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chemistry-core > 1b > Flashcards

1b Flashcards

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1
Q

what does cracking mean

A

cracking means splitting up long chain hydrocarbons by passing vapour over a hot catalyst

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2
Q

if you were to crack a long chain molecule like diesel what 3 product would you get

A
  1. petrol
  2. parraffin
  3. ethene for plastics
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3
Q

cracking is a thermal decomposition reaction which breaks products down by…

A

heating them

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4
Q

describe the process of cracking

A

the first step is to heat the long chain hydrocarbon to vaporise it (turn it into a gas), then the vapour is passed over a catalyst at 400-700 degrees Celsius (aluminium oxide is the catalyst used), then the long chain molecules crack on the surface of the specks of catalyst

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5
Q

what bond does an alkene have

A

an alkene has a double bond

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6
Q

what are alkenes

A

alkenes are hydrocarbons which have a double bond between two of the carbon atoms in their chain

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7
Q

why are alkenes known as unsaturated

A

because they can make more bonds, the double bonds open up, allowing the two carbon atoms to bond with each other

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8
Q

what are the first two alkenes

A

ethene (with two carbon atoms)and propene (with 3 carbon atoms)

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9
Q

what is the general formula for alkenes

A

C(n)H(2n) (they have twice as many hydrogen atoms than carbon atoms

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10
Q

what is the formula for ethene

A

C2H4

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11
Q

what is tyeh formula for propene

A

C3H6

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12
Q

how can you test for an alkene

A

you can test for an alkene by adding the substance to bromine water, an alkene will decolourise the bromine water turning it from orange to colourless, this is because the double bond has opened up and formed bonds with the bromine

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13
Q

how is ethanol produced

A

ethene can be hydrated with steam in the presence of a catalyst to make ethanol

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14
Q

what is the process in which ethanol that makes beer and wine is produced

A

fermentation

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15
Q

what raw material is used for fermentation to make ethanol

A

sugar

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16
Q

what is the word equation for sugar being converted into ethanol using yeast

A

sugar = carbon dioxide + ethanol

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17
Q

what is polymerisation

A

this means joining together lots of small alkene molecules (monomers) to form very large molecules, these long chain molecules are called polymers

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18
Q

many ethene molecules can be joined up to produce…

A

poly(ethene)/polythene

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19
Q

what are the properties of poly(ethene) made at 200 d/c and 2000 atmospheres pressure

A

it is flexible, and has a low density

20
Q

what are the properties of poly(ethene) made at 60 d/c and a few atmospheres of pressure with a catalyst

A

it is rigid and dense

21
Q

why are most polymers not biodegradable

A

because they are not broken down by microorganisms, so they don’t rot

22
Q

how do you get any oil out of a plant

A

the plant material is crushed, then the plant material must be crushed between metal plates and the oil is squashed out, oil can also be separated from the crushed plant material by a centrifuge, or solvents can be used. Distillation is then used to refine the oil and get rid of any water solvents or impurities

23
Q

what fuel can be made from vegetable oil

A

biodiesel

24
Q

oils and fats contain __________ _________ molecules with lots of _________ atoms

A

oils and fats contain long chain molecules with lots of carbon atoms

25
Q

how many double bonds do monounsaturated fats contain

A

one double bond

26
Q

how many double bonds do polyunsaturated fats contain

A

more than one double bond

27
Q

unsaturated vegetable oils are ______ at room temperature

A

liquid

28
Q

explain how unsaturated oils can be hydrogenated

A

they can be hardened by reacting them with hydrogen in the presence of a nickel catalyst at about 60 d/c, this is called hydrogenation. The hydrogen reacts with the double bonded carbons and opens out the double bond

29
Q

vegetable oils tend to be _________ while animal fats tend to be _________ ( saturated/unsaturated)

A

vegetable oils tend to be unsaturated while animal fats tend to be saturated

30
Q

saturated fats are more/less healthy than unsaturated

A

less healthy, as saturated fats increase the amount of cholesterol in the blood, which can block up the arteries and increase chance of a heart attack)

31
Q

emulsions can be made from_______ and _______

A

oil and water

32
Q

what is an emulsion

A

oils don’t dissolve in water however you can mix oil with water to get an emulsion. Emulsions are made up of lots of droplets of one liquid suspended in another liquid, you can have an oil in water emulsion (oil droplets suspended in water) or a water in oil emulsion (water droplets suspended in oil)

33
Q

emulsions are ________ than both oil and water (thinner/thicker)

A

thicker

34
Q

what is an emulsifier

A

emulsifiers are molecules with one part that’s attracted to water and another that attracted to oil or fat. The bit that’s attracted to water is called hydrophilic, and the bit that’s attracted to oil is called hydrophobic

35
Q

the hydrophilic end of each emulsifier latches onto…

A

water molecules

36
Q

the hydrophobic end of each emulsifier latches onto…

A

oil molecules

37
Q

why does the emulsion between oil and water not separate

A

because when you shake oil and water together with a bit of emulsifier, the oil forms droplets, surrounded by a coating of hydrophilic bit facing outwards. Other oil droplets are repelled by the hydrophilic bit of the emulsifier, while water molecules latch on.

38
Q

what are the pros and cons of emulsifiers

A

pros
emulsifiers stop emulsions from separating out givng hem a longer shell life
they allow food companies to produce food that is lower in fat but also still has good texture
cons
some people are allergic to emulsifiers e.g. egg yolk

39
Q

what does wegener’s theory describe

A

continental drift

40
Q

what are the 4 layers of the earth

A

inner core, outer core, mantle and crust

41
Q

describe the properties of the crust

A

it is very thin and is surrounded by atmosphere

42
Q

describe the properties of the mantle

A

the mantle has all the properties of a solid, except that it can flow very slowly

43
Q

what takes place in the mantle

A

radioactive decay takes place in the mantle, this producesa lotof heat which causes the mantle to flow in convection currents

44
Q

what is the core made of

A

iron and nickel

45
Q

how are tectonic plates formed

A

when the crust and the upper part of the mantle cre cracked into a nuber of large pieces called tectonic plates.

46
Q

what causes tectonic plates to drift

A

convection currents

47
Q

how are earthquakes caused

A

they are caused by plates moving suddenly

chemistry-core (2 decks)

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