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Chemistry - Paper 2 > chemical change > Flashcards

chemical change Flashcards

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1
Q

why does increasing the surface area increase the rate of reaction

A
  • if one of the reactants is a solid, breaking it up increases the surface area to volume ratio
  • same volume of solid, articles will have more room, so more collisions
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2
Q

why does using a catalyst increase the rate of reaction

A
  • provides alternate reactive pathway with lower activation energy
  • increases rate of reaction
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3
Q

what is the equation for a rate of a reaction?

A

amount used/ formed / time

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4
Q

when the product is a gas:

A

measured in cm^3

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5
Q

when the product is a solid:

A

grams

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6
Q

time

A

seconds

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7
Q

what are the 3 ways of measuring the rate of a reaction?

A
  • precipitation and colour change
  • change is mass and gas given off
  • volume of gas given off
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8
Q

explain precipitation and colour change

A
  • solution is transparent and solution becomes opaque
  • reactants are coloured and products are colourless or vice versa
  • can’t plot a graph b its subjective
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9
Q

explain change in mass and gas given off

A
  • use a mass balance
  • quicker reading drops faster reaction bc as gas is given off the mass reduces
  • take measurements at regular intervals and plot a graph
  • most accurate but releases gas into room
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10
Q

explain volume of gas given off

A
  • use gas syringe
  • more given off the faster the reaction
  • take measurements at regular intervals and plot graph
  • if reaction is too vigorous, can blow plunger out of the end of the syringe
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11
Q

how do you work out the mean rate of a reaction?

A

y2 coordinate - y1 coordinate / difference in time

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12
Q

how do you work out the rate of a reaction?

A

draw a tangent and find the gradient of the tangent

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13
Q

explain a reversible reaction

A
  • react and concentrations fall, so forward slows down
  • more products made concentration rise, backward speeds up
  • equilibrium closed system no overall effect means reached balance and wont change
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14
Q

what 3 things effect equilibrium

A
  • temperature
  • pressure (gas)
  • concentration
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15
Q

what is le chatelier’s principle?

A

if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract the change

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16
Q

what are hydrocarbons

A

the simplest organic compounds

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17
Q

what are the simplest types of hydrocarbons you can get and what is their formula?

A
  • alkanes

- cn h2n+2

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18
Q

what pattern do the carbons go in?

A

1, 2, 3 ,4

19
Q

what pattern do the hydrogens go in?

A

4, 6, 8, 10

20
Q

what happens to the hydrocarbons the length of the chain?

A
  • short = less viscous
  • short = more volatile
  • short = more flammable
21
Q

what is the equation for complete combustion of hydrocarbons?

A

hydrogen + carbon = carbon dioxide + water

22
Q

what are hydrocarbons used for?

A

fuels because of the amount of energy released when they combust completely

23
Q

what are the chemical symbols of hydrocarbon, oxygen, water and carbon dioxide?

A
  • CH4
  • O2
  • H2O
  • CO2
24
Q

what is crude oil?

A
  • fossil fuel
  • dead plankton millions of years old buried in mud
  • high temp and pressure turns to crude oil which can be drilled up from rocks where its found
25
Q

how are hydrocarbons separated?

A
  • mixture of different hydrocarbons, most of which are alkanes
  • separated using fractional distillation
26
Q

how does fractional distillation work?

A
  • heated until gas
  • enter fractionating column with temp gradient
  • long hc - high bp, short hc - low bp
  • end up separating
27
Q

how is oil used in daily life?

A
  • fuel

- petrochemical industry

28
Q

what are alkenes?

A

more reactive starting material used to make polymers

29
Q

what is cracking?

A

thermal decomposition reaction

30
Q

what are the different methods of cracking?

A
  • heat long chain hydrocarbons to vaporise
  • vapour pass over hot powered aluminium catalyst
  • long chain split apart on surface of specks of catalyst (catalytic cracking)
  • or mix with steam then heat (steam cracking)
31
Q

give two examples of pure substances and define pure substances

A

pure milk and beeswax and when nothing has been added to it and it’s in its natural state and contains one compound or element.

32
Q

how do you test the purity of a sample?

A

by measuring its melting or boiling point and comparing it with that of pure substances found in a data book

33
Q

what will impurities do to your measurements?

A

lower mp and increase melting range of substance and increase bp and resluts in sample boining over a range of temperatures

34
Q

what are formulations?

A

usefulmixtures with a precise purposemade by following a formula. each component is measured and contributes to the properties of it so that it meets its required function

35
Q

what are paints formulations composed of?

A
  • pigment (colour)
  • solvent (dissolve other components and alter viscosity)
  • binder (holds the pigment in place)
  • additives (change other properties of the paint)
36
Q

how do you test for chlorine?

A

bleaches damp litmus paper white because it’s acidic

37
Q

how do you test for oxygen?

A

glowing splint inside test tube containing oxygen the oxgen will relight

38
Q

how do you test for carbon dioxide?

A

bubbling co2 through limewater turns it cloudy

39
Q

how do you test for hydrogen?

A

hold a burning splint open at a test tube of hydrogen and you’ll hear a squeaky pop

40
Q

what is chromatography?

A

method used to separate substances in a mixture

41
Q

what is the mobile phase?

A

the solvent - liquid or gas as the molecules can move

42
Q

what is the stationary phase?

A

the paper - molecules can’t move as it’s a solid

43
Q

how do you calculate Rf values?

A

distance travelled by substance / distance travelled by solvent

Chemistry - Paper 2 (1 decks)

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