Structure 1.1 Introduction to the particulate nature of matter Flashcards
What is matter?
Any substance that has mass and volume. Composed of atoms/ions/molecules/etc.
What is an element?
pure substance made out of atoms with the same number of protons, and cannot be chemically broken into a simpler substance
What is a compound?
Pure substance composed of two or more atoms of different elements chemically bonded in a fixed ratio
What is a pure substance?
Form of matter with consistent chemical composition, fixed properties and cannot be separated into simpler substances by physical means
What is a mixture?
More than one element or compound in no fixed ratio, which is not chemically bonded and can be separated by physical methods into pure substances (mixed but not chemically combined). Can have variable properties depending on composition
Heterogenous mixture
Mixture that does not have a uniform composition and properties throughout (e.g. rocky road)
Homogeneous mixture
mixture with a uniform composition and properties (e.g. steel, air, any aqueous solution)
Physical change
reversible change in the physical properties of a substance in which no new substances are formed
Solute
solid/liquid/gas that dissolves in a liquid solvent to form a solution of solvated ions or molecules
Solvent
A usually liquid substance that is capable of dissolving a solute
Solution
Liquid mixture in which the solute is uniformly distributed within the solvent i.e. homogenous
Solvated
(of a solute) surrounded by the solvent’s molecules
Hydrated
ions solvated with water (surrounded by water molecules)
Anhydrous
Containing no water/opposite of hydrated
Identify the solvent, solution and solute with sodium chloride dissolving in water
Solvent: water
Solute: sodium chloride
Solution: aqeuous mixture of sodium and chloride ions solvated with water
Soluble
dissolves readily in a solvent, particularly water
Saturated solution
a solution where no more solute can dissolve at a particular temperature
Solubility (of a substance)
amount of solute needed to form a saturated (maxed out) solution
What is the solubility of a substance expressed as?
Often expressed as the mass that will dissolve into 100cm3 at a particular temperature
Miscible
when liquids mix together, they form one uniform layer of homogeneous mixture
Immiscible
when liquids mix together, they do not mix and instead form two separate layers
What are the separation techniques?
Filtration
Evaporation
Recrystallisation
Distillation
Paper chromatography
What is filtration?
physical separation process that separates solid matter and fluid by the use of a filter medium that permits only the fluid to pass through
What does filtration work on?
heterogeneous, insoluble solid + liquid
What is the difference in physical property that allows separation in filtration?
Solubility
What is Evaporation?
type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. This technique involves heating the solution, so that the liquid evaporates. This leaves the solid behind, separating the two substances
Mixture type for evaporation?
soluble solid and a liquid, homogenous
What is the difference in physical property that allows separation for evaporation?
Volatility
What is recrytillisation for?
Purify organic compounds
What type of solvent is needed for recrytillisation?
solvent that dissolves the desired product more readily at a high temperature than at a low temperature (making a hot solution) + allowing the product to crystallize on cooling
What are the steps of recrytillisation?
Shake sample with the solvent and warm to dissolve
Filter solution hot.
Throw away residue
Allow the solution to cool slowly.
(If not crystals appear, add a single crystal as a seed/stir vigorously. If not crystals appear, you’ve added too much solvent)
Filter the solution cold.
Keep the residue
Wash the residue with a small amount of cold solvent (has to be cold to remove the soluble impurities)
Dry the product on a watch glass, either at room temperature or in an oven
In recrytillisation, what is the result of shaking the sample with solvent + warming to dissolve?
Product and soluble impurities also dissolve into the solvent. Insoluble impurities don’t
In recrytillisation, what is the result of filtering the hot solution + throwing away residue?
Insoluble impurities are trapped on filter paper
In recrytillisation, what is the effect of allowing the solution to cool slowly?
Product becomes less soluble as it cools -> eventually become crystals.
Soluble impurities stay in solvent
In recrytillisation, what is the effect of filtering it cool after allowing it to cool?
Filtration lets the soluble impurities (in solvent) pass through.
Keep the desired product. It will be contaminated with a small amount of solvent
In recrytillisation, what is the effect of washing the reside (after cold filtration) with solvent?
rinses off contaminated solvent
In recrytillisation, what is the effect of leaving the product (final step) on a watch glass to dry?
Leaves no residue + give final product
What is distillation?
process during which a liquid is heated to boiling point in order to vaporise it. The liquid is then condensed back into a liquid, separated from impurities and other solutes.
What type of mixture is distillation for?
two or more miscible (able to mix properly) liquids
What difference in physical property is needed for distillation?
Boiling point (lower one leaves first)
What is paper chromatography?
technique used to separate soluble solids from each other, based on how far they travel up a stationary phase
What type of mixture is required for paper chromatography?
soluble solids
What are the differences in physical property that allow paper chromatography to occur?
Aolubility in mobile phase
Attraction to stationary phase
What is the mobile phase in paper chromatography?
Liquid/gas that the molecules can move in (i.e. solvent)
What is the stationary phase in paper chromatography?
solid that the molecules cannot move in (i.e. chromatography paper)
Why is water an exception to the density rule of solids and liquids?
Liquid water is denser than solid water
What are the features of a solid?
definite shape
lattice configuartion
definite volume
no ability to flow
limited compressibility
highest density (usually)
Strongest force of attraction between particles
Particles are close together and vibrate in fixed positions, but don’t move around
What are the features of a liquid?
Attractive forces between particles are weaker than in solids
Particles vibrate, rotate and move around
variable shape
fixed volume
ability to flow
limited compressibility
greater density than gases + less than solid (usually)
What are the traits of a gas?
Attractive forces between particles are negligible
Able to move around
Always spread out
Particles vibrate, rotate and move around faster than in a liquid
shape expands to fit containers
variable volume
diffuses easily
high compressibility
lowest density
What causes a solid -> liquid?
Heat causes the particles to vibrate enough to cause this
What is the density of a substance?
Mass per unit volume (g cm-3)
What is the formula for density?
mass / volume
What is kinetic energy?
energy a particle possesses due to its motion
What is the formula for kinetic energy?
(mass x velocity^2) / 2
What is the relationship between heat, particle movement and temperature?
increased heat = increased particle movement = increased temperature
What is temperature?
A measure of the average kinetic energy of the particles in a substance
What occurs to particles when temperature is increased?
Average kinetic energy of particles increases + a greater proportion of them will have sufficient energy to overcome the forces of attraction between particles and change states
What is melting?
Solid -> liquid
What is boiling?
liquid -> gas
What is evaporation?
particles @ liquid’s surface -> gas (below boiling point)
What is condensing?
gas -> liquid
What is freezing?
liquid -> solid
What is sublimation?
solid -> gas without melting
What is deposition?
gas -> solid without condensing
What is boiling point?
temperature liquid transitions to become gas. (more specific: the temperature at which liquid and gas exist in equillibrium)
What is melting point?
temperature solids transition to liquids (solids and gases exist in equillibrium at this point)
What is absolute zero?
The temperature at which particles stop moving (i.e. -273.15 degrees Celsius)
What is an endothermic process?
Energy is absorbed by particles from surroundings (i.e. solid -> liquid OR liquid -> gas / more condensed -> less condensed)
Why does temperature not increased during a transitional phase between states of matter, despite heat being added?
supplied heat is exclusively utilised to overcome the attractive forces between the water molecules in the liquid phase
What is the Celsius scale based on?
100 degree range between the melting and boiling point of pure water under standard conditions
What is Kelvin?
the standard SI unit for temperature with the same increment size as Celsius
What is the formula for temperature in K?
temperature (C) + 273.15
What is the change in temperature (K) equal to?
Change in temperature (C)