Testing for ions

A body is found in the sea, but the forensic scientist is suspicious and thinks that the murder took place elsewhere and the person has been dumped in the sea. Other possibilities include being drowned in a bath or a local fresh water lake next to a copper mine.

Purpose of activity.

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The purpose of the activity is to find out where the person was first killed by doing tests on different types of water, which she could have died from. By doing this, we should be able to find ions in the person’s lung and in the different types of water to help us in our experiment

Planning.

The first thing to do is to test the water in the person’s lungs to see what ions we would get, then test the water from the place where she was found and a place where she could have got killed to see what ions we would get, after getting all of the results from the different waters we would have to match the ions we have got from the lungs with the different waters while matching up the different the waters the one that don’t match would get eliminated until we get a perfect match.

There were 3 different types of water’s we had to test for and they were –

* Seawater – Na+, K+, Ca2+, Cl-, So42-, Co32-

* Lake water – Ca2+, Cu-, Cl-

* Bath water – Na+, Co32-

Safety points.

There were a few safety points that we had to be careful with so that the experiment would go right and that no one would get hurt.

1. Making sure that we wore goggles when doing the experiments.

2. Working with reactive chemicals.

3. Making sure that we don’t get the chemicals onto us.

4. Making sure that when we were using the wire loop we had to clean it after every use just in case the chemical left on the wire would not react with other chemicals when used.

5. Making sure that you don’t burn your hands when testing the chemicals underneath the Bunsen burner.

6. Making sure that you don’t spill the chemicals onto the floor or on others.

7. Making sure that you tidy up the equipment so that no one can get hurt

Materials and method used.

Materials used.

The equipment that we used for the experiment were –

Wire loop

Bunsen burner

Glass tubes

Chemicals

Method.

We had to do 2 separate test for the specific types of chemicals we did 2 different test so that we can get better results.

Testing with solutions.

1. Pour approx 3cm depth of control solution into a test tube.

2. Add a few drops of specified solutions.

3. Make a note of any colour changes or precipitates formed.

4. If a gas is produced, bubble the gas through limewater.

Flame test.

1. Clean a wire loop in a roaring Bunsen flame.

2. Rinse the wire loop in hydrochloric acid.

3. Dip the wire loop into the test solution or substance.

4. Test the solution by placing the loop back in the roaring Bunsen flame.

5. Make a note of any colour change in the flame.

Results.

These are the results we got after each chemical we tested.

Tested

For

With

Results

Ions present

Lungs

Co32

Limewater

The carbonate turned a milky colour

The carbonate ions was present

Lungs

Cl-

Silver nitrate

The calcium turned a white precipitate colour

The calcium ions was present

Lungs

Na+

Flame

The sodium turned a bright yellow colour

The was sodium ions present

Lake

Cl-

Silver nitrate

The calcium turned a white precipitate colour

The calcium ions was present

Lake

Cu2

Flame

The copper turned a green colour

The copper ions was present

Lake

Na+

Flame

The sodium turned a bright yellow colour

The sodium ions was present

Bath

Na+

Flame

The sodium turned a bright yellow colour

The sodium ions was present

Bath

Cl-

Silver nitrate

The calcium turned a white precipitate colour

The calcium ions was present

Bath

Co32

Limewater

The carbonate turned a milky colour

The carbonate ions was present

Bath

Cu2

Flame

The copper turned a green colour

The copper ions was present

Sea

Cu2

Flame

The copper turned a green colour

The copper ions was present

Sea

Na+

Flame

The sodium turned a bright yellow colour

The sodium ions was present

Conclusion.

I think that the test was successful because we were able to confirm that the person died in the seawater. We found out the ions that was in the person’s lungs matched the seawater and not the other substances.

Evaluation.

I think that our tests was successful because we tested the different types of water to find out that in the end we was able to tell what was the woman’s cause of death.

Strength’s and Weaknesses.

Strength’s

Weaknesses

Some of the different types of water gave off a better colour than others, which made it easier to tell what we were looking for.

The wire loop was made of a type of metal, which was quite reactive, which made the tests we did a bit different.

Each type of water gave off a different colour, which we found easy to tell what types of ions were present in that water.

We didn’t repeat the test to be certain that we got the same results when we were testing for ions.

Human error’s

Equipment error’s

Once we tested a type of water we didn’t clean the wire loop properly and so we got different results when we tested another.

The wire loop gives off a faint colour which makes it harder to tell what colour will be.

We didn’t get enough water to test for the ions so that we would have got a better result.

The wire loop is quite reactive which interfered with our results.

Modifications.

There are a few modifications that would have made the experiment even more successful like –

* Using an un-reactive wire loop like a platinum loop, which is un-reactive at all, which would have given better results to the experiment.

* We could have done the experiment a couple of times, which would have also given us better results to the experiment.

Discussion of vocational Implications.

A forensic scientists would carry out the tests in the same way as we did in school but they would use more reliable equipment for the tests for example they would use a mass spectrometry which is used to get readings of a sample that is put into the machine. When a sample is put into the machine by a scientist the machine would do tests to find out what they would know what they would be looking for after the test is complete the machine would give out a reading on paper showing what ions where present in the sample.