S1.1: Intro To The Particulate Nature Of Matter Flashcards
What is an element?
neutral substance that cannot be broken down into simpler substances - only contains atoms of the same type (same protons)
What is a compound?
pure substance formed when two or more chemical elements are chemically bonded together - has different properties from its components
What is a mixture?
elements and compounds are interspersed with each other but are not chemically combined, meaning the components retain the same characteristic properties as when they are in their pure form
What is a solid?
occupy a fixed space and a fixed volume, particles held closely together in a lattice
What is a liquid?
fixed volume that takes up the shape of its container, particles close together but moving with random motion
What is a gas?
completely fills its container, can be compressed, create a pressure due to collisions, widely spaced particles moving with rapid, random motion
Gas molecules -> two types of kinetic energy
Translational kinetic energy: zig-zag motion
Convertible kinetic energy: spinning motion
What is dynamic equilibrium?
When the rate of the forward reaction = the rate of the backward reaction
What is heat?
A measure of the total amount of energy in a given amount of substance
-> depends on the amount of substance present
-> measured in joules
What is temperature?
Measure of the hotness of a substance -> collective kinetic energy
-> independent of the amount of substance
-> measure of the average kinetic energy of the substance
Absolute temp -> measured in kelvin (K)
Kelvin vs celcius
0K/-273°-> absolute zero (temp when all motion stops)
273K/0° -> Melting point of water
373K/100° -> boiling point of water
Changes in K and °C are the same -> in chem mainly use K
Explain how solids -> liquids -> gas using the kinetic theory of matter
Solid: lattice, molecules vibrating in place
+ heat -> vibrations intensified -> particle sufficient energy to break lattice -> particle free
Liquid: still attractive forces between the particles
+ heat -> particles move faster (+KE) -> enough energy to overcome attracted forces -> escape as vapor
Gas
What are intermolecular and intramolecular forces?
Inter: one particles attracted to another
Intra: forces holding a molecule together
Boiling point facts (+ one humidity one)
Vapor pressure = external pressure -> boiling
-> Boiling point depends on pressure
100kPa -> 373K -> boiling water
Boiling:
Bubbles (dissolved air in water -> water vapor -> boiling)
Humidity at 100% -> humans die
-> cannot cool down via evaporation
What are all of the changes in state processes called?
Melting
Freezing
Vaporization
-> evaporation (surface level)
-> boiling (vapor pressure = external pressure, throughout liquid)
Condensation
Sublimation (S -> G)
Deposition (G -> S)
What is a pure substance?
An element or compound with a definite and constant composition
What are different methods of separation?
Note: method of separation depends on the nature of the substance
Solvation
Filtration
Evaporation
Distillation (+ fractional)
Chromatography (paper, thin-layer and gas-liquid)
What is a homogenous mixture?
All components in the same phase, with uniform composition and properties throughout
What is a heterogenous mixture?
Components in different phases, non-uniform composition, properties are not the same throughout
(Can often see separate components -> physical boundary)
Polarity of solvents
+ definition of dipole moment
Différent solvents -> different polarities
-> water is most polar
-> pentane is least polar
Dipole moment -> uneven distribution of charge thought the molecule
Nonpolar things dissolve in nonpolar solvents
Polar things dissolve in polar solvents
! Always keep in mind when choosing a solvent !
Methods of seperation: filtration
Used to separate solid, undissolved particles from a liquid
Can be carried out under gravity (atmospheric temp)
Finer particles -> reduced atmosphere
(Centrifugation can also be used)
Method:
Filter paper placed in filter funnel above another beaker
Mixture of insoluble solid + liquid -> poured into the filter
Filter paper only allows small liquid particles pass through
Solid particles too large to pass through filer -> stay behind
(Separating funnel -> usually heterogenous mixtures of liquids)
Methods of seperation: solvation/evaporation/crystallization
Used when one component of a solid mixture is soluble
-> mixture warmed with solvent -> filtered to remove insoluble particles -> solvent removed by evaporation
Dissolved solid from a solution when solid is more soluble in hot solvent than cold
Solution heated -> allows the solvent to evaporate and leaving saturated solution behind
-> test if saturated -> dip glass rod in solution -> crystals form after cooling -> saturated
Saturated solution -> cool slowly -> solids come out of solution as solubility decreases -> crystals
Crystal collected by filtering the solution
Washed with distilled water to removed impurities -> dried
Methods of seperation: recrystallization
when an impure solid can be dissolved in a suitable solvent but heating
Allowed to cool slowly so solids permeates out as crystal
Washed away lingering solvent
Dried
Used to purify impure solids:
Hot solvent used to dissolve both organic solid+impurities -> solution cools -> solid crystallizes -> leave behind impurities
Use minimum amount of solvent to dissolve the solid and avoid loss of product
Solid impurities remain -> hot filtration
Solution cooled + crystallized -> crystal recovered (filtration)
Faster using Buchner apparatus (filtration under reduced pressure)
Methods of separation: simple distillation
Used to separate a volatile liquid from dissolved components
-> separate liquid and soluble solid
-> separates pure liquid from mixture of liquids
Method:
Solution heated and pure water evaporates -> vapor which rises up the neck of flask -> vapor through condenser -> cools and condenses -> pure water -> collected in beaker
All water evaporated -> solid solute left
Methods of separation: fractional distillation
Used to separate 2+ liquids which form a homogenous mixture with one another
Solution heated to bp of substance with lowest bp
Most volatile -> rise and evaporate first -> condenser (cool and condense) -> liquid -> beaker
When temp reaches the bp of the highest bp substance -> stop heating
-> electric heater safer for flammable substances
What is an example for the use of fractional distillation?
the separation of the components in petroleum is achieved by fractional distillation on an industrial scale
fractional distillation of crude oil is not carried out in school laboratories due to the toxic nature of some of the components of the crude oil, but it can sometimes be simulated using a synthetic crude oil made specially for the demonstration
Methods of separation: paper chromatography
Used to separate substances that have different solubilities in a given solvent
Method:
Spot of mixture placed on paper (pencil line)
Solvent allowed to rise up the paper (pencil line above solvent)
Different components partition between the solvents and the paper by different amounts -> rise at different rates (capillary action)
Developer used for colorless components
Retardation factor -> Rf -> distance traveled by component/distance traveled by solvent from origin
