Understanding Matter

• Matter is anything that occupies space and has mass, examples include air, rice, water, and chairs. Emotions are not matter

Classifying Matter

• Early Indian philosophers classified matter into five basic elements: air, earth, fire, sky, and water, known as Panch Tatva
• Based on physical state, matter is further classifiable as solids, liquids, and gases
• Based on chemical composition, matter is classified as pure substances (elements or compounds) and mixtures (homogeneous or heterogeneous)

Particle Nature of Matter

• Matter consists of particles.
• Salt dissolves in water, but the water level does not change because salt particles occupy the spaces between water particles
• A few crystals of potassium permanganate can color a large volume of water, this is because millions of tiny particles exist in each crystal
• Particles of matter are very small.

Characteristics of Matter

• The particles of matter have space between them
• The particles of matter are continuously moving
• The particles of matter attract each other

Particles have space between them

• Salt or sugar dissolves in water without increasing the water level, because the salt particles fit into the spaces between the water particles.

Particles are continuously moving

• Blue or red ink spreads evenly in water due to the movement of water and ink particles
• Diffusion is the intermixing of two or more different types of matter on their own

Particles attract each other

• An iron nail is harder to break than a rubber band or chalk because the particles in the iron nail are held together with greater force.

States of Matter

• Matter exists in three states: solid, liquid, and gas

Solid State

• Solids have definite volume and shape, examples are sugar rock table gold and iron
• In solids, particles are closely held in an orderly fashion with limited movement

Liquid State

• Liquids have a definite volume but no definite shape, and take the shape of their container, examples are water milk petrol oil mercury and alcohol
• In liquids, particles are close but can move around

Gaseous State

• Gases have neither a definite volume nor a definite shape, examples include hydrogen, oxygen, carbon dioxide, and air
• In gases, particles are far apart with easy and fast movement

Properties of Solids

• The space between the particles is minimum
• The force of attraction between the particles is maximum
• Particle movement is minimum
• Solids have definite shapes and fixed volume
• Solids are the least compressible
• Solids rate of diffusion is the least

Properties of Liquids

• Liquids have no definite shape but have fixed volume, and take the shape of the container
• The space between the particles is intermediate
• The force of attraction between the particles is intermediate
• The movement of the particles is intermediate
• They are less compressible
• Their rate of diffusion is more than solids

Properties of Gases

• Gases have no definite shape or fixed volume; they occupy the whole container space
• The space between the particles is maximum
• The force of attraction between the particles is minimum
• The movement of the particles is maximum
• Gases are most compressible
• Their rate of diffusion is more than solids and liquids

Change of State

• A solid changes into a liquid when heated, a liquid changes into a gas when heated
• A gas changes into a liquid when cooled, a liquid changes into a solid when cooled
• Ice becomes water when heated; water becomes steam when heated
• Steam becomes water when cooled; water becomes ice when cooled

Melting

• Melting, also known as fusion, occurs when a solid is heated and the particles vibrate faster, leading the solid to melt into a liquid at a certain temperature
• The temperature at which a solid melts is its melting point, ice's is 0°C or 273 K
• Latent heat of fusion is the heat energy needed to change 1kg of a solid into liquid at atmospheric pressure at its melting point

Boiling

• Boiling occurs when a liquid is heated, this causes particles move faster and change into gas (vapour) at a certain temperature
• Boiling is a bulk phenomenon where the bulk of the liquid changes into vapour
• The boiling point is when liquid starts boiling, such as water at 100°C or 373K (273 + 100)
• Latent heat of vaporisation is the heat needed to change 1kg of liquid into gas at atmospheric pressure at its boiling point

Sublimation

• Sublimation occurs when a substance changes directly from solid to gas or gas to solid
• Solid camphor or ammonium chloride becomes vapour when heated and changes back into solid when cooled

Sublimation examples

• Ammonium chloride
• Camphor
• Naphthalene
• Iodine crystals
• Dry ice (solid carbon dioxide)

Effect of pressure on gases

• Applying pressure on gases causes particles to come closer, turning the gas into liquid
• Gases are liquefied by applying pressure and reducing temperature
• Compressed solid carbon dioxide, known as dry ice, turns directly into gas when pressure is reduced

Interconversion of Matter

• The states of matter are inter convertible by changing temperature or pressure
• Solid becomes liquid by fusion, liquid becomes gas by vaporisation
• Gas becomes solid by deposition, solid becomes gas by sublimation
• Gas becomes liquid by condensation, liquid becomes solid by solidification

Evaporation

• Evaporation is the change of a liquid into vapour at any temperature below its boiling point and is a surface phenomenon
• Surface particles gain energy to overcome attraction forces and change to vapour state

Factors Affecting Evaporation

• The rate of evaporation depends on surface area, temperature, humidity, and wind speed
• Increase in surface are increases the evaporation rate
• Increase in temperature increases evaporation rate
• Increase in humidity decreases evaporation rate
• Increase in wind speed increases the evaporation rate

Evaporation Causes Cooling

• Evaporation occurs when a liquid evaporates, particles absorb heat from the surroundings, leading to a cooling effect of the surroundings
• People sprinkle water on roofs or open grounds, this is because water absorbs heat during evaporation and makes the surface cool
• During summer, sweating increases because sweat absorbs body heat during evaportation
• Cotton clothes keep us cool in summer because cotton absorbs sweat and absorbs heat from the body during evaporation