Gonit Vigyan

 

Chapter 01: Matter in Our Surroundings 

Definition of Matter:

• Everything around us is made up of matter.

• Examples: air, food, stones, clouds, stars, plants, animals, water droplets, sand particles, etc.

Characteristics of Matter:

• Has mass and occupies space (i.e., has volume).

• Exists in various shapes, sizes, and textures.

Ancient Understanding:

• Early Indian Philosophers:

  • Classified matter into five basic elements (Panch Tatva):

    • Air, Earth, Fire, Sky, Water

  • Believed that everything (living or non-living) is made of these elements.

• Ancient Greek Philosophers:

  • Had a similar classification of matter.

Modern Classification:

• Scientists classify matter in two ways:

  1. Based on physical properties

  2. Based on the chemical nature

• This chapter focuses on classification based on physical properties.

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1.1 Physical Nature of Matter

1.1.1 Matter is Made Up of Particles

• Two early beliefs about matter:

  • Matter is continuous (like a block of wood).

  • 

  • Matter is made of particles (like sand).

    
    
    

Activity 1.1:

• Steps:

  • Fill half of a 100 mL beaker with water and mark the level.

  • Add salt/sugar and stir with a glass rod.

  • Observe any change in water level.

• Observation:

  • Salt/sugar disappears, yet water level remains the same.

• Conclusion:

  • The particles of salt/sugar occupy the spaces between water particles.

  • This shows that matter is made up of particles.

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1.1.2 How Small are These Particles of Matter?

Activity 1.2:

• Steps:

  • Dissolve 2-3 crystals of potassium permanganate in 100 mL water.

  • Take 10 mL of this solution and add to 90 mL clear water.

  • Repeat dilution 5 to 8 times.

• Observation:

  • The colour remains visible even after many dilutions.

• Conclusion:

  • A few crystals can colour about 1000 L of water.

  • Matter is made up of extremely small particles that continue to divide into smaller units.

  • This activity proves:
    ➤ Particles of matter are very small — beyond imagination.

• Alternate activity: Use 2 mL of Dettol – its smell is detectable even after repeated dilutions.

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Important notes : 

Units of Mass and Volume

• SI Unit of Mass:
  ➤ Kilogram (kg)

• SI Unit of Volume:
  ➤ Cubic metre (m³)

• Common Units of Volume:
  ➤ Litre (L) is commonly used.

• Conversions:

  • 1 L = 1 dm³

  • 1 L = 1000 mL

  • 1 mL = 1 cm³

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1.2 Characteristics of Particles of Matter

1.2.1 Particles of Matter Have Space Between Them

• Observation from Activities 1.1 & 1.2:

  • When substances like salt, sugar, Dettol, or potassium permanganate are added to water, they evenly mix without increasing the water level.

• Examples:

  • Making tea, coffee, or lemonade also shows that different substances mix well.

• Conclusion:

• This proves that particles of matter have empty spaces between them.

• Particles of one substance occupy the spaces between particles of another

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1.2.2 Particles of Matter Are Continuously Moving

Activities and Observations:

Activity 1.3: Incense Stick

• Unlit stick: Smell detected only when very close.

• Lit stick: Smell spreads and is detectable from a distance.

• Conclusion: Particles of the fragrance move through air.

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Activity 1.4: Ink and Honey in Water

• Ink drop: Begins to spread immediately, even without stirring.

• Honey: Spreads more slowly.

• Conclusion:

  • Particles are in motion.

  • Lighter particles (like ink) diffuse faster than heavier ones (like honey).

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Activity 1.5: Crystal in Hot and Cold Water

• Crystals dissolve faster in hot water than in cold water.

• Diffusion is quicker with heat.

• Conclusion:

  • Temperature increases particle movement.

  • Mixing is faster at higher temperatures.

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Key Concepts:

• Particles of matter are always in motion.

  • This motion is due to kinetic energy.

• Kinetic Energy Increases with Temperature:

  • As temperature rises, particles move faster.

• Diffusion:

• The intermixing of particles of two different substances on their own.

• Faster when temperature increases.

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1.2.3 Particles of Matter Attract Each Other

Activities and Observations:

Activity 1.6: Human Chain Game

• Four groups form human chains with varying grip:

  1. Locked arms (strongest bond – like Idu-Mishmi dance).

  2. Holding hands.

  3. Touching fingertips (weakest bond).

  4. Another group tries to break the chains.

• Observation:

  • Group with locked arms is hardest to break → represents strongest force of attraction.

  • Group with fingertips is easiest to break → represents weakest attraction.

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Activity 1.7: Testing Materials (Iron Nail, Chalk, Rubber Band)

• Iron nail: Hard to break → strong particle attraction.

• Chalk: Breaks easily → moderate attraction.

• Rubber band: Stretches → flexible but cohesive particles.

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Activity 1.8: Cutting Water

• Try cutting water surface with fingers → not possible.

• Reason: Particles of water attract each other and stay together, showing cohesion.

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Conclusion:

• Particles of matter attract each other.

• The strength of attraction:

  • Varies in different substances.

  • Determines hardness, flexibility, and binding of the material.

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1.3 States of Matter

1.3.1 The Solid State

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General Properties of Solids:

• Definite shape and fixed volume.

• Distinct boundaries.

• Negligible compressibility.

• Not capable of diffusion into each other.

• Rigid in nature – tend to maintain their shape under external force.

• May break under force, but do not flow or change shape easily.

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Activity Observations (1.9):

• Objects like pen, book, needle, wooden stick:

  • Have a definite shape and volume.

  • Do not get compressed easily.

  • Do not diffuse into each other.

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Special Cases (Still Considered Solids):

1. Rubber Band:

   • Can change shape when stretched.

   • Returns to original shape when force is removed.

   • Breaks if stretched excessively.

   • ✅ Still a solid.

2. Sugar and Salt:

   • Take the shape of container when poured.

   • But each crystal has a fixed shape.

   • ✅ Still solids.

3. Sponge:

   • Compressible due to air trapped in pores.

   • Air is expelled on pressing.

   • ✅ Still a solid.

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1.3.2 The Liquid State

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General Properties of Liquids:

• No fixed shape – take the shape of the container.

• Fixed volume – remains the same in different containers.

• Not rigid, but fluid – can flow easily.

• Cannot be compressed easily – compressibility is very low.

• Particles have more space between them than in solids.

• Can diffuse into other liquids or gases.

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Activity Observations (1.10):

• Liquids like water, oil, milk, juice, cold drink:

  • Spill and flow when poured.

  • Volume remains the same when measured and transferred.

  • Shape changes with the container.

  • Flow easily from one container to another.

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Diffusion in Liquids:

• Solids, liquids, and gases can diffuse into liquids.

• Rate of diffusion in liquids is higher than in solids.

• This is because:

  • Liquid particles move more freely.

  • They have greater intermolecular space than solids.

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Biological Importance of Diffusion in Liquids:

• Oxygen and carbon dioxide gases from air dissolve in water.

• Aquatic animals breathe underwater due to dissolved oxygen.

• Diffusion of gases in water is essential for life in aquatic environments.

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1.3.3 The Gaseous State

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General Properties of Gases:

• No fixed shape and no fixed volume.

• Highly compressible – can be compressed into small volumes.

• Particles are far apart and move freely and randomly at high speed.

• Gases can flow and are also classified as fluids.

• Occupy entire space of the container they are in.

• Exert pressure on the walls of the container due to constant collisions.

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Activity Observations (1.11):

• Syringe filled with gas: piston moves easily, showing high compressibility.

• Syringe filled with water or chalk: piston resists compression, showing low compressibility.

• Conclusion: Gases are much more compressible than solids or liquids.

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Examples of Compressed Gases:

• LPG (used for cooking).

• CNG (used in vehicles).

• Oxygen cylinders (used in hospitals).

These gases are stored in compressed form to reduce space and make transportation easier.

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Diffusion in Gases:

• Fastest rate of diffusion among solids, liquids, and gases.

• Particles move quickly and spread out to fill any space available.

• Example: Smell of food spreads quickly through air due to diffusion of aroma particles.

• Diffusion happens because of high kinetic energy and large intermolecular spaces.

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Pressure in Gases:

• Gas particles move randomly and collide with each other and the walls of the container.

• These collisions create pressure.

• Gas pressure = force per unit area exerted by particles on the container walls.

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 1.4 Can Matter Change its State?

• Observation: Water can exist in three different states of matter:

  • Solid: Ice

  • Liquid: Water

  • Gas: Water vapor

• Key Questions:

• What happens inside matter during a change of state?

• What happens to the particles of matter during the change of states?

• How does the change of state occur?

1.4.1 Effect of Change of Temperature

• Activity 1.12 (Heating Ice):

  • Steps:

    • Take 150g of ice in a beaker.

    • Suspend a thermometer in the ice.

    • Heat the ice and note the temperature at the following points:

      • When the ice starts melting.

      • When all the ice has turned into water.

    • Heat further until the water starts boiling and observe the temperature until most of the water vaporizes.

• Observations and Explanation:

  • Effect of Heating: As the temperature increases, the kinetic energy of the particles in the solid increases. This causes particles to vibrate more rapidly, overcoming the forces of attraction between them, leading to the solid melting into a liquid.

  • Melting Point: The temperature at which a solid melts is called its melting point. For ice, it is 273.15 K.

  • Latent Heat of Fusion: The heat energy required to change 1 kg of a solid into a liquid at its melting point is known as the latent heat of fusion. This heat energy is absorbed without causing a temperature rise, hence it is called latent heat (latent means hidden).

• Further Heating:

  • As heat is supplied to water, the particles move even faster, eventually gaining enough energy to break free from the forces of attraction, leading to boiling.

  • Boiling Point: The temperature at which a liquid turns into gas is called its boiling point. For water, this is 373 K (100°C).

  • Latent Heat of Vaporization: The heat energy required to convert 1 kg of a liquid into a gas at its boiling point is called the latent heat of vaporization.

  • Observation: Particles in steam (water vapor) have more energy than in liquid water at the same temperature because they have absorbed latent heat of vaporization.

• Sublimation:

  • Activity 1.13 (Sublimation of Ammonium Chloride):

    • Heat crushed camphor or ammonium chloride and observe the process of sublimation.

    • Sublimation is when a substance directly changes from solid to gas without becoming liquid.

• Key Concepts:

  • Heat energy changes the state of matter: Solid → Liquid → Gas.

  • Sublimation: Direct change from solid to gas; Deposition: Direct change from gas to solid.

This section explains the effects of temperature on changing the state of matter, detailing processes such as melting, boiling, sublimation, and the concept of latent heat.

Note on Temperature Conversion:

• Kelvin (K) is the SI unit of temperature.

• Celsius (°C) and Kelvin (K) are related by the following conversions:

  • To convert from Celsius to Kelvin:
    $\text{K} = \text{°C} + 273$

  • To convert from Kelvin to Celsius:
    $\text{°C} = \text{K} - 273$

• Example:

  • 0°C = 273 K (rounded off).

  • 373 K = 100°C (Boiling point of water).

This rule helps in converting temperatures between the Celsius and Kelvin scales.

1.4.2 Effect of Change of Pressure

• Pressure and State of Matter: The difference in the states of matter arises due to the varying distances between the particles of each state. By applying pressure, the particles of gases, which are spread out, are pushed closer together.

• Effect of Pressure on Gases: When pressure is applied to a gas enclosed in a cylinder, the particles of the gas are forced closer together. This can lead to a change in the state of matter, such as:

  • Liquefaction: Reducing the temperature and increasing pressure can liquefy gases.

• Example - Dry Ice (Solid CO₂):

  • Solid carbon dioxide (CO₂) is stored under high pressure. When pressure is reduced, solid CO₂ changes directly into a gas, skipping the liquid phase. This is why solid CO₂ is referred to as dry ice.

• Conclusion: The state of a substance depends on pressure and temperature, which together determine whether the substance is in a solid, liquid, or gas state.

• Deposition: The reverse process where gas directly changes into a solid is called deposition.

This shows the significant role pressure plays in the interconversion of states of matter.

Atmospheric Pressure and Units of Pressure

• Atmosphere (atm): The unit atmosphere (atm) is used to measure the pressure exerted by a gas, particularly the pressure exerted by the Earth's atmosphere at sea level.

  • 1 atmosphere (atm) is equivalent to 1.01 × 10⁵ Pascal (Pa).

• Pressure in Pascal (Pa): The Pascal (Pa) is the SI unit of pressure, and it is defined as the force of 1 newton per square meter (N/m²).

• Normal Atmospheric Pressure: At sea level, the atmospheric pressure is approximately 1 atmosphere (atm) or 1.01 × 10⁵ Pa. This is often taken as the standard or normal atmospheric pressure.

In summary:

• 1 atm = 1.01 × 10⁵ Pa.

• Atmospheric pressure at sea level is 1 atmosphere (atm), also 1.01 × 10⁵ Pa.

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Evaporation

• Change of State Without Heating or Changing Pressure:

  • Not all changes of state require heating or changing pressure. There are examples from everyday life where a substance changes from a liquid to a vapor without reaching its boiling point.

  • Examples include:

    • Water evaporating when left uncovered.

    • Wet clothes drying up.

• What Happens During Evaporation?:

  • Particles in motion: Particles of matter are constantly in motion and never at rest. At any given temperature, the particles in a substance (solid, liquid, or gas) have varying amounts of kinetic energy.

  • Evaporation Process:

    • In liquids, some particles at the surface of the liquid have higher kinetic energy compared to others.

    • These higher-energy particles can overcome the forces of attraction between them and escape into the air, turning into vapour.

    • This process is known as evaporation.

• Characteristics of Evaporation:

  • Evaporation occurs at any temperature below the boiling point of the liquid, not just at the boiling point.

  • Surface particles with higher energy are responsible for evaporation.

  • Evaporation is a cooling process because the particles that escape leave behind those with lower energy, thus lowering the temperature of the remaining liquid.

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These notes provide a clear understanding of the process of evaporation, its everyday examples, and how it differs from boiling.

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Factors Affecting Evaporation

Activity 1.14

• Procedure:

  1. Take 5 mL of water in a test tube and place it near a window or under a fan.

  2. Record the room temperature.

  3. Observe and note the time or number of days taken for the evaporation process to occur.

  4. Repeat the above activity on a rainy day and record the observations.

• Key Observations:

  • Temperature, surface area, and wind velocity (speed) are crucial factors affecting the rate of evaporation.

Factors Influencing the Rate of Evaporation:

1. Surface Area:

   • Evaporation is a surface phenomenon. The greater the surface area of the liquid exposed to air, the faster the rate of evaporation.

   • Example: Clothes dry faster when spread out because they have a larger surface area exposed to the air.

2. Temperature:

   • With an increase in temperature, the kinetic energy of the particles increases, enabling more particles to escape into the vapor state.

   • Higher temperature results in a faster rate of evaporation.

3. Humidity:

   • Humidity refers to the amount of water vapor already present in the air.

   • Higher humidity means that the air is already saturated with water vapor, reducing the rate of evaporation.

   • Lower humidity allows more water to evaporate because the air can hold more water vapor at a given temperature.

4. Wind Speed:

   • When wind speed increases, the particles of water vapor are carried away by the wind.

   • This decreases the amount of water vapor around the liquid, allowing more particles to evaporate.

   • Example: Clothes dry faster on a windy day due to the wind carrying away the evaporated water.

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These factors help us understand the conditions under which evaporation occurs faster or slower, such as spreading clothes out to dry on a sunny, windy day or the slower evaporation on a humid, rainy day.

How Does Evaporation Cause Cooling?

Evaporation is not only a physical change of state but also a process that causes cooling. Here’s how:

Mechanism of Cooling by Evaporation:

• When a liquid evaporates from an open vessel, the particles of the liquid absorb energy from the surrounding environment to overcome the attractive forces between them.

• Energy Absorption: During evaporation, the liquid particles gain enough energy to break free from the surface of the liquid and become vapor. This energy is absorbed from the surrounding air or surface, leading to a decrease in temperature in the surroundings.

• Resulting Cooling: The absorption of heat energy causes the surroundings to become cooler. This is why evaporation results in cooling.

Examples of Cooling by Evaporation:

1. Acetone on the Skin:

   • When you pour acetone (nail polish remover) on your palm, the acetone absorbs energy from your skin and evaporates, making your palm feel cool.

2. Water Sprinkling on the Roof:

   • After a hot sunny day, people sprinkle water on the roof or open ground because water’s large latent heat of vaporization helps cool the hot surfaces. As the water evaporates, it absorbs a significant amount of heat from the surroundings, causing cooling.

3. Perspiration and Cooling in Summer:

   • During summer, we perspire more because our body uses evaporation to cool itself down.

   • As sweat (liquid) evaporates from the body, the latent heat of vaporization is absorbed from the body’s surface, leaving us feeling cooler.

   • Cotton Clothes: Wearing cotton clothes helps in this process because cotton is a good absorber of sweat, and it allows the sweat to evaporate easily, helping the body stay cool.

4. Water Droplets on a Cold Glass:

   • When you place ice-cold water in a tumbler, water droplets form on the outer surface of the glass. This happens because the water vapor in the air comes in contact with the cold surface, loses energy, and condenses into liquid form, forming the droplets. This process involves cooling the air around the glass.

Conclusion:

Evaporation causes cooling by absorbing heat energy from the surroundings. This cooling effect can be observed in various daily life situations, from sweating and wearing cotton clothes in summer to the formation of water droplets on a cold glass.

Notes on Plasma and Bose-Einstein Condensate (BEC)

1. Plasma:

   • Plasma is a state of matter consisting of super energetic and excited particles.

   • These particles are ionized gases (atoms or molecules that have lost or gained electrons, creating charged particles).

   • Examples:

     • Fluorescent tubes and neon sign bulbs contain plasma.

     • Inside these bulbs, gases like neon (in neon signs) and helium (in fluorescent tubes) are ionized when electrical energy flows through them, creating plasma.

     • Plasma glows with specific colors depending on the gas used.

   • Stars (including the Sun) are made up of plasma due to extremely high temperatures.

2. Bose-Einstein Condensate (BEC):

   • Origin: The concept was proposed by Indian physicist Satyendra Nath Bose in 1920, and Albert Einstein predicted it as a new state of matter.

   • BEC formation: It is created by cooling a gas of extremely low density (about one-hundred-thousandth the density of normal air) to super low temperatures.

   • Properties: When the gas is cooled to near absolute zero, the particles behave in a collective way, almost like a single entity, exhibiting quantum mechanical properties on a macroscopic scale.

   • Nobel Prize: In 2001, Eric A. Cornell, Wolfgang Ketterle, and Carl E. Wieman received the Nobel Prize in Physics for achieving Bose-Einstein condensation.

3. Additional Information:

• Plasma and BEC are considered as the fourth and fifth states of matter, respectively, beyond the common solid, liquid, and gas states.

Measurable Quantities and Their Units

Quantity	Unit	Symbol
Temperature	Kelvin	K
Length	Metre	m
Mass	Kilogram	kg
Weight	Newton	N
Volume	Cubic metre	m³
Density	Kilogram per cubic metre	kg/m³
Pressure	Pascal	Pa