Chem Option Topic: Forensic Chemistry Notes

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9.9 Forensic Chemistry (1-i) Outline precautions that may be necessary to ensure accuracy and prevent contamination of samples for analysis There are three main sources of contamination 1. Addition of extraneous material, during collect, handling and transport such as soil etc. Precautions for this include using sealed containers, clean sterile utensils 2. State of laboratory- the cleanliness of the lab, including quality of air, presence of dust and other contaminants 3. Careless analysis- not wearing protective clothing such as gloves and coat and result in the adding of sweat, dandruff etc. By wearing protective clothing, correct storage, cleaning of equipment and taking caution this can be avoided (1-ii) Distinguish between organic and inorganic compounds Organic compounds contain carbon and usually also contain hydrogen nitrogen and oxygen but exceptions include CO2, CO and carbides) whilst inorganic compound do not contain carbon (1-iii) Explain that there are different classes of carbon compounds including Class | General formula | Example | Test | Hydrocarbons | Alkane CnH2n+2 Alkene CnH2n Alkyene CnH2n-2 | Methane Ethene Elkyene | Discolours Br2- slow Discolours Br2- fast Discolours Br2- fast | Alkanols | ROH | Methanol | Dry the sample with CaCl2,add a small piece of sodium bubbles of H2 | Alkanoic Acid | RCOOH | Methanoic Acid | Reacts with NaCO3 to give off CO2 | (1-iv) Explain that the inorganic chemical properties of soils and other materials may be useful evidence The composition of soil differs from place to place, and the movement of in from a crime scene can help place a person there if have a sample on them such as on their shoes. The compounds found within a location are specific to that soil is rarely found elsewhere thereby scientist can test its contents, look at it microscopically to identify parts of it or

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