2. A forged signature might be identified by:  1. The signature looking IDENTICAL (i.e. the original signature was traced) Real signature Forgery

3. A historical forged signature (today’s focus) might be identified by:  2. The ink used being invented after the original writer died  3. The paper used being made after the original writer died (e.g. paper that contains chlorine)

4. Chromatography is a technique for separating mixtures into their components in order to analyse, identify, purify, and/or quantify the mixture or components. Separate Analyse Identify Purify Quantify ComponentsMixture

5. Simplified Definition: Chromatography separates the components of a mixture by their distinctive attraction to the mobile phase and the stationary phase. Explanation: Compound is placed on stationary phase Mobile phase passes through the stationary phase Mobile phase solubilizes the components Mobile phase carries the individual components a certain distance through the stationary phase, depending on their attraction to both of the phases Definition of Chromatography

6. By the end of this lesson you will be able to EXPLAIN how PAPER CHROMATOGRAPHY can be used by journalists / historians to prove that Hitler’s diaries were forged

7. 1.7 describe experimental techniques for the separation of mixtures, including simple distillation, fractional distillation, filtration, crystallisation and paper chromatography 1.8 explain how information from chromatograms can be used to identify the composition of a mixture.

8. Uses for Chromatography Chromatography is used by scientists to: Analyse – examine a mixture, its components, and their relations to one another Identify – determine the identity of a mixture or components based on known components Purify – separate components in order to isolate one of interest for further study Quantify – determine the amount of the a mixture and/or the components present in the sample

9. Chromatography key words Solvent – a chemical such as water that dissolves another chemical Solute – a chemical that is dissolved Solution – a mixture of a solvent and solute Differential – showing a difference, distinctive Affinity – natural attraction or force between things Mobile Phase – gas or liquid that carries the component Stationary Phase – the part of the apparatus that does not move with the sample

10. The Rf factor is used to compare the components of various samples. The Rf values of suspect samples can be compared with known samples. Rf = distance from the base line to the spot distance from the base line to the solvent front Solvent front the point at which the water stopped moving up the paper Centre of spot the point at which a band or spot of colour is Base line the line where the original sample was placed If two substances have the same Rf value, they are likely (but not necessarily) the same compound. If they have different Rf values, they are definitely different compounds.

11. Illustration of Chromatography Components Affinity to Stationary Phase Affinity to Mobile Phase Blue ----------------Insoluble in Mobile Phase Black Red Yellow MixtureComponents Separation Stationary Phase Mobile Phase

12. Preparing the Chromatography Strips ① Collect one experiment tray per table ② In pairs draw a line 2 cm above the bottom edge of the strip with a pencil and ruler ③ Write 5 crosses approximately 1.5cm apart so that they are evenly spaced ④ Dip a capillary tube into one of the food dyes and put a small spot on the cross. Repeat this for the other food dye solutions.

13. Developing the Chromatograms ① Pour a little water in the beaker to 1 cm depth ② Place the strips in the beakers. Make sure the water solvent does not come above your start line. ③ You may use a paper clip to attach the top of the chromatogram to the glass ④ Let strips develop for around 15 minutes so that the mobile phase (solvent + dye) has moved over half way up the stationary phase (paper). ⑤ Remove the strips and use a hairdryer to carefully dry them (takes 1 minute).

14. Order these stages of paper chromatography A line is drawn in pencil on the stationary phase The ink from Hitler’s diary, ink available during the second world war and modern ink samples are placed on the pencil line on the chromatogram. A sample of ink is taken from Hitler’s diary Chromatography paper is collected. This is the stationary phase. A mobile phase that is a solvent such as water is added to the bottom of the stationary phase. The mobile phase travels up the stationary phase until it meets the ink samples. The different inks absorb onto the paper. Some chemicals in the ink samples form bonds with the solvent and so become dissolved. These travel in the mobile phase up the paper. Some chemicals in the dissolved ink form strong bonds (have a high AFFINTY) with the paper as they travel. These take a longer time to move up the paper. The solvent reaches the end of the paper. Retention factor (Rf) values are calculated by dividing the distance travelled by the solute (ink) by the distance moved by the solvent. A B C D E F G H I J K

15. A mobile phase that is a solvent such as water is added to the bottom of the stationary phase. Some chemicals in the dissolved ink form strong bonds (have a high AFFINTY) with the paper as they travel. These take a longer time to move up the paper. B C H I Chromatography paper is collected. This is the stationary phase. A line is drawn in pencil on the stationary phase The ink from Hitler’s diary, ink available during the second world war and modern ink samples are placed on the pencil line on the chromatogram. A sample of ink is taken from Hitler’s diary The mobile phase travels up the stationary phase until it meets the ink samples. The different inks absorb onto the paper. Some chemicals in the ink samples form bonds with the solvent and so become dissolved. These travel in the mobile phase up the paper. The solvent reaches the end of the paper. Retention factor (Rf) values are calculated by dividing the distance travelled by the solute (ink) by the distance moved by the solvent. A D E F G J K 1 2 3 5 4 6 8 7 9 10 11 Order these stages of paper chromatography

16. Exam question

20. Instructions  1. Start from the grade C question and work to a higher grade  2. Tick the keywords that you have used  3. Once you have finished swap your paper with your neighbour. EXPLAIN how PAPER CHROMATOGRAPHY can be used to prove that Hitler’s diaries were forged (8 marks) DESCRIBE in no more than 3 sentences HOW you would do this (2 marks) EXPLAIN how chromatography separates substances using 5 grade B keywords (3 marks) EXPLAIN in detail reasons for using different solvents in paper chromatography using 5 grade A keywordss (3 marks) stationary, mobile, phase, solute, solvent, diary, ink, pencil Affinity, chemical, bond, stronger, separate, stationary, mobile, phase, solute, solvent, travel, different, Rf value Chemical, bond, stationary, mobile, phase, solute, solvent, travel, different, strong, weak, mixture, Rf value

21. Instructions  1. Start from the grade C question and work to a higher grade  2. Tick the keywords that you have used  3. Once you have finished swap your paper with your neighbour. Write an EBI on a post it note then hand back for them to answer your EBI EXPLAIN how PAPER CHROMATOGRAPHY can be used to prove that Hitler’s diaries were forged (8 marks) DESCRIBE in no more than 3 sentences HOW you would do this (2 marks) EXPLAIN how chromatography separates substances using 5 grade B keywords (3 marks) EXPLAIN in detail reasons for using different solvents in paper chromatography using 5 grade A keywords (3 marks) 1.Collect ink from Hitler’s diary, modern ink and ink available during World War Two 2.Draw a line in pencil on a paper stationary phase 3.Add a solvent such as water to the bottom of the stationary phase 4.The solvent is the mobile phase 5.The ink is a solute 1.Ink contains a mixture of chemicals 2.The solvent dissolves the chemicals in the ink by forming bonds with them 3.The chemicals in the solvent travel different distances up the stationary phase 4.Some chemicals form strong bonds with the stationary phase (ORA) 5.Chemicals that form bonds with the stationary phase travel slower 6.Chemicals that travel slower have lower Rf values 1.Different solvents contain different chemicals 2.Different solvents form stronger bonds with the ink solute than others 3.Some ink chemicals have a stronger affinity for the stationary phase than the solvent 4.By using different solvents some solvents will have a greater affinity for the ink chemicals 5.Some solvents give better separation of ink chemicals than others 6.Some solvents make it easier to calculate Rf values than others

22. By the end of this lesson you will be able to EXPLAIN how PAPER CHROMATOGRAPHY can be used to prove that Hitler’s diaries were forged