Chromatography

Here are the results for my chromatography. The colours aren't really visible so I marked an "x" in the middle of the colour stain. For one of the chromatography slips the solvent front was marked when the it was removed from the water but for some reason the blue colour was above the solvent front O: So I shall only calculate the Rf value of the first slip although the other one has more obvious colours.



Since Rf values are calculated as such:


The Rf value for the first slip is 2.9/9.9= 0.292(to 3sf)


With the Rf values, we can match 2 substances to see if they are the same (:

Flame test

(Flame test done on 26.07.11)



My partner also took videos but I can't possibly upload all so here's a video of a really pretty flame~ The metal is lead if I'm not wrong :D You can see the flashes of white but yeah the flame was a little off so the results weren't as nice as some other we did D:)



The colours of the flames are:
Barium - pale green
Calcium - red-orange
Copper - blue-green
Lead - white-blue
Potassium - lilac
Sodium - bright yellow

Ms Tan also showed us some substances which did not change the colour of the flame. These probably are not metals. Also, I thought the remains of the "human bones" she had was carbon since according to what I remember from chemistry, the burnt ("chaota") substances from cooking was also carbon. However the rambio website mentioned that most carbon escaped as carbon dioxide so I did research (: Here is what I learnt:

Cremated remains are mostly dry calcium phosphates with some minor minerals, such as salts of sodium and potassium. Sulfur and most carbon are driven off as oxidized gases during the process, although a relatively small amount of carbon may remain as carbonate. (rambio says it's silicon though. Hmmm)

Here is also the explanation for flame colours:

Origin of Flame Colours
Flame colours are produced from the movement of the electrons in the metal ions present in the compounds. For example, a sodium ion in an unexcited state has the structure 2.8.1. When you heat it, the electrons gain energy and can jump into any of the empty orbitals at higher levels, depending on how much energy a particular electron happens to absorb from the flame. Because the electrons are now at a higher and more energetically unstable level, they tend to fall back down to where they were before - but not necessarily all in one go. An electron which had been excited from the 2nd level to an orbital in the 7th level, for example, might jump back to the 2nd level in one go. That would release a certain amount of energy which would be seen as light of a particular colour. However, it might jump back in two (or more) stages. For example, first to the 5th level and then back to the 2nd level.Each of these jumps involves a specific amount of energy being released as light energy, and each corresponds to a particular colour.
As a result of all these jumps, a spectrum of coloured lines will be produced. The colour you see will be a combination of all these individual colours. The exact sizes of the possible jumps in energy terms vary from one metal ion to another. That means that each different ion will have a different pattern of spectral lines, and so a different flame colour.

:D so cool I should have done something related to this for SIP. Though it might have been too confusing for my brain ><


:) okay that's it. I will also post the chromatography results later.

Fingerprints homework

I didn't bring a camera on that day! I even asked around but no one had a camera so there are no photos for the iodine activity and the microscopic view of the polymer cast of my fingerprint. WILL REMEMBER TO BRING MY CAMERA/HANDPHONE NEXT TIME BLEH D:

(Ridges and pores activity)

1. Where are the pores found? Are they regularly spaced?
The pores are found along the fingerprint ridges. They are quite regularly spaced.

2. Are the lines of your print equally spaced throughout?
Yes there are (sort of). The spaces are quite even but not exactly the same.

(Cyanoacrylate (Superglue) fuming method)

1. If the contrast of the white print against the black background is still too faint for a good detailed photograph to be captured, what could be done to enhance the fingerprint?
It is possible to treat it with fluorescent dye to make it glow under UV light.

(Iodine fuming method)

1. What are the possible substances that may be used to render the prints more permanent?
A solution of starch and water. This can make the fingerprint last for several weeks or months.

2. Why does the print disappear?
The print disappears because the iodine vapor can escape quickly (this is just a guess, can't find out actual reason)

(Powder dusting method)

1. What is magnetic powder dusting and how does it work?
Magnetic powder dusting is using powder to dust over the fingerprint so as to be able to see fingerprints. The powder is then lifted up using a sticky tape to preserve it. It works as the powder attaches to any greasy/oily substance in the fingerprint deposit.

O: This website has a lot about fingerprints and how it is used in forensics. It also has how different patterns of fingerprints are developed:

During early embryonic development (four to five weeks) there is swelling of (mesenchymal) tissue on areas of the sole, palm and digits. These areas are known as volar pads. The pads stop growing at about 10 weeks of development but the hand continues to grow. The volar pads are then absorbed back into the hand and as the pads shrink the skin folds to produce the ridges of fingerprints. The first ridges begin to appear at around 10 weeks.

Based on the pattern of pad absorption and timing, various combinations of fingerprint can occur:

If ridges appear when the volar pads are quite pronounced, the ridge pattern is a whorl.
If ridges appear when the volar pads are less pronounced, the ridge pattern is a loop.
If ridges appear when the volar pads are nearly absorbed, the ridge pattern is an arch.

... Does that mean that the patten shows the order in which your ridges form? Other than my thumbs, most of my fingerprints patterns are loops, meaning the ridges on my other fingers appeared first O: cool

Anyway, the next activity was a fingerprint database. We were supposed to submit the pattern of our thumbprint and then collate the data from 210 and 213 to plot a graph. I plotted 2 graphs, 1 of the number of people and one of the percentage of the people:



The graphs were similar to the ones Ms Tan plotted, seeing that the amount of people whose thumbprint patterns are arches < whorls < loops. The percentage was calculated to see the number in relevance to the population size, since the number of people in each class is different.

I'm not sure which "american data" I am supposed to, but the compared to this data:
Arches: 5%
Loops: 60-70%
Whorls: 25-35%
(taken from here)

the fingerprint patterns data we have shows a higher percentage of people with arches. This could be due to the fact that the data has a smaller sample size, thus higher inaccuracy.

Fingerprints

-can be found in porous and non-absorbent

Principles:

1. Fingerprint is an individual characteristic. (even twins have different fingerprints although they have similar DNA. The environment changes the fingerprint)

2. A fingerprint will remain unchanged.

3. Fingerprints have general ridge patterns.

CSI Lesson 1

The case of the rubbish tosser.

What did Slylock observe to help him identify the trash tosser?

He observed a fishbone, which means that the raccoon did the crime as the bull is herbivore does not eat meat (while the raccoon is an omnivore and eats both plants and animals).

The raccoon is the trash tosser.

------

Moonwalking bear

I didn't even know it was a bear O.O He blended in very well with the black team (so much so that I couldn't even identify him the second time) so this shows that I really have to sharpen my observation skills!

-----

Reflection of the Interactive Investigator activity:

Result:

Your score is: 8, Good work, improving your reasoning will make you perfect.

Wilson: "So tell me Marlow, what do you think about the Hughes case. We've got two suspects in custody, and both vehemently deny that they murdered the victim. Monica Fitzgerald, that redheaded woman, says she was at home reading a book on the night of the murder. Patrick Murray A.K.A "Pat the Rat", the electrician, says he was at the Black Raven bar on that night; but no one remembers seeing him there. Then we have motives: Miss Fitzgerald had been the victim's lover for months until she was replaced by a pretty blonde. In her mind, she was going to become Mrs. Hughes; but it is obvious that Mr. Hughes had no such plans. She's the one who wrote the letter, and judging by what she says in it, she was furious enough to kill Robert Hughes.
Now if we look at "Pat the Rat"'s criminal record, he's been convicted twice for break and enter, and theft. Both times he stole from houses where he had worked as an electrician. He's also been arrested for assault, and records show that he participated in many fights when he was in prison, which shows that he can become very violent. So, he could have followed his old pattern of stealing from the houses where he works; which is not very bright if you ask me.

So what do you think happened?"

Kinds of physical evidence:

- Hair

- Fibre

- Footprints

- Scratch mark

- Letter

- Fingerprint

- Blood stain

- Wound

- Paint