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9.2 Lifestyle chemistry: 4. The nature of a solvent
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Syllabus reference (October 2002 version) | ||
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4. The nature of a solvent plays an important role
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Students learn to: |
Students: |
Extract from Senior Science Stage 6 Syllabus (Amended October 2002). Board of Studies, NSW
[Edit: 29 Aug 08]
Prior learning: Stages 4-5 outcome 4.7 (content: 4.7.5, 4.7.6 c); outcome
4.8 (content 4.8.5).
identify water and alcohol as commonly used solvents
- Water and alcohol (ethanol) are commonly used solvents, particularly for use in products that are applied to the skin of or ingested by people.
identify cosmetics and external medications where water is the solvent
- Water is used as a solvent for facial cleaners, hair shampoo, conditioners, moisturisers, some creams (oil-in-water emulsions) and some emulsions like calamine lotion. Antiseptic solutions (e.g. Dettol) are dissolved in water before being used to bathe wounds.
identify cosmetics and external medications where alcohol is the solvent
- Alcohol is used as a solvent for astringents such as facial toner and aftershave, some antiseptics, perfumes, hair sprays and hair revitalisers and personal insect repellents. Iodine is dissolved in alcohol for use as a common antiseptic (see next syllabus point, below) called tincture of iodine. Alcohol is also used in spray on pain killers.
explain the relationship between the properties of solvents and their use in cosmetics and external medications
- Alcohol is a solvent that is used in preparing some cosmetics and external preparations because it has the capacity to dissolve some organic substances. It can do this because one end of the alcohol molecule is non-polar.
- Some products such as antiseptic solutions use alcohol as a solvent because of its ability to dissolve some components that will not dissolve in water.
- Tinctures are medicines that use alcohol to dissolve substances that are normally immiscible in water e.g. iodine tincture.
- Some cosmetics and external preparations use alcohol because it evaporates quickly when applied to the skin or hair. Hairspray is a good example.
perform an investigation to gather data comparing the rate at which capsules, tablets, enteric-coated tablets and slow release tablets dissolve
- Perform the investigation by carrying out a procedure like the one provided below. Recognise where and when modifications are needed in the procedure and, if you make modifications, analyse the effect of the adjustments in relation to the comparisons you need to make when you finish testing.
- After data has been collected, report your findings. You may be able to rank the tested materials in terms of their solubility.
A sample procedure: solubility of tablets and capsulesFor this activity, samples of the following types of commercial products need to be collected: | |
| Type 1: | simple hard white tablets (The type that are taken 4 hourly for example) |
| Type 2: | soluble white hard tablets |
| Type 3: | true capsules (These have a gelatin like mould on the outside. Not capsulets.) |
| Type 4: | slow release tablets (The 12 hour cold preparation type) |
| Type 5: | enteric-coated tablets (These have what looks like a plastic coating on them.) |
| Type 6: | slow release capsules (These have a gelatin like capsule with different coloured or size granules inside.) |
| Ensure that all preparations have approximately the same mass. Test each type three times. | |
The following table would be appropriate to record results from the procedure described. This should be done for each type of tablet.
| Solvent |
Solubility of materials: Type 1. hard white tablets | ||
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pH = < 7 |
pH =7 |
pH = > 7 | |
| 25 mL of water at room temperature e.g. 25oC |
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| 25 mL of water at body temperature e.g. 37oC |
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identify data sources, gather, process, analyse and present information from secondary sources to identify how subdermal implants release their medication
- In deciding the type of data necessary for this investigation, you need to consider the type of information about dermal patches and subdermal implants that must be gathered.
- Gather information from a range of resources such as popular
scientific journals, digital encyclopedias and sites on the Internet.
Attempt to include commercial Internet sites as well as reliable scientific
Internet sites. (Some sites are provided below)
Patches, Pumps and Timed Release: New Ways to Deliver Drugs
FDA Consumer magazine, USAContraception (hormonal)
includes brief discussion of dermal patches
and subdermal implants. Womens Health Channel, Massachusetts, USAHormonal implants: contraception for a new century
Darney PD, Department of
Obstetrics, Gynecology, and Reproductive Sciences, University of California,
San Francisco, USANorplant Implants
Indiadiets.com, India
- Process the information by assessing its accuracy. This is best achieved by comparing all the information collected and by checking the credentials of the organisations presenting the information.
- Analyse the information by identifying patterns and relationships in the explanations offered. Check for any relationships between contradictions and the sources of the information.
- When you present your information to identify how dermal patches and subdermal implants release their medication, select and use appropriate methods to acknowledge sources of information. This assists your audience to understand your analysis and provides opportunities for further consideration of the source information.
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