Chemistry

• Chemistry is the study of matter and the properties of the forms of matter
• Branches of chemistry include:

  • Organic chemistry: study of compounds of carbon and its components
  • Biochemistry: study of chemical reactions or processes in living things like respiration and photosynthesis
  • Geochemistry: study of chemical composition and reactions associated with the earth and other planets
  • Inorganic chemistry: study of compounds not containing carbon
• Matter is anything that occupies space and has mass
• Basic units of matter are atoms, ions, and molecules
• States of matter: solids, liquids, gases
• Characteristic properties of the three states of matter:

  • Solids have fixed shape and volume, cannot be compressed, particles are closely packed
  • Liquids have no fixed shape, have fixed volume, cannot be compressed, particles are slightly further apart than in solids
  • Gases have no fixed shape or volume, can be compressed, particles are much further apart from each other
• Changes in state are physical changes that occur when the particles of a substance absorb or lose energy
• Heating involves the addition of heat to a substance, causing it to change from solid to liquid and finally to gas
• Melting is the change of state from solid to liquid, like ice changing to water when heated
• Evaporation is the change of state from liquid to gas, like water changing to steam when heated
• Sublimation is the direct change of state from solid to gas or gas to solid without passing through the liquid state
• Examples of substances that can sublime: iodine, ammonium sulphate, ammonium chloride, carbon dioxide
• The heating curve shows changes in temperature with time for a substance being heated
• Cooling involves the removal of heat from a substance
• Freezing is the change of state from liquid to solid, like water changing to ice when cooled
• The cooling curve shows changes in temperature with time for a substance being cooled
• Example question:

  • Choose from the following terms to answer this question:
  • Sublimation, diffusion, matter, liquefaction, ion
  • Which term describes:

  (a) The physical material of the universe

  (b) A basic unit of matter

  (c) Carbon dioxide gas changing to dry ice

  (d) The spreading movement of particles

  (e) A gas changing to a liquid

  • Solution:

  (a) Matter

  (b) Ion

  (c) Sublimation

  (d) Diffusion

  (e) Liquefaction
• Matter is classified as solid, liquid, or gas. State two physical properties of each:

  • Solid
  • Liquid
  • Gas
• Physical changes:

  • No new substance is formed
  • Usually easily reversible
  • Usually no energy is given out or taken in
  • The mass of the substance remains the same

  Chemical changes:

  • A new substance is formed
  • Usually not easily reversible
  • Usually energy is given out or taken in
  • The mass of the new substance is different from that of the starting substance
• The kinetic theory of matter states that matter is made up of tiny particles which are in continuous random motion
• Experimental evidence of the kinetic theory of matter:

  • Brownian motion is the continuous random motion of particles, particularly of gases and liquids
  • Brownian motion was first observed by Robert Brown in 1827 while studying pollen grains under water
• Diffusion is the movement of particles from a region of high concentration to a region of low concentration
• Factors affecting the rate of diffusion:

  • Temperature
  • Concentration
  • Size of particles
• Diffusion in liquids:

  • Demonstration experiment with potassium permanganate (VII) and water
• Diffusion in gases:

  • Gases move randomly at a very high speed
  • Demonstration experiment with oxygen gas and nitrogen dioxide gas
• Various apparatus used in chemistry:

  • Stop watch
  • Laboratory thermometer
  • Beam balance
  • Measuring cylinder
  • Burette
  • Pipette
  • Flasks
  • Beakers
• Conical flask:

  • Its shape enables uniform heating of the liquid it contains
  • Used for heating liquids for longer periods
• Beakers:

  • Come in different sizes
  • Used on tripod stand and gauzes for heating liquids
  • Used for mixing liquids while using volumes too big for a test tube
• Test tube:

  • Used for heating and mixing liquids or solids
• Evaporating dish:

  • Used for drying substances or keeping them free from moisture
• Funnel:

  • Used in pouring liquids
  • Used to guide liquids and other substances into containers
• Spatula:

  • A flexible metal, plastic, or rubber utensil
  • Used to scoop, lift, spread, or mix substances
• Bunsen burner:

  • Most common tool for heating
  • Connected to the cylinder or gas tap and lighted
  • Used as a source of heat
• Flames produced by the Bunsen burner:

  • Zone A: blue flame, hottest part used for heating
  • Zone B: blue-green flame, contains unburnt hydrocarbons
  • Zone C: yellow flame, luminous, coats things with a black deposit due to carbon charring
• Separation techniques:

  • Methods used to obtain pure substances from mixtures
  • Mixture: consists of physically combined elements
  • Solution: mixture of solvent and solute
  • Filtration: separates insoluble solid from liquid using a filter
• Distillation:

  • Process of vaporizing a liquid and then condensing the vapor
  • Simple distillation: separates a pure liquid from a solution containing dissolved solids
  • Fractional distillation: separates miscible liquids with different boiling points
• Distillate:

  • Pure and condensed liquid obtained by distillation
• Industrial application of fractional distillation:

  • Separation of various components of crude oil
  • Used in the manufacture of spirits like whisky, rum, gin
  • Separation of liquid air into nitrogen and oxygen
• Example:

  • Separation of a mixture using fractional distillation
• Properties upon which the mixture (liquids) depends to allow separation:

  • Liquids must be miscible
  • Liquids must have different boiling points