NAME: …………………………………………. CLASS: ……….. DATE: ……………..

PRAC No: …………. Name of partner: ………………………

TEST FOR SATURATION IN AN ORGANIC COMPOUND.

This is a group activity. You will work with a partner. You are supplied with two organic compounds: cyclohexene and cyclohexane each in a test tube, but you are not told which is which. Both are liquids. Your task is to use bromine to identify which is saturated and which is unsaturated, and in this way to identify the liquids.

Bromine is a brown liquid. If the bromine reacts the brown colour will disappear. So the decolouration of bromine is an indication that the bromine has reacted.

Bromine is a poisonous and rather dangerous liquid and is not available in the pure form. But bromine water (bromine dissolved in water) can be purchased from chemical suppliers. But we have a problem. The bromine water that we purchased last year is completely clear in colour because all the bromine that was once in it has gone out of solution. So your task is now more complicated. You are required to make up your own solution of bromine in water, based on your knowledge of halogens and halides and the solubility of substances.

ASSESSMENTYou will be assessed on your ability to work co-operatively in a group planning skill – ability to plan the required procedure observation and recording skill ability to interpret data ability to draw conclusions

AIMS1. To prepare a solution of bromine.2. To use it to test for saturation in the organic compounds.3. To identify an alkane and an alkene.

INSTRUCTIONS

1. Plan a method for making your own solution of bromine in water, based on your knowledge of halogens and halides. You have access to the usual laboratory chemicals.

2. Carry out this plan.3. Place a small quantity of this bromine water in each of two test tubes. Add chloroform and shake so as

to make a solution of bromine in chloroform. 4. Now add one of the unknown organic compounds to one of these test tubes and the other compound to

the other test tube. 5. Based on your observations, identify which of the compounds is saturated and which is unsaturated.6. Identify which compound is cyclohexane and which is cyclohexene.7. Write a report on your findings, stating clearly the procedures followed. This write up should include: Aim Method for preparing bromine water Reason for shaking bromine water with chloroform (or some other suitable solvent) Procedure followed Observations and explanation Conclusions drawn.

NAME …………………………………………….. CLASS …………………. DATE …………….

ASSESSMENT RUBRICS

Group work skill CRITERIA Competency level

Works individually only 1

Works in a group, but does not participate fully 2

Works effectively with others, but not with full confidence 3

Works effectively and systematically and maintains a calm and confident approach. Assists others and performs practical without needing instruction. Knows exactly what to do.

4

(4)Recording skill

CRITERIA

Planning skill Competency level

No evidence shown that learner is able to plan the steps required to each the conclusion. 1Some evidence shown, but help was required

2Effective planning was carried out but the write up of the plan does not show all steps logically or a single error or omission 3The plan is presented in a correct and logical manner with good communication and error free. 4

(4)CRITERIA

Write-up Competency level

Poor presentation, layout confusing. 1

Presentation adequate. Material either incomplete or not well organised. 2

Material clearly and systematically organised, but an error or omission. 3Excellent presentation. Material organised systematically and clearly, so as to ensure complete understanding. All equations correctly given. 4

(4)Interpretation of data and drawing conclusions CRITERIA Competency levelIs incorrect in the identification of the compounds 1Makes an error in the interpretation and identification 2Is fully correct in the identification of saturation and of the compounds 3

(3)Explanation ability CRITERIA Competency level

Inadequate explanation provided 1

Most observations explained, but with error or omission 2

All observations clearly explained including all relevant equations for each step of the procedure

3

(3)

Total marks: 18 Mark achieved: ……………

Sample results for this saturation test:

TEST FOR SATURATION IN AN ORGANIC COMPOUND

1. Preparing chlorine water: Add dil. HCl to ‘Jik’

2. Preparing bromine water: Add the chlorine water prepared in 1. to a KBr solution. The bromine water now has a brown colour.

3. Add some chloroform CHCl3 to the bromine solution and shake up. The bromine does not readily dissolve in the water, but dissolves readily in the chloroform to form a yellow-brown colour in the chloroform and leaving the top layer of water, clear.

4. Now add this solution to each of the given, un-identified, original organic liquids.

5. In the case of liquid A, the yellow-brown colour in the chloroform disappears rapidly, while in the case of B, very little decolouration (if anything at all) takes place. When heated gently, the yellow-brown colour of the chloroform in B starts to decolourise and, in time, may even become clear.