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Investigation into the Properties of Covalent Substances - Chemistry IAA


Firstly, let's identify what the independent and dependant variables are:

Independent Variable - Number of carbon atoms
Dependant Variable - Melting point of substance

Independent variable causes a change in Dependent Variable and it isn't possible that Dependent Variable could cause a change in Independent Variable. So, the number of carbon atoms causes a change in the melting point.

  • Graphite rods x2
  • Wires x4
  • Crocodile clips x2
  • 1 set of batteries 
The circuit required in this experiment
1) Set up a complete circuit as in the diagram.
4) Record whether the bulb lights up or not.
5) Repeat this for each substance.

Diagram showing graphite rods in
sample solution

6) Dissolve 2 spatulas of substance in distilled water.

9) Add 200ml of distilled water to a 250ml beaker.
13) Repeat two further times.

As you can't produce a very good graph, you can only produce a table and it should look something like this:

Pattern from the Table
From the table, it is clear than urea and glucose cannot conduct as a solid or as a solution. This is because covalent bonds haven't got any spare electrons to have a flow of charge. From heating salol up, the melting point of the substance is 41.5 degrees. This shows that covalent bonds are quite strong and require some energy to break them.

Use same circuit to stop mistakes from happening
Same graphite rods so there is always same conductivity

The method was made reliable by
Checking that the circuit works
By heating the substance very slowly
Recording temperature to 1 decimal place
Ignore anomalous date and repeat to compensate

Ultimately, urea, glucose and salol didn't conduct as a solid neither as a liquid. However, we found that the melting point of salol was 41.5 degrees. This shows that covalent bonds don't conduct electricity. This is because covalent substance (with exception to graphite) share electrons between atoms and therefore don't have free electrons. This makes the substances not have a flow of electrons therefore charge.

About Will Green


14 comments so far:

  1. Hi, my investigation was about the electrolysis of salt solution, do you know anything about it?, thanks.

  2. I didn't unfortunately do that experiment for my IAA but I remembered doing an electrolysis experiment which you place an cathode and anode in a solution?

  3. Oh, thanks anyway.

  4. Oh, thanks anywa, oh how can an element with delocalised electrons.

  5. conduct electricity.

  6. If the electrons are de localised, you can agree that the electrons can move as they have no specific location on the element? This means that they are free to move around the element's surface which is a flow of charge. This is why metals are great conductors as the atoms link in a way which free up electrons to move freely.

  7. Thanks, for explaning this to me, I just wanted to ask, why did you say "ou can agree", I just wanted to and thans for the help.

  8. oh sorry, I ment "you can agree". Thanks.

  9. Just a way of confirming with you so you I know you know what I'm talking about.

  10. Oh right. Thnaks.

  11. Oh, sorry, I ment thanks.

  12. I meant "meant"

  13. did you do one on cracking? chemistry iaa gcse??

  14. No sorry, if you go to the top of the page and type in 'chemistry iaa', you will see all the iaas i have to offer.