chem pracs - help! (1 Viewer)

[lil kat]

if anyone has notes on the chem pracs..please help! all i can find on the net are the dot points. there are no decent notes for the chem pracs which are just as important!

 

[smegthehead]

do you mean that you've neglected to do pracs from a while ago? and you need a quick fix?

 

[kimmeh]

well really, youre making notes of your pracs in your summaries anyway. i agree with smegthehead, you should be keping record of your prac work anyway since they answer syllabus dot points. The people i know write their pracs up, rather than have them typed. Maybe you should borrow your friends prac books because some schools have different pracs.

 

[*girl04*]

lol i hate pracs! im scared of the chemicals! LIKE SERIOUSLY I AM , and the teacher is like oh my gosh ur doing chem 4 hgsc and u hate chemicals and im like yeah!

 

[smegthehead]

one of the guys in my chem class has not written up one single prac since the beggining of year 12, and we have done about 15 of them, he just seems to run out the room at the end of a period whenever he has his pracbook due for marking

 

[jimmik]

Originally posted by smegthehead
one of the guys in my chem class has not written up one single prac since the beggining of year 12, and we have done about 15 of them, he just seems to run out the room at the end of a period whenever he has his pracbook due for marking

i cant believe ppl like that get away wif things! our teachers start throwing detention slips at us if we even attempt to run away.

 

[CM_Tutor]

Originally posted by smegthehead
one of the guys in my chem class has not written up one single prac since the beggining of year 12, and we have done about 15 of them, he just seems to run out the room at the end of a period whenever he has his pracbook due for marking

This person has two problems coming.

Firstly, the teachers are required to certify to the Board of Studies that each and every member of the class has completed the requirements for practical work. So, when it comes time, the teaher will need to see all that lab work written up - or else they will have to certify without it, which is a no no. You can't get an HSC result in Chemistry without the certification.

Second, there are always questions that can't be answered unless you know the lab work, and there are traps that even being good at theory won't allow you to avoid. Consider, for example, the following question (q 16) from the 2002 HSC:

You have carried out a first-hand investigation to compare the reactivity of an alkene with its corresponding alkane.

(a) State the name of the alkene. (1 mark)

(b) Outline a procedure to compare the reactivity of this alkene with its corresponding alkane. (2 marks)

(c) Describe the results obtained from this first-hand investigation and include relevant chemical equations. (3 marks)

Now, suppose you haven't done the prac, and you try to answer it from theory. What will you put down? Well, the alkene that the syllabus goes on and on about is ethylene (ethene), so your answer would probably be:

(a) ethylene / ethene

(b) outline bromine water tests for ethene / ethane

(c) describe results, using relevant equations (esp. ethene + bromine ---> 1,2-dibromoethane)

How many marks can this get? Well, not many. No school would let its students do this with ethene - cyclohexene is the alkene of choice (cheap, liquid, easy to handle, and the toxicity of the alkane (cyclohexane) is way lower than the toxicity of hexane, which is why we avoid the straight chain forms). Ethene is a gas at RT, so the equipment setup is different, and also ethene isn't that esay to handle safely. So, (a) could be penalised. (b) says "this alkene", and the bromine water test outlined won't work the way it has been outlined, as the answer will be for testing a liquid alkene. (c) says "from this first-hand investigation", and again the description given will be for a liquid alkene.

In fact, the examiner's report on the 2002 paper makes this point. It says in the introductory comments that:

"The variation in the quality of responses seems to suggest that candidates who have actively planned and performed a first-hand investigation are more likely to have retained knowledge and understanding of the experience than those who have rote learnt an expected answer."

and again in the notes on q16:

"Most candidates answers indicated that they had carried out a first-hand investigation.

However, a significant number of candidates responded with reagents such as ethene, ethane, and chlorine which indicated that the candidate had not carried out a first hand investigation. The omission of equipment used or amounts of chemicals used also indicates a lack of first-hand experience. [My comment: or a lack of understanding of what is required for an "Outline a procedure" question.] The procedure was not done well by candidates who only had knowledge of the expected results."

In short, smegthehead, he'll get what's coming eventually, and keep doing the right thing.

 

[sikeveo]

oohh damn i better start writing them up

 

[CM_Tutor]

Sorry!