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Year 9 Sciences > Chemistry EOY thing > Flashcards

Chemistry EOY thing Flashcards

(72 cards)

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1
Q

What is crude oil?

A

Crude oil is a
mixture
of many different compounds. Most of the compounds are
hydrocarbons

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2
Q

How is crude oil made?

A

Crude oil is formed from the remains of dead plants and animals, particularly plankton.
These organic remains were covered by mud and sand, and buried in the earth.
Over millions of years, these organic remains were compressed under a lot of heat and pressure.
The heat and pressure chemically changed the organic remains into crude oil.

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3
Q

Examples of fossil fuels?

A

natural gas, coal, crude oil

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4
Q

How is Fractional distillation with crude oil carried out?

A

Crude oil is a mixture of hydrocarbons with different boiling points.
The first step is to heat the crude oil to a very high temperature so that all of the compounds are evaporated from liquid to gas.
The hot gaseous hydrocarbons then rise up the fractionating column (because hot gas rises).
As they rise, they cool down, because the top of the column is cooler than the bottom.
The hydrocarbons will condense when they become cooler than their boiling point, and the liquid hydrocarbons then collect in trays and drain out.
The longer chain hydrocarbons condense at the bottom of the fractionating column because they have high boiling points.
Meanwhile the shorter chain hydrocarbons condense at the top of the column because they have much lower boiling points.

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5
Q

Whatare the features of shorter chain alkenes?

A

Shorter chain alkanes have lower melting and boiling points, so are more flammable, and more volatile.

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6
Q

What is cracking?

A

Cracking is the process in which larger chain hydrocarbons are split into smaller, more useful hydrocarbons.

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7
Q

What type of reaction is cracking

A

thermal decomposition reaction

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8
Q

What is a thermal decomposition reaction?

A

something which uses heat to break something apart

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9
Q

what is the process of catalytic cracking?

A

First, some long chain alkanes are heated until they vaporise into a gas
Then they’re passed over a hot, powdered aluminium oxide catalyst
This breaks the long chain alkanes into a shorter chain alkane and an alkene

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10
Q

How is steam cracking different to catalytic cracking?

A

Steam cracking is different because there is no catalyst involved. Instead the vaporised long chain alkane is mixed with steam at very high temperatures.

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11
Q

Why does cracking always produce one alkane and alkene

A

When a long chain alkane is cracked, there aren’t enough hydrogen atoms to make two alkanes. Hence, cracking will always produce one alkane and one alkene.

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12
Q

what is the difference and similarity between an alkane and an alkene?

A

Alkenes are similar to alkanes. Alkenes are also hydrocarbons and also an example of a homologous series.
The difference is that alkenes have a double bond between two carbon atoms, whereas alkanes only have single bonds.
Another way to express the presence of the double bond between two carbon atoms is to say that alkenes are ‘unsaturated’.

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13
Q

What feature does the double bond in alkenes give?

A

makes alkenes more reactive than alkanes

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14
Q

how can we we distinguish between alkanes and alkenes?

A

The test to distinguish between alkanes and alkenes is the bromine water test.
Bromine water (just bromine dissolved in water) by itself is an orange colour. But when it’s mixed with alkenes, all of the bromine will react, and so the solution loses its orange colour, and turns colourless.
This doesn’t happen when bromine water is mixed with alkanes, because alkanes are not reactive enough to react with bromine water. So when mixed with an alkane, the solution will stay orange.

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15
Q

what is the bromine water test?

A

to distinguish between an alkane and an alkene

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16
Q

what is an isotope?

A

atoms of the same element with the same atomic number but a different number of neutrons

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17
Q

how do you calculate relative atomic mass with percentage abundance of isotopes?

A

(percentage of isotope A times mass of isotope A) plus (percentage of isotope B times mass of isotope B) over a hundred

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18
Q

what is a hydrocarbon

A

a compound containing hydrogen and carbon atoms ONLY

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19
Q

what does it mean when alkanes are saturated/

A

that there are as many hydrogen atoms as possible in each molecule.

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20
Q

what is the general formula for alkanes?

A

CnH2n+2

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21
Q

what is a fraction?

A

mixture of molecules of similar chain length and boiling points, which are collected at the same point

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22
Q

are longer or shorter hydrocarbons more viscous and why?

A

longer hydrocarbons are more viscous as they have longer chain lengths, so there are more intermolecular forces.

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23
Q

are longer or shorter hydrocarbons more volatile and why?

A

smaller hydrocarbon chain lengths are more volatile due to few intermolecular forces

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24
Q

what does cracking produce?

A

short chain alkanes and alkenes

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25
what are the most useful fractions from crude oil?
the ones containing shorter chain hydrocarbons since they ahve a low boiling point, more flowy and not viscous
26
when does complete combustion occur?
when there is adequate oxygen and it produces co2 and water
27
when does incomplete combustion occur
when there isnt enough oxygen and it produces CO or C and water
28
what makes alkenes more reactive?
the double bond as it is broken in the reaction
29
how do alkenes burn
with a smokier yellow flame
30
what is more reactive, alkene or alkane?
alkene
31
what is an addition reaction?
where one molecule combines with another molecule, forming one larger molecule and no other products
32
What is the word equation for the complete combustion of a hydrocarbon?
hydrocarbon + oxygen ➔ carbon dioxide + water
33
describe catalytic cracking
First, some long chain alkanes are heated until they vaporise into a gas Then they're passed over a hot, powdered aluminium oxide catalyst This breaks the long chain alkanes into a shorter chain alkane and an alkene
34
What name is given to the small molecules that combine together to form a polymer?
monomer
35
what metals make good catalysts?
transition metals
36
what is a homologous series
A homologous series is a group of organic compounds that have similar chemical properties, due to them having the same functional group.
37
An unidentified liquid could be either an alkene or an alkane. To test which one it is, the liquid is reacted with bromine water. The bromine water turns from orange to colourless. What type of hydrocarbon is the liquid
an alkene
38
how did rutherford develop the nuclear model
In Rutherford's experiments, alpha particles were fired at a thin sheet of gold foil. Most particles passed through, but some were deflected off course. This caused him to hypothesise that there was a dense region of positive charge at the centre of the atom that repelled the alpha particles. As a result he developed the nuclear model of the atom, in which there was a central positive nucleus, surrounded by negative electrons.
39
what is activation energy?
The minimum amount of energy required for a reaction to take place is called the activation energy.
40
how do you name polymers?
Take the alkene name Put brackets around it Add 'poly' to the front of the name, before the first bracket. So ethene would become poly(ethene), while chloroethene would become poly(chloroethene).
41
why does cracking always produce one alkane and alkene?
When a long chain alkane is cracked, there aren't enough hydrogen atoms to make two alkanes. Hence, cracking will always produce one alkane and one alkene. (Alkenes are hydrocarbons with a double bond between two carbon atoms).
42
what is a polymer?
A polymer is a large molecule that is made from multiple smaller monomers.
43
Alkenes join together by...?
addition polymerisation
44
what is required for addition polymerisation?
double bonds and an alkene
45
how do alkenes react with bromine water>
the solution changes from orange to colourless. All alkenes will react with bromine water in this way.
46
Alkenes can react with hydrogen, halogens or water. What type of reactions are these?
The reaction of alkenes with hydrogen, halogens or water are all addition reactions, as these molecules add to alkenes across their double bonds.
47
what is cracking
Cracking is the process used to separate crude oil fractions into simpler, more useful mixtures of hydrocarbon compounds such as alkenes.
48
what is a disadvantage of many polymers?
Many polymers are not biodegradable. This means microorganisms cannot break them down, so they are very difficult to dispose of and may last for many years in landfill sites.
49
what releases more energy alkanes or alkenes?
alkanes
50
what is more likely to undergo incomplete combustion, alkene or alkane and why?
alkenes as they are more reactive than alkanes so they use the available oxygen faster as incomplete combustion occurs when there is not sufficient oxygen
51
what are all the addition reactions of the alkenes?
halogenation, hydrogenation, hydration
52
what is a monomer?
small molecules that react together in repeating sequences to form a very large/long molecule
53
what is activation energy?
the minimum amount of energy required for particles to react
54
How do catalysts increase the rate of a reaction?
Catalysts increase the rate of a reaction by providing a different pathway for the reaction that has a lower activation energy.
55
physical ways to separate mixtures>
filtration, crystallisation, distillation, chromatography
56
what is an ion?
it is a charged atom(s)
57
what are isotopes?
atoms of the same element with different number of neutrons.
58
what are four main factors which affect the rate of chemical reactions?
temperature, surface area of solids, concentration of solutions/pressure of gases, and the presence of a catalyst.
59
what is collision theory
used to explain how reactant particles react together and why their rate of reaction can vary
60
why does raising the temperature increase the rate of a reaction?
partciles collide more often and particles collide with more energy
61
why does increasing the conentration of reactants in a solution increase the rate of reaction?
since there are more partciles of the reactant moving around in the same volume of solution, and the more crowded together they are, the more chance of collision, and an increased frequency of collisions results in a faster rate of reaction
62
what is a catalyst?
its a substance that changes the rate of a reaction without chemically changing itself
63
what are some advantages of catalysts/
it is cheaper to use a catalyst without having to pay for the extra energy needed without one, so they save moeny and help the environment and helps combat climate change and save money
64
what is an alkane?
saturated hydrocarbon
65
why do lighter fractions make better fuels?
as they iginte more easily and burn with cleaner flames
66
why is carbon monoxide dangerous?
as it is a toxic gas, colourless and odourless, and the red blood cells pick up this gas and carry it around your blood instead of oxygen
67
two ways to crack hydrocarbons
passed over a hot catalyst, or mixed with steam and heated to a very high temperature
68
ethene can react with steam with a catalyst of steam to make?
ethanol
69
what is the chemical formula for ethanol?
C2H5OH
70
why does increasing the surface area to volume ratio increase the rate of reaction?
it increases the collisions between particles
71
why do you think a fridge has low temperatures?
lowering temperatures will slow down the reactions that make food go off
72
Why are catalysts useful for producing chemicals in industry?
Catalysts are used in industry because they lower the activation energy required, thereby making reactions more efficient and cost effective.

Year 9 Sciences (4 decks)

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