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aqa gcse chemistry free > T2 bonding, structure and the properties of matter > Flashcards

T2 bonding, structure and the properties of matter Flashcards

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1
Q

what is ionic bonding

A

electrostatic attraction between positive and negative ions

relatively strong attraction

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2
Q

how are ionic compounds held together

A

in a giant lattice

regular structure that extends in all directions in a substance

electrostatic attraction between positive and negative ions holds the structure together

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3
Q

state properties of ionic substances

A

high melting and boiling points (strong electrostatic forces between oppositely charged ions)

don’t conduct electricity when solid (ions in fixed positions)

conduct when molten or dissolved in water - ions are free to move

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4
Q

give 5 examples of positive and negative ions

what is important when working out a formula of an ionic compound

A

P: Na+ Mg2+ Al3+ Ca2+ Rb+
N: Cl- Br- SO2-4 No-3 OH-

ionic compounds are electrically neutral

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5
Q

how are ionic compounds formed?

A

reaction of a metal with a non-metal

electron transfer occurs - metal gives away its outer shell electrons to non-metal

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6
Q

what is a covalent bond

A

shared pair of electrons between 2 atoms

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7
Q

describe the structure and properties of simple molecular covalent substances

A

don’t conduct electricity (no ions)
small molecules
weak intermolecular forces
low melting and boiling points

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8
Q

how do intermolecular forces change as the mass/size of the molecule increases

A

increase

causes melting/boiling points to increase as well (more energy needed to overcome these forces)

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9
Q

what are polymers? What are thermosoftening polymers?

A

very large molecules with atoms linked by covalent bonds

special type of polymers, melt/soften when heated, no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature, forces are overcome with heating - polymer melts

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10
Q

what are giant covalent substances

give examples

A

solids, atoms covalently bonded together in a giant lattice
high melting/boiling points - strong covalent bonds
mostly don’t conduct electricity
diamond, graphite, silicon dioxide

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11
Q

name the allotropes of carbon

A 
diamond
fullerenes
graphite
nanotubes
graphene
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12
Q

describe and explain diamond

A

four, strong covalent bonds for each carbon atom
very hard, strong bonds
very high melting point
doesn’t conduct

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13
Q

describe and explain graphite

A

three covalent bonds for each carbon atom
layers of hexagonal rings
high melting points
layers free to slide as weak intermolecular forces between layers,
soft, can be used as lubricant
conduct thermal and electricity due to one delocalised electron per each carbon atom

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14
Q

describe and explain fullerenes

A

hollow shaped molecules
based on hexagonal rings but may have 5/7 carbon rings
C60 has spherical shape, simple molecular structure (buckminsterfullerene)

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15
Q

describe and explain nanotubes

A

cylindrical fullerene with length to diameter ratio
high tensile strength (strong bonds)
conductivity (deloc electrons)

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16
Q

describe and explain graphene

A

single layer of graphite

17
Q

what is metallic bonding

A

forces of attraction between delocalised electrons and nuclei of metal ions

18
Q

describe properties of metals

A

high melting/boiling points (strong forces of attraction)

good conductors of heat and electricity (delocalised electrons)

malleable, soft (layers of atoms can slide over each other whilst maintaining the attraction forces)

19
Q

what are alloys

why are they harder than pure metals

A

mixtures of metal with other elements, usually metals

different sizes of atoms distorts the layers so they can’t slide over each other, making them harder than pure metals

20
Q

describe the properties of simple covalent structures

A

low boiling and melting points due to weak intermolecular forces between molecules

poor conductivity when solid as no ions to conduct

poor conductivity when molten as no ions

mostly gases and liquids

21
Q

describe the properties of ionic structures

A

high melting/boiling points due to giant lattice of ions with strong forces between oppositely charged ions

poor conductivity when solid as ions can’t move

good conductivity when molten as ions are free to move

crystalline solids

22
Q

describe the properties of giant covalent structures

A

high boiling/melting points due to many strong covalent bonds between atoms

poor conductivity when solid in diamond and sand as electrons can’t move
good in graphite as free delocalised electrons between layers can move

poor conductivity when molten

generally solids

23
Q

describe the properties of metallic structures

A

high melting/boiling points as strong electrostatic forces between positive ions and delocalised electrons

good conductivity when solid as delocalised electrons are free to move through the structure

good conductivity when molten

generally shiny metal solids

24
Q

what are the limitations of the simple model

A

shows particles as spheres

doesn’t take into account different sizes of particles

no forces are shown

spheres are shown as solid

25
Q

what does the amount of energy needed to change state from solid to liquid or liquid to gas depend on

A

strength of the forces between the particles of the substance

nature of the particles involved depends on the type of bonding and the structure of the substance

the stronger the forces between the particles, the higher the melting/boiling point of the substance

26
Q

a pure substance will melt or boil at…

A

a fixed temperature

a mixture will melt over a range of temperatures

27
Q

3 states of matter

A

solid, liquid and gas

28
Q

what is nanoscience

A

science that studies particles that are 1-100nm in size

29
Q

state the uses of nanoparticles

A 
medicine (drug delivery systems)
electronics 
deodorants
sun creams (better skin coverage and more effective protection against cell damage)
30
Q

what are fine and coarse particles

A 
fine particles (soot) 100-2500 nm diameter
coarse particles (dust) 2500-10^5 nm diameter
31
Q

why do nanoparticles have different properties to those for the same materials in bulk

A

high surface area to volume ratio

aqa gcse chemistry free (13 decks)

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