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Chemistry > Paper 3 > Flashcards

Paper 3 Flashcards

1
Q

Solid

A

Very close
Regular arrangement
Energy of particles low
Fixed volume+shape
Cannot flow, only vibrate in fixed position
Cannot be easily compressed (particles are very close together with no space to move into)

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2
Q

Liquid

A

Close
Randomly arranged
Slide past and move around eachother
Can flow and takes shape of their container
Greater energy than solid particles
Fixed volume, no fixed shape
Cannot be easily compressed (particles close together with no space to move into)

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3
Q

Gas

A

Far apart
Randomly arranged
Move quickly in all directions
Highest energy
No fixed shape+volume
Can flow, completely fills their container
Can be compressed (particles are far apart with space to move into)

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4
Q

Change of state

A

energy transferred to substance: particles gain energy, overcome forces of attraction between particles
energy transferred from substance to environment: particles lose energy, forces of attraction form between them

Some overcome during melting, remaining forces overcome during evaporating, although some weak forces still remain between particles in gas state

Gas to solid - deposition/desublimation
Solid to gas- sublimation

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5
Q

Difference between physical and chemical changes

A

Chemical- require chemical reaction + chemical difference from reactants to products( particles differently joined and arranged). Normally irreversible/not easily. New substances made. Colour change, precipitate, gas, door change, temperature change.
E.g combustion, methane burning in air=CO2+H2O

Physical- change - requires energy and involves change in state (arrangement, movement, distance) but no change to particles themselves. Easily reversed, no new substances made. Change of state. E.g ice melt to water

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6
Q

Chemical and physical properties

A

Physical properties- can be measured or observed without changing substance’s chemical composition. E.g density, hardness, colour, melting/boiling
Chemical- ability of a substance to undergo a specific chemical change and change into a different substance. E.g flammability, corrosion/oxidation

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7
Q

Limitations of particle model (theory used to explain physical properties of solids,liquids, gases, describes arrangement and movement of particles in substance)

A

Does not show space between particles, forces of attraction between particles, particle size.
Presents particles as solid, spherical, i elastic spheres

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8
Q

John Dalton theory

A

John dalton 1803-
Studied pressure of gases - Gases consists of tiny particles in constant motion
atoms of same element are identical, atoms of different elements are different, atoms cannot be created/destroyed/broken down into anything smaller, atoms rearrange during chemical reactions to make new substances

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9
Q

J.J Thomson 1897

A

Discovered electrons
Used a cathode-ray tube to conduct an experiment which showed that there are small particles inside atoms
Disproved Dalton that atoms cannot be broken down into anything smaller.
Plum pudding model
Spherical mass of positive charge with electrons scattered inside

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10
Q

Democritus

A

Greek philosopher Democritus 450 BC

All matter was made up of tiny,Indivisible,solid atoms

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11
Q

Ernest Rutherford

A

The Geiger-marsden experiment (1909-1911)
Aimed beams of positive charged alpha particles at thin gold foil sheet. Some passed, deflected, bounced back
Disproved plum pudding model (they should’ve all gone straight through according to it)

Nuclear model - atoms have tiny central positive charged nucleus with most of the mass, rest of atom is empty space, electrons orbit the nucleus

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12
Q

Niels Bohr

A

Using mathematical ideas, improved Rutherford’s model
Bohr’s model 1913
electrons orbit in electron shells/energy levels around nucleus

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13
Q

Why does the atomic model change over time

A

New discoveries and experiments made
Experiment results disprove old model
new model explains the new evidence

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14
Q

Structure of the atom

A

Positively charged nucleus which contains subatomic particles: positive protons and neutral neutrons
Surrounded by negatively charged electrons orbiting in electron shells
Nucleus contains most of the mass
The radius of the nucleus is much smaller than the radius of atom

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15
Q

Sizes and relative sizes of atom and molecule

A 
Atom= 1x10^-10 m
= 0.1nm 
Diameter/radius/bond length size 
———————————
Small molecule
1x10^-9 m
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16
Q

Protons, electrons and neutrons

A

Relative mass=
proton:1, neutron:1, electron:0.0005
Relative charge=
proton:+1, neutron:0, electron:-1

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17
Q

Define atomic number and mass number

A 
Atomic number (at bottom)=number of protons 
Mass number (at top): total number of protons and neutrons
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18
Q

Define ion and isotope

A

Isotopes- atoms of same element with same number of protons but different number of neutron
Ion- electrically charged particles (can be positive or negative) when atoms lose or gain electrons

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19
Q

Mixture, compound, element

A

Mixture=two or more different substances not chemically joined together
Element- only one type of atoms with same atomic number
Compound- two or more elements chemically joined together

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20
Q

Purity of a substance

A

Chemistry: Consists only of one element/compound

Everyday language: substance that has nothing added to it (natural state and unadulterated)

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21
Q

melting point- distinguish pure from impure substances

A

Pure- sharp specific melting point

Impure/mixtures - melt over a range of temperatures

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22
Q

What the relative formula mass (Mr) of a compound is

A

Relative formula mass= sun of relative atomic masses

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23
Q

Many useful materials are formulations of mixtures

A

A formulation = mixture that has been designed as a useful product where each chemical in it has a particular purpose
Mixed in carefully measured quantities to ensure product has required properties
E.g medicines, perfumes, paints

24
Q

Filtration process

A

Insoluble solid from a liquid
Beaker with mixture, beaker with funnel and filter paper
Pour mixture in filter funnel, liquid drips through (filtrate) but solid particles caught in filter paper (residue)

E.g sand from water

25
Q

Filter paper

A

Has tiny pores in it which are large enough to let simple molecules, smaller liquid molecules and dissolved ions through but not large enough for undissolved solid particles

26
Q

Crystallisation process

A

Solid crystals from solution
Solution placed in evaporating basin and heated with a Bunsen burner/electric heater. Solvent evaporates, solid crystals begin to form. When all water evaporated, leave the solid crystals to air-dry.
E.g copper surface crystals from solution

27
Q

To obtain large, regularly shaped crystals

A

Put solution in evaporating basin and warm it by placing it over boiling water bath.
Stop heating before all the solvent has evaporated
Wait for remaining solution to cool
Pour excess liquid away/filter
Drug crystals using warm oven/air-dry

28
Q

Simple distillation

A

Separate solvent from solution
Works cuz solute has higher boiling point than solvent.
Solution heated with Bunsen burner/electric heater, solvent vapour evaporates rising up, cools in condenser and condenses dripping into beaker.
E.g water from salt solution

29
Q

Fractional distillation

A

Separate different liquids from mixture of liquids
Works cuz different liquids have different boiling points
Mixture heated. Vapour rise through a column (which is hot at bottom, cold at top). Vapour condenses when reach part of column that is below temperature of their boiling point and flows out of column.

30
Q

Two ways of obtaining different liquids from the column

A
  • Collect different liquids from different parts of column.Lowest boiling point collected at the top of column. E.g crude oil distillation
  • heat mixture to increase temperatures in column. Liquid with lowest boiling point collected first
31
Q

Chromatography

A

Separate mixtures of soluble substances
Stationary phrase, Mobile phrase
different dissolved substances attracted to phrases in different proportions- causes them to move at different rates
More soluble/more attracted to mobile phrase= travels up more
Less soluble/more attracted to stationary phrase=travels up less

32
Q

Paper chromatography

A

separates different pigments in coloured soluble substance
Stationary phrase=paper
Mobile phase=solvent
Paper lowered into solvent and it spreads up paper
Analytical technique separating compounds by their relative speeds in a solvent as it spreads through paper

33
Q

Thin-layer chromatography

A

Separate non-volatile mixtures
Stationary phrase=thin layer of inert substance supported on flat interactive surface e.g glass/plastic/aluminium foil
Mobile phase= solvent e.g silica gel/cellulose/aluminium oxide
UV light to see transparent, done in short time

34
Q

Interpret chromatograms

A

Pure substances produce one spot on chromatogram

Impure substances produces two or more spots

35
Q

Rf values calculations

A

Rf= distance travelled by substance/distance travelled by solvent

36
Q

Gas chromatography

A

Mobile phrase= inert carrier gas e.g nitrogen/helium
Stationary phrase= thin layer of unreactive liquid/solid on a solid support(e.g silica beads), lining walls of long coiled column inside thermostatically controlled oven
Detector measures amount of each substance in a mixture as it leaves column
Different substances travel at different speeds through column and leave at different times (retention times)
GC machine plots graph of detector reading against retention time
Solubility dependent on how soluble a substance is in the gas
main info gathered from chromatogram: number of compounds in mixture (number of peaks), amount of each compound present (height of peak)

37
Q

Metals and non metals

A

Metals= elements that lose electrons to form positive ions
Shiny, good electrical/heat conductors, high dense, high melting point, malleable, forms basic oxides

Non-metal= elements that gain electrons to form negative ions
Dull, poor electrical conductor, low dense, low melting point, brittle, forms acidic oxides

38
Q

Position of an element in modern periodic table

A

Elements arranged in order of atomic number
Elements with similar chemical properties are in columns (groups)
Elements in same group have same amount of electrons in their outer shell

Group - number of outer shell electrons
Period- number of shells

39
Q

Ionic compounds

A

Ionic bonding
Regular, repeating arrangement
giant ionic lattice
Metal and non-metal(Cation and anion)
Strong electrostatic forces of attraction between oppositely charged ions
Many strong bonds
Melted/dissolved to free ions so they can move and curry current

40
Q

Simple molecules

A

Weak intermolecular forces between the molecules
Intermolecular forces increase with size of molecules so larger molecules have higher boiling+melting points
Strong covalent bonds between atoms

41
Q

Giant covalent structures

A

Many strong covalent bonds
Electrostatic attraction between a shared pair of electron
Giant covalent lattice

42
Q

Polymers

A

covalent
Very large molecules
Relatively strong Intermolecular forces between polymer molecules
Chain of atoms

43
Q

Metals

A

Metallic bonding
Giant metal lattice
Strong electrostatic force attraction between positive metal ions and sea of delocalised electrons(which are free to move through whole structure)
When force applied, Layers of metal ions can slide over each other while still being attracted to the sea of delocalised electrons

44
Q

Limitations of dot and cross diagrams, ball and stick models and two/three dimensional models

A

Chemical formula model- does not show charges, bonds, shape
Dot and cross diagram- shows how atoms bonded and electrons, does not show 3d arrangement
2d diagram- does not show 3d arrangement
3d diagram- no spaces between ions, charges

45
Q

How Mendeleev’s arrangement was refined into the modern periodic table

A

Order of increasing relative atomic mass across rows
All elements in column had similar chemical properties
Left gaps for elements not discovered yet
Swapped the order of a few pairs of elements

46
Q

Vast array of natural and synthetic organic compounds occur due to the

A

due to the ability of carbon to form families of similar compounds, chains and rings as each carbon atom can form 4 covalent bonds

47
Q

Diamond

A

Each carbon is covalently bonded to 4 other carbons
No free electrons
Very hard, high melting point, does not conduct electricity
Rigid tetrahedral structure held together by many strong covalent bonds - hardness
Oil rig drills, cutting tools, tipped glass cutters
Regular lattice arrangement

48
Q

Graphite

A

Each carbon is covalently bonded to 3 other carbons
Layers of hexagonal rings with weak forces between the layers
Layers can slide over eachother
Soft and slippery
One electron from each carbon atom is delocalised so electron can carry charge

49
Q

Fullerene

A

Fullerenes - Large molecules of carbon with hollow shapes. different forms/allotrope of carbon with structure based hexagonal rings of carbon atoms (although the rings could be 5 or 7 too)
Buckminsterfullerene C60-spheres of carbon atoms which are made of large molecules. Weak intermolecular forces exist between each buckyballs. Slippery. Lower melting points. Drug delivery. Lubricants. Catalysts.

Carbon nanotubes- layer of graphene rolled into a tube shape. High tensile strength so can be stretched without breaking. Strong. Conduct heat:electricity. High length to diameter ratios. Nanotechnology, electronics, specialised materials (e.g reinforce materials in tennis rackets)

50
Q

Allotrope

A

Two more different forms of the same element

E.g graphite and diamond are allotropes of carbon

51
Q

Graphene

A

single layer of graphite. Very strong. High melting point. Large regular arrangement of carbon atoms joined by covalent bonds. Delocalised electrons free to move through structure. Giant covalent structure.
Drug delivery, electric circuits, composites, solar cells

52
Q

Bulk properties

A

Individual atoms do not have the physical properties of the substances that contain them
Bulk properties= properties due to the influence of many atoms/ions/molecules acting together

53
Q

Nanoparticles

A

1-100nm

Few hundred atoms

54
Q

Nanoparticles properties and uses

A

Large surface area:volume ratio, catalysts
Small size, paints, cosmetics, transparent sunscreens, self-cleaning window panes
Conduct electricity, small electrical circuits for computers
Lubricant coatings, reduce friction, artificial joints and gears

55
Q

Risks of Nanoparticles

A

Possible to breathe in or pass into cells
Might catalyse reactions harmful
Toxic substances could bind to Nanoparticles as large S:V ratio
or pass into bloodstream and reach the brain
Risks unknown as Nanoparticles are new (still being created and tested)

Chemistry (4 decks)

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