Unit 3.5 I can recall the reaction of methane and bromine to form bromomethane in the presence of UV light

·         Alkanes react with bromine in the presence of UV light

·         Explain why this condition is necessary because the UV light is required for the energy to break the bonds between carbon and hydrogen

3.       What is this type of reaction called A substitution reaction

4.       State and explain the observations The bromine and methane mixture goes from brown to a colour-less gas, because Bromine is brown whereas when reacted, the product (Bromomethane and Hydrogen Bromide) are colourless, therefore the resulting solution is colourless.

5.       Draw the displayed formula of the reaction between methane and bromine (upload a photo)

6.       Write out a balanced (with state symbols) the reaction between ethane and chlorine

C2H6 (g) + Cl2 (g) --> C2H5cl (g) + HCl (g)

7.       State and explain the observations in this chemical reaction

From a yellow gas to a colourless gas

3.4 I can recall the products of complete and incomplete combustion of alkenes

1.       Saturated hydrocarbons are called Alkanes

2.       Small chain Alkanes are used as fuels

3.       The reaction is called combustion

4.       The word equation for  this chemical reaction is :

fuel (Alkane) + Oxygen → Carbon Dioxide + Water + ENERGY (heat, light, sound)

5.       If there is insufficient oxygen then the word equation is:

fuel (Alkanes_) + Oxygen → Carbon Monoxide + Water + ENERGY (heat, light, sound)

6.       The problem with this reaction is that carbon monoxide is produced this gas is a threat to the human body (see objective 5.11)

7.       Where can you find incomplete combustion?

In car engines

8.       What is used to reduce the harmful products from incomplete combustion?

A catalytic converter

9.       During incomplete combustion a smoky flame is often seen, explain this observation

Extn: write a balanced equation (with state symbols) for the combustion of propane gas

The unburnt carbon from the incomplete combustion forms the black soot of the smoky flame

C3H8 (g) + 5O2 (g) --> 3CO2 (g) + 4H2O (l)

Unit 5.13 I can describe catalytic cracking of long-chain hydrocarbons

1. A catalyst is: a substance that changes the rate of the chemical reaction without undergoing any permanent chemical change in the process
2. Catalysts are used to speed up the chemical reaction of cracking
3. A high temperature is needed not only to break the bonds between the existing long-chain molecules but also to increase the speed of the reaction with the increased heat




1. Why is a broken pot used in the experiment?
So that the silica can act as a catalyst for the cracking experiment
2. What the purpose of the cracking experiment?
To break up the long chain molecules into more useful long chain molecules
3. 

Unit 5.12 I can recall the problems associated with the fractional distillation of crude oil

3. a) When crude oil undergoes fractional distillation there are too many long-chain molecules (eg. bitumen) produced and not enough short chain hydrocarbons (eg refinery gases) 
b) To solve these problems the long chain hydrocarbons undergo a chemical reaction called cracking
(page 145 of chem 4 you) 

5.11 I can recall how nitrogen oxides are formed in car engines

a.       Write the general equation for the combustion of a fuel

Oxygen + Fuel ---> Oxides + Energy + Water

b.      During combustion the nitrogen in air can react to form what gases?

NOx gases, ie. NO and NO2

c.       What condition is necessary for the formation of these gases?

Extremely high temperatures

d.      In what common object is this condition found?

Cars

e.      Why is this condition needed for nitrogen to react?

Because nitrogen is a diatomic molecule with 3 strong covalent bonds, meaning that it's structure is similar to that of the inert noble gases which means they need high levels of energy to break the bonds

f.        What are the dangers of the products from this reaction?

NOx gases can cause lung disease, asthma, heart disease, bronchitis and can shorten your life expectancy by 9 years

Unit 5.10: I can recall the problems associated with incomplete combustion

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1. Carbon monoxide is a colourless, odourless gas that is toxic to the human body
2. Carbon monoxide is formed through incomplete combustion, or the partial oxidation of carbon containing compound
3. Carbon monoxide is poisonous because it attaches itself to the haemoglobin

Unit 5.9 I can describe the trend in boiling point and viscosity of the main fractions

a.       What is the trend in boiling point of the fractions?

As you go down the fractionating column the chain molecules are longer resulting in higher boiling points

b.      Define viscosity (source your definition)

The ability of a liquid to flow www.geonet.org.nz/volcano/glossary.html

c.       What is the trend in viscosity of the fractions?

As you go down the fractionating column the viscosity of the liquid produced increases

d.      What is the trend in colour of the fractions?

As you go down the fractionating column the colour of the fractions get darker

e.      Why is crude oil separated into fractions?

So that it is able to be used

f.        What process is used to separate crude oil into fractions?

Fractional Distillation

g.       What physical property allows this process to work?

The different boiling points of the separate fractions

Fractional Distillation Unit 5.8