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# Water Of Crystallisation watch

1. What is the independent variable and the dependent variable in this experiment?
2. (Original post by Whatever210)
What is the independent variable and the dependent variable in this experiment?
Temperature? Decomposition? Environment(side reactions)?

What is this particular experiment anyway?
3. To find the number of moles, it's my ISA.
4. You're cheating, and you haven't even told us what the experiment this.
5. How is it cheating? It's your own common sense to look up the topic because you're told it before. The experiment is water of crystallisation - finding the number of moles.
6. Ok I know how to work out the number of moles but it'll ask to represent your data, so will it look like this?

Since the whole ISA will be done in one hour (as what my teacher told me) i dont think i can take more than one reading which doesnt really help the reliability of the data.

Also what hazards are there taking the experiment? And Safety Precautions?
7. An overview of the experiment would be helpful, we can't help you if we don't know what you're doing.

Aim - finding the number of moles in the water and determining the formula of a hydrated salt.

I know what to do, so the steps are:
1. Weigh the mass of the crucible & salt
2. Heat it until the salt is anhydrous
3. Weight it again
4. Calculate the mass lost
5. construct the formula

I want to ensure my table is appropriate for the exam for my ISA. I have doubts because it'll be better if I took atleast 2 readings but I don't think I'll have enough time.

I also just want to know if there are any hazards or safety precautions e.g. goggles for protection of eyes etc. A list would be really helpful.
9. Your table looks fine. If you get chance to do a second reading just add another column and take an average of the lost masses as your final mass loss value. The lack of repetition and it's effect on accuracy is something to mention in your discussion.

You should mention all usual lab safety bits - think about what you do and wear in the lab and why. Are there any toxic effects or dangerous properties in any of the chemicals you're using, and how will you reduce the risk of harm from them? What equipment will you be using and is any of it dangerous? Try going through the procedure in your head and thinking about what parts are dangerous.
10. ^ Thanks a lot for the help +rep

Just one more important question, the ISA is divided into three parts:
qualitative - my experiment
quantitative - ?

For the quantitative and evaluative, can any of the topics be picked that's stated in the OCR Practical Skills booklet? Please let me know, thanks.
11. Thanks for the rep

I should imagine anything on the syllabus or in your textbooks that is relevant can be used. In fact you may get a better mark for doing a bit of reading around.

Wouldn't quantitative be your experiment? Quantitative means something measurable, qualitative means an opinioned observation. Because you're measuring it, the number of moles of water in your sample is quantitative data.
12. I checked on the OCR Specification I have to do 2 experiments: one is water of crystallisation and the other is unkown then the evaluation task is an analysis. I've gone through all the tasks on the specification which can be tested. What else can I revise?
13. I didn't do OCR so I can't speak from experience, but I would imagine just go through the theory for practicals you've already done and common ones like titrations and enthalpy calculations.

Make sure you're clued up on things like molarity analysis and determining formulas, and on experimental procedures.
14. (Original post by Whatever210)
What is the independent variable and the dependent variable in this experiment?
Has anybody done it? How was it?
15. Has anyone done the water of crystallisation evaluative task? its seems like it will be difficult

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