Chapter 1: Matter in our surroundings

• Matter


  Material that makes up everything in the universe
• Physical Properties of matter -Occupy space

  • Have mass
  • Made up of tiny particles
• Panch Tatva


  Five basic elements (according to ancient Indian philosophers): air, earth, fire, sky, water
• Classification of matter


  Based on physical properties and chemical nature
• When salt/sugar is dissolved in water, the particles spread throughout the water
• Just a few crystals of potassium permanganate can color a large volume of water, suggesting particles are very small
• Particles of matter


  Very small, beyond our imagination
• There is space between particles of matter
• Particles of matter are continuously moving
• Particles of matter intermix on their own through diffusion, which happens faster with increased temperature
• Particles of matter attract each other with varying strengths of force
• The strength of the force of attraction between particles varies for different materials
• Solid state


  • Definite shape, distinct boundaries, fixed volume, negligible compressibility
• Liquid state


  • No fixed shape, fixed volume, flow and change shape easily
• Solids and liquids can diffuse into each other
• Liquids


  • Have no fixed shape but have a fixed volume
  • Take up the shape of the container
  • Flow and change shape
  • Are not rigid but can be called fluid
• Solids, liquids and gases can diffuse into liquids
• Rate of diffusion of liquids is higher than that of solids
• Gases


  • Highly compressible
  • Particles move about randomly at high speed
  • Particles hit each other and the walls of the container
  • Pressure exerted by gas is due to force exerted by gas particles per unit area on the walls
• Melting point


  Minimum temperature at which a solid melts to become a liquid at atmospheric pressure
• Latent heat of fusion

  Amount of heat energy required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point
• Boiling point


  Temperature at which a liquid starts boiling at atmospheric pressure
• Latent heat of vaporisation


  Amount of heat energy required to change 1 kg of a liquid into gas at atmospheric pressure at its boiling point
• Pressure and temperature determine the state of a substance - solid, liquid or gas
• Change of state directly from solid to gas without changing into liquid state is called sublimation
• Direct change of gas to solid is called deposition
• Pressure


  Unit is Pascal (Pa)
• Atmospheric pressure


  Pressure of air in atmosphere, 1 atmosphere = 1.01 × 105 Pa, normal atmospheric pressure at sea level
• Sublimation


  • Sublimation of camphor
• Solid carbon dioxide (CO2)

  Stored under high pressure, converts directly into gaseous state on decrease of pressure to 1 atmosphere without coming into liquid state, also known as dry ice
• Pressure and temperature determine the state of a substance, whether it will be solid, liquid or gas
• Sublimation


  Change of state directly from solid to gas without changing into liquid state
• Deposition


  Direct change of gas to solid without going through liquid state
• Evaporation is a surface phenomenon, particles from the surface gain enough energy to overcome the forces of attraction present in the liquid and change into the vapour state
• Factors affecting evaporation


  • Increase of surface area
  • Increase of temperature
  • Decrease in humidity
  • Increase in wind speed
• Evaporation causes cooling


  Particles of liquid absorb energy from the surrounding to regain the energy lost during evaporation, making the surroundings cold
• Latent heat of vaporisation is the heat energy required to change 1 kg of a liquid to gas at atmospheric pressure at its boiling point
• Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at its melting point
• Measurable quantities and their units

  • Temperature (kelvin, K)
  • Length (metre, m)
  • Mass (kilogram, kg)
  • Weight (newton, N)
  • Volume (cubic metre, m3)
  • Density (kilogram per cubic metre, kg m–3)
  • Pressure (pascal, Pa)