1. 7. If the r.f. values are different, it means the inks are different
2. Finger Printing Reg 5, 14, 17, 20, 21
2.1. Types of finger prints
2.1.1. Visible prints
2.1.1.1. Visible prints are also called patent prints and are usually left in some medium that reveals them to the naked eye. They can be formed when substances on the finger come into contact with a smooth surface and leave an impression that is visible without development.
2.1.2. Impressed prints
2.1.2.1. Impressed prints are also called plastic prints and are actual indentations left in soft pliable surfaces, such as clay, wax, paint or other surface that will hold the impression. They are visible and can be viewed or photographed without development.
2.1.3. Latent prints
2.1.3.1. Latent prints usually refer to prints that are not apparent to the naked eye.
2.1.3.2. They are formed mainly from the sweat from sebaeceous glands (sweat pores) on the body or water, salt, amino acids and oils contained in sweat. The sweat pores occur in single rows along the ridges of the friction ridge skin.
2.1.3.3. The fluids create prints that must be developed before they can be seen or photographed. They can be made sufficiently visible by dusting, fuming or chemical reagents.
2.2. Finger print patterns
2.2.1. Loop
2.2.1.1. 60-65% of people
2.2.2. Whorl
2.2.2.1. 30 – 35% of people
2.2.3. Arch
2.2.3.1. 5% of people
2.3. Techniques of Extracting and Analyzing finger prints
2.3.1. Wood glue method
2.3.1.1. It captures ridge and pore details of your finger using a polymer cast.
2.3.2. Superglue fuming method
2.3.2.1. It develops latent prints on a non-porous surface using the superglue fuming method.
2.3.3. Iodine fuming method
2.3.3.1. It develops latent prints on a porous surface using the iodine fuming method.
2.3.4. Powder dusting method
2.3.4.1. It develops latent prints using the powder dusting method.
3. Chromatography Reg 28, 27, 26, 33, 7, 10
3.1. Uses of Chromatography
3.1.1. To separate different chemical components of a fluid
3.1.2. In forensic science: Identify forgery
3.1.3. Identify the chemical components of a fluid
3.2. Definition of chromatography
3.2.1. A method of separating and identifying components in a complex mixture by differential movement through a two-phase system
3.3. How to do chromatography
3.3.1. 1. Take a piece of chromatography paper. Draw a line a few cm from the bottom of the strip with a pencil
3.3.2. 2. Extract the ink from the sample
3.3.2.1. Take different portions of the allegedly forged document. Drop a small amount (around 1 drop) of water on the different ink samples to extract the ink from it.
3.3.3. 3. Place one drop of the extracted ink on the pencil line
3.3.4. 4. Insert the strip of paper into a suitable solvent that the ink can dissolve in (sometimes, water will just do) without letting the solvent level touch the line/drop of ink
3.3.5. 5. The ink would start moving upwards and separating into its different components as it goes. Wait until it has separated into its components clear enough for the distance traveled to be calculated easily.
3.3.6. 6. Calculate the r.f. value of the each component of every ink sample. The same ink should have the same/similar r.f. value for every component.
3.3.6.1. The retention factor value (aka the r.f. value) is calculated by the equation (distance moved by the component of the ink/distance moved by the solvent).
3.4. Experiences with Chromatography
3.4.1. Test different inks from a 'cheque'
3.4.1.1. 1.cut the written digits
3.4.1.2. 2. place them in separate (?) and add a drop of water. wait for the ink to dissolve
3.4.1.3. 3. Conduct chromatography with the different ink samples
3.5. R.f. values
3.5.1. Example: R.f. = 0.66 (for 60% ethanol)
3.5.2. R.f. values of a certain component remain constant so you can compare an r.f. value of an unknown substance to r.f. values of substances to identify it
3.6. New node
4. transition metals reg 03, 06, 08, 15, 19
4.1. elements/examples
4.1.1. barium
4.1.1.1. pale green to yellowy-green
4.1.2. potassium
4.1.2.1. lilac to red
4.1.3. sodium
4.1.3.1. intense yellow
4.1.4. calcium
4.1.4.1. orange to red
4.1.5. zinc
4.1.5.1. blueish green to whitish green
4.1.6. copper ll
4.1.6.1. green
4.1.7. lead
4.1.7.1. blue
4.2. definition
4.2.1. an element whose atom has an incomplete d subshell, or which can give rise to cations with incomplete d subshells - IUPAC definition
4.2.2. any element in the d block of the periodic table which includes group 3 to 12 [all elements in the d block are metals]
4.3. how to identify them?
4.3.1. FLAME TEST
4.3.1.1. different transition metals give off different colours when put in the flame
4.3.1.1.1. WHY?
4.3.1.2. procedure
4.3.1.2.1. step1: dip a clean flame test loop in the sample
4.3.1.2.2. step2: hold the flame test loop to the edge of a bunsen burner flame
4.3.1.2.3. step3: observe the changed colour of the flame and decide the transition metal it indicates
4.3.1.2.4. step4: clean the loop in hydrochloric acid and rinse with water
4.3.1.2.5. step5: repeat steps 1 to 4 with a new sample
4.3.1.2.6. REMEMBER: prevent cross-contamination of chemicals by first scooping a small amount on the dish
4.3.1.3. safety measures
4.3.1.3.1. take care when heating solids with a bunsen burner.
4.3.1.3.2. lithium chloride is an irritant.
4.3.1.3.3. hydrochloric acid is an irritant and will burn your skin.
4.3.1.3.4. barium chloride is harmful to swallow.
4.3.1.3.5. safety glasses must be worn.
4.3.1.3.6. long hair must be tied back.
4.3.1.3.7. treat all substances as potentially harmful and wash your hands thoroughly at the end of the experiment.
5. Blood Splatter Reg 1, 13, 18, 23, 29, 31
5.1. Equations for calculating
5.1.1. Vertical distance travelled by blood
5.1.1.1. s=ut+1/2at^2
5.1.1.1.1. s= vertical distance travelled by blood
5.1.1.1.2. u=initial speed of the blood
5.1.1.1.3. a=acceleration due to free fall (9.8m s^-2)
5.1.1.1.4. t=time take for the blood to reach the point of impact
5.1.2. Angle of impact
5.1.2.1. i=sin^-1 x W/L
5.1.2.1.1. W= width
5.1.2.1.2. L= length
5.2. Factors affecting shape and size of blood splatter
5.2.1. the higher the drop, the bigger the diameter of the circle formed by the blood droplet
5.2.2. the smaller the angle of the drop, the more elliptical the shape formed by the blood droplet
5.2.3. High velocity --> smaller blood splatters, spread out more Medium velocity --> larger blood splatters
5.2.4. When blood falls on a smooth surface, it is mostly circular in shape when blood falls onto a rough surface, it is not circular in shape (forgot the word)
6. Blood Identification Reg 4, 24, 25,16, 30, 32
6.1. Components of blood
6.1.1. Blood plasma
6.1.2. Platelets
6.1.3. Red blood cells
6.1.4. White blood cells
6.1.5. Hemoglobin
6.2. Definition of blood
6.2.1. Bodily fluid that delivers necessary substances to body cells. For example: oxygen, water, nutrients, minerals, etc.
6.3. Tests to identify blood
6.3.1. Kastle-Meyer Test
6.3.1.1. The iron in blood reacts with phenolphthalin to oxidise it and changes it to phenolphthalein, which in the presence of hydrogen peroxide, turns pink.
6.3.2. Luminol Test
6.3.2.1. Iron in blood acts as catalyst to decompose the hydrogen peroxide found in luminol to produce oxygen, which then reacts with the luminol to release energy which is seen as a bluish glow in the dark.
6.3.3. Hydrogen Peroxide Test
6.3.3.1. The enzyme, catalase, in blood reacts with the hydrogen peroxide and decomposes it, producing oxygen and water as byproducts, which is seen as foam.
6.3.3.2. Please note that cut potato will also test positive for this test
6.3.4. Limitations
6.3.4.1. These tests are presumptive tests. We cannot conclude directly and accurately based on only just 1 test but we can eliminate the other samples to obtain the final sample that is BLOOD. For example: the hydrogen peroxide test is a presumptive test, we would need to carry out other analyses to confirm the presence of blood.
6.3.5. Other tests such as the DNA test and Spectrophotometric test can be used to identify HUMAN blood
7. Instructions From Ms Siow
7.1. This Mindmap is private (editing rights), however, you can share this mindmap with anyone. You may wish to also share with your rgs.edu.sg account on mindmeister.
7.1.1. Do not share with others who will not contribute to the mindmap
7.2. In groups of 6, choose one of the following node to summarize on the topic. The others can read the Google Site on CSI, and only one laptop may be used to edit this mindmap
7.3. For groups who are faster, you may also make use of this lesson to update your e-journals
7.4. HOW TO USE
7.4.1. 1) Click + to add new sub-node. 2) Click on node and delete on keyboard to delete node. 3) You may also add in files such as images, add links, and add notes to this mindmap by clicking Properties at the right side
7.5. Feedback on USE OF MINDMEISTER Please add here.
7.5.1. (Do not DELETE, else... ) it is possible to track which group edited !!!!