Year 10 Term 2 Flashcards
What are the intermolecular forces like between smaller molecules
They are weaker so less energy is needed to break them
What are the intermolecular forces like between larger molecules
They are stronger and more energy is needed to break them
Fractions that have a low boiling point…
…evaporate easily. The earlier a fraction evaporates, the more volatile it is
What does volatile mean
How quickly it reacts with oxygen
What happens when fractions burn
They react with oxygen in the air, the more volatile it is the quicker it mixes with air
What’s viscosity
A resistance to flow
The longer the hydrocarbon, the more viscous it is
What does the colour of a faction depend on and what happens when the molecules get smaller
Depends on size of molecules it contains
As molecules get smaller, colour gets lighter
What’s cracking hydrocarbons
Breaking down larger hydrocarbons into smaller ones
What’s thermal cracking
Long hydrocarbon chains are vaporised
Placed under high temp and pressure
Long chains ‘cracked’ as thermal decomposition takes place
Large chains split into smaller, more useful ones
Problems with thermal cracking
Doesn’t have much control over what products are made
Getting to high temps is expensive
Cost ineffective
What’s catalytic cracking
Long hydrocarbon chain vaporised and passed over catalyst
Heated to high temp
Long chains cracked as thermal decomposition takes place
When is catalytic used and what does it produce
Used in industry splits mostly between 8 and 10 carbons in length
Chains of this length are used for petrol
What’s an alkene
Family of hydrocarbon compounds with general formula CnH2n
Used to make plastics and other chemicals
Contain a double carbon to carbon bond
Simplest alkene with formula
Ethene C2H4 H H | | C=C | | H H
Second simplest alkene with formula
Propene C3H6
H H H
| | |
H —C—C=C
| |
H HThird simplest alkene with formula
Butene C4H8
H H H H
| | | |
H —C—C—C=C
| | |
H H H
