Friday, May 27, 2011

3.5I can recall the reaction of methane and bromine

·         Alkanes react with bromine in the presence of UV
·         Explain why this condition is necessary
This condition is needed because the heat energy breaks the bonds
3.       What is this type of reaction called
Substitution reaction
4.       State and explain the observations
Changes color from brown to colorless
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( + Cl2(g) -->
7.       State and explain the observations in this chemical reaction

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 (Hydrocarbon) + Oxygen Carbon Dioxide +Water + ENERGY (heat, light, sound)
5.       If there is insufficient oxygen then the word equation is:
fuel (Hydrocarbon) +Oxygen Carbon monoxide + Water + ENERGY (heat, light, sound)
6.       The problem with this reaction is that Carbon monoxide is produced. This gas is a danger to the human body (see objective 5.11)
7.       Where can you find incomplete combustion?
          In cars
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
         It's because of the soot (unburned carbon)
Extension- Write a balanced equation for the combustion of propane gas
C3H8 (g) + 5O2 (g) --> 3CO2 (g) + 4H2O (l)
10. Describe the two chemical tests for water      
 anhydrous copper sulphate turns from white to blue
      

 cobalt 2 chloride paper turns from blue to pink



3.1 I can explain the terms homologous series, hydrocarbon, saturated, unsaturated, general formula and isomerism





Term
Definition
Example
Homologous series
 In chemistry, a homologous series is a series of organic compounds with a similar general formula.

 All the Alkanes.
Hydrocarbon
an organic compound containing only carbon and hydrogen.

 Methane
Saturated hydrocarbon
A hydrocarbon that has only single bonds between each carbon atom

 all the Alkanes
Unsaturated hydrocarbon
Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms

 all the Alkenes
General formula
 Mathematical formula to show the ratio of one element to another

 CnH2n+2
Isomerism
In chemistry, isomers are compounds with the same molecular formula but different structural formulas

 2, Methylbutane

Tuesday, May 17, 2011

5.13 I can describe catalytic cracking of long-chain hydrocarbons

Define Catalyst
A substance that increases the rate of a chemical reaction
Why is catalyst used?
To increase the rate of chemical reaction
Why are high temperatures needed?
1) To obtain the energy needed to separate the long chain hydrocarbon
2) To also increase the rate of chemical reaction

Questions 
What are the conditions needed for catalyst cracking?
High temperatures
What does cracking do?
It converts long chain alkanes into into short chain alkenes
Would you want to remove the heat from the experiment? why?
No, because the gas contracts






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

When crude oil undergoes fractional distillation, there are too many long chain hydrocarbons ( eg. refianary gas) produced and not enough short chain hydrocarbons (eg. petrol). To solve these problems the long chain hydrocarbons undergo a chemical reaction called cracking

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


a.       Write the general equation for the combustion of a fuel
Fuel + O2 -----> Energy + CO2 + H2O
b.      During combustion the nitrogen in air can react to form what gases?
NOx (nitrogen and oxygen)
c.       What condition is necessary for the formation of these gases?
A high temperature
d.      In what common object is this condition found?
In cars/ Vehicles
e.      Why is this condition needed for nitrogen to react?
 because Nitrogen has very strong triple covalent bonds
f.        What are the dangers of the products from this reaction?
It can shorten your life by up to 9 years, due to lung disease, skin irritation, and cancers