States of Matter (1a)

Unit 1, Principles of Chemistry: Part 1, a

Solid

• regular arrangement

• low kinetic energy

• vibrate in fixed positions

• strong forces of attraction

Liquid

• arranged close together

• more kinetic energy than solid particles

• move past each other

• weak forces of attraction

Gas

• arranged far apart

• a lot of kinetic energy

• move randomly in all directions

• very weak forces of attraction

Evaporation

• liquid turns into a gas

• occurs at any temperature

• faster, because it is a surface level process

Boiling

• liquid turns into a gas

• only at a certain temperature

• slower, because all the particles need to overcome forces of attraction

Diffusion

Spreading out of particles from high concentration to lower concentration until there is equal concentration throughout.

Diffusion: temperature effect

• Increases with increase in temperature

• Because when particles are heated, they gain kinetic energy and move around more

Bromine Experiment

• Lower jar: Bromine gas

• Top jar: air

• When lids are removed, bromine diffuses upwards

• Air also diffuses downwards until both jars are uniformly brown

• Hydrogen variant

  • place a lighted splint to check

  • Expected: sound from top jar because H is less dense

  • But equal sounds from both jars

Melting

• solid to liquid

• heat energy absorbed transformed to kinetic energy

• happens at a specific temperature or melting point (m.p.)

Freezing

• liquid to solid

• reverse of melting, happens at (m.p.)

• needs a significant decrease in temperature and loss of thermal energy

Sublimation

• solid to gas directly

• very few solids, eg: iodine, carbon dioxide

• reverse reaction: desublimation, deposition

Potassium Manganate (VII) Experiment

Description

• when crystals are dissolved, a purple solution is formed

• a small number of crystals produce a highly intense colour

Explanation

• water and potassium manganate (VII) particles move randomly and slide across each other

• therefore mix easily

• diffusion in liquids is slower than in gases because particles are closer and move more slowly

NH₃ + HCl Reaction

• particles diffuse along the tube

• white ring of NH₄Cl forms where they meet

• ring forms closer to HCl end

• because Ammonia particles are lighter and move faster

• so they travel further in the same amount of time, and further away from the NH₄ end

Dilution of Potassium Magnate (VII)

Description

• solution can be diluted several times

• colour fades but doesn’t disappear until after many dilutions

Explanation

• indicates that there a lot of particles in a small amount of potassium magnate (VII) and so the particles are very small

Solvent

• liquid in which a solute dissolves

• eg: water in salt water

Solute

• substance that dissolves in a solvent to become a solution

• eg: salt in salt water

Solution

• mixture formed when a solute is dissolved in a solvent

• eg: sea water

Saturated solution

• a solution with the max. conc. of solute dissolved in the solvent

• eg: sea water in the Dead Sea

Soluble

• describes a substance that will dissolve

• eg: salt is soluble in water

Insoluble

• describes a substance that will not dissolve

• eg: sand is insoluble in water

Solubility

measurement of how much of a substance will dissolve in a given volume of a liquid

Solubility of Solids

temperature increase = solubility increases

Solubility of Gases

• pressure increase = more soluble

• temperature increases = less soluble

Solubility Practical

• pour tap water into a beaker

• heat to a specific temperature

• add solute one spatula at a time, with constant stirring until no more dissolves and some remains undissolved in the mixture

• monitor temperature and keep it uniform throughout

• record mass of empty evaporating basin

• filter the mixture of of solution and undissolved crystals into the evaporating basin

• evaporate the filtrate until dry crystals are formed

• record the mass of the evaporating basin with the dry crystals