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

·         Saturated hydrocarbons are called ALKANES

·         Small chain ALKANES are used as fuels

3.       The reaction is called COMBUSTION REACTION

4.       The word equation for  this chemical reaction is :

fuel (E.G. PROPANE) + OXYGEN → WATER + CARBON DIOXIDE + ENERGY (heat, light, sound)

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

fuel (PROPANE) + OXYGEN → CARBON DIOXIDE + CARBON MONOXIDE + WATER + ENERGY (heat, light, sound)

6.       The problem with this reaction is that CARBON MONOXIDE is produced this gas is a POISONOUS/HARMFUL GAS to the human body (see objective 5.11)

7.       Where can you find incomplete combustion?

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

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

10.   Describe the two chemical tests for water

11.   Describe the chemical test for carbon dioxide gas

12.   Describe a physical test for water

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

3.2 and 3.3 I can recall the general formula and displayed formulae of alkanes

What is the general formula for alkanes?

Cn Hn+2 (n represents the number of carbon atoms)

Describe and explain the trend in boiling point.

As the chain gets longer/bigger (it has strong intermolecular forces) they have higher boiling points.

Because it is harder to separate the bonds.

METHANE

ETHANE

PROPANE

BUTANE

PENTANE

DIFFERENT DISPLAYED FORMULA OF PENTANE

5.13 I can describe catalytic cracking of long-chain hydrocarbons

2004_cracking_liquid_paraffin.mpg

1. Why should you take the end of the delivery tube out of water before you stop heating?
To prevent 'suck back' which can cause rapid change in volume and break the testube (explosion)
2. Name the catalyst for cracking paraffin.
Aluminium Oxide
3. What method is used to collect the gas? Describe the reason why/process.

Over water. The gas doesn't dissolve in water, therefore it is the most suitable way to collect the gas.

4.  What is the process to distill the crude oil?
Cracking
5. Catalysts are used in this experiment. What is the purpose of it?
To speed up the experiment
6.
7.
8.

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

a) When the crude oil under goes FRACTIONAL DISTILLATION there are too many LONG chain hydrocarbons (e.g. BITUMEN) produced and not enough SHORT chain hydrocarbons (e.g. REFINARY GAS).

b) To solve these problems the LONG chain hydrocarbons undergo a chemical reactions called CRACKING/THERMAL DECOMPOSITION.



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

Fight For Your Right To Clean Air

(highlight to view the answers)

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

glucose + oxygen -> carbon dioxide + water + ENERGY

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

NO (nitrogen oxide) and NO2 (nitrogen dioxide)

c.       What condition is necessary for this reaction to take place?

High temperature

d.      In what common object is this condition found?

Car

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

Because high temperature can break the strong triple covalent bonds

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

HNO3, it makes acid rain (this is when NO or NO2 reacts with water)

5.10 I can recall the problems associated with incomplete combustion

Carbon Monoxide Poisoning / Educational Video

Carbon Monoxide Poisoning

1.       What are the properties of carbon monoxide?

        Carbon monoxide is a poisonous gas which is colourless, odorless and tasteless

2.       Explain how carbon monoxide is formed.

        Carbon monoxide is formed when there is not enough oxygen available during the combustion process.

        This means that carbon monoxide is formed when the combustion is incompleted.

3.       Explain why carbon monoxide is poisonous

        Carbon monoxide is very poisonous because once you are exposed to it, carbon monoxide gets attached to your haemoglobin before oxygen does.  Therefore, it can cause serious problems.

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?

        The higher in the column, the lower the boiling point. This is because fractions which are located in higher place have small molecules (structure)

b.      Define viscosity (source your definition)

        Viscosity describes how well the liquid flows. E.g Water and ethanol have high viscosity. Honey has low (REMEMBER THE "SLOW") viscosity

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

        Viscosity of the fractions gets lower as it goes down the column

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

        The lower in the column, the darker

e.      Why is crude oil separated into fractions?

        Because each fractions have different boiling points

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

        Fractional distillation is used to seperate the crude oil into different fractions

g.       What physical property allows this process to work?

        Different boiling points for each fractions