particles intermix due to continuous motion. - **1.5 (Copper Sulphate/KMnO4 in Hot/Cold Water):** Diffusion is faster in hot water, showing increased kinetic energy with temperature. - **Diffusion:** Intermixing of particles of two different types of matter on their own. Faster on heating. 3. **Particles of Matter Attract Each Other:** - **Activities:** - **1.6 (Human Chains):** Different strengths of attraction (locked arms > holding hands > fingertips). - **1.7 (Iron Nail, Chalk, Rubber Band):** Varying forces of attraction make them break differently. - **1.8 (Cutting Water):** Water surface remains together due to attractive forces. - The strength of this force varies from substance to substance. ### States of Matter Matter exists in three states: solid, liquid, and gas, due to variations in particle characteristics. #### 1. The Solid State - **Activity 1.9 (Pen, Book, Needle):** - **Properties:** Definite shape, distinct boundaries, fixed volume, negligible compressibility, rigid (resist change in shape). - **Examples:** - **Rubber band:** Changes shape under force but regains it (solid if it breaks under excessive force). - **Sugar/Salt:** Individual crystal shape is fixed, even if they take the shape of the container. - **Sponge:** Compressible due to air trapped in minute holes. #### 2. The Liquid State - **Activity 1.10 (Water, Oil, Milk):** - **Properties:** No fixed shape (takes container shape), fixed volume, flows easily (fluid), not rigid. - **Diffusion:** Solids, liquids, and gases can diffuse into liquids. Rate of diffusion in liquids is higher than in solids due to free movement and greater space between particles. - **Aquatic Life:** Dissolved oxygen and carbon dioxide are essential for aquatic animals and plants. #### 3. The Gaseous State - **Activity 1.11 (Syringes with Air, Water, Chalk):** - **Compressibility:** Gases are highly compressible (e.g., LPG, CNG) due to large spaces between particles. - **Diffusion:** Diffuse very fast into other gases due to high particle speed and large spaces (e.g., smell of food). - **Particle Movement:** Particles move randomly at high speed, hitting each other and container walls. - **Pressure:** Exerted by gas particles per unit area on container walls. - **Magnified Schematic (Fig. 1.5):** Illustrates particle arrangement and motion in solids, liquids, and gases. - **Density:** Mass per unit volume. Solids generally have higher density than liquids, but ice floats on water (an anomaly due to its structure). ### Can Matter Change its State? Matter can change state by altering temperature or pressure. #### 1. Effect of Change of Temperature - **Activity 1.12 (Heating Ice to Water to Vapor):** - **Melting:** Solid to liquid. - **Melting Point:** Minimum temperature at which a solid melts at atmospheric pressure (e.g., ice = 273.15 K). - **Fusion:** Process of melting. - **Latent Heat of Fusion:** Heat energy required to change 1 kg of solid to liquid at its melting point without temperature change. Energy is used to overcome forces of attraction between particles. - **Boiling/Vaporisation:** Liquid to gas. - **Boiling Point:** Temperature at which a liquid starts boiling at atmospheric pressure (e.g., water = 373 K). - **Latent Heat of Vaporisation:** Heat energy required to change 1 kg of liquid to gas at its boiling point without temperature change. - **Kelvin Scale:** SI unit of temperature. 0°C = 273.15 K (approx. 273 K). - **Sublimation:** Direct change from solid to gas without liquid state. - **Deposition:** Direct change from gas to solid without liquid state. - **Activity 1.13 (Camphor/Ammonium Chloride):** Demonstrates sublimation. #### 2. Effect of Change of Pressure - **Activity 1.14 (Compressing Gas in Syringe):** Gases are highly compressible. - **Liquefaction:** Applying pressure and reducing temperature can liquefy gases. - **Solid CO2 (Dry Ice):** Stored under high pressure; converts directly to gas at 1 atmosphere pressure (deposition). - **Conclusion:** Pressure and temperature determine the state of a substance. ### Evaporation - **Definition:** Phenomenon of change of a liquid into vapours at any temperature below its boiling point (surface phenomenon). - **Factors Affecting Evaporation (Activity 1.14):** 1. **Surface Area:** Increase in surface area increases evaporation rate (e.g., spreading clothes). 2. **Temperature:** Increase in temperature increases evaporation rate (more particles gain kinetic energy). 3. **Humidity:** Decrease in humidity increases evaporation rate (less water vapor in air). 4. **Wind Speed:** Increase in wind speed increases evaporation rate (water vapor particles move away with wind). - **Evaporation Causes Cooling:** Particles absorb energy from surroundings to regain energy lost during evaporation, making surroundings cold (e.g., acetone on palm, sprinkling water on roof). - **Cotton Clothes in Summer:** Cotton absorbs sweat and exposes it to atmosphere for easy evaporation, leading to cooling. - **Water Droplets on Cold Glass:** Water vapor in air loses energy on contact with cold glass, condenses into liquid droplets. ### More to Know: States of Matter - **Five States:** Solid, Liquid, Gas, Plasma, Bose-Einstein Condensate. - **Plasma:** Super energetic, super excited, ionized gas particles (e.g., fluorescent tubes, neon signs, stars). - **Bose-Einstein Condensate (BEC):** Formed by cooling extremely low-density gas to super-low temperatures. Predicted by Albert Einstein based on Satyendra Nath Bose's calculations.