IB Chemistry IA idea · Medicines and health
IB Chemistry IA idea: why does hand sanitiser feel cold?
The chill of a sanitiser is evaporation taking heat from your skin, and it depends on the mixture.
These ideas are starting points, not an IA to copy. Never copy an idea blindly: make the question, method and analysis your own, and check your plan with your teacher.
Example research question
How does the ethanol content of ethanol–water mixtures (40, 52, 64, 76, 88 and 100% v/v) affect the maximum temperature drop (°C) of a probe wrapped in filter paper wetted with a fixed volume of liquid?
Change the system, the range or the method so the question is yours. Check it against the research question checklist in our Chemistry IA guide.
Variables
- You change
- Ethanol percentage (v/v) in ethanol-water mixtures, 40 to 100 percent (6 or more values)
- You measure
- Maximum temperature drop (degrees C) of a probe wrapped in filter paper wet with a fixed volume of liquid
- You keep the same
- Volume of liquid applied
- Same paper and probe
- Room temperature and air flow
- Starting temperature of probe and liquid
Method
Wrap a temperature probe with filter paper, add a fixed small volume of each mixture and log the temperature until it returns to room temperature.
Data analysis
Plot the minimum temperature and the cooling rate against composition; relate to vapour pressure and heat of vaporisation; propagate probe uncertainty; compare with Raoult's law ideas.
How it works
You change Ethanol in mixture (% v/v) and measure Maximum temperature drop (°C) in Ethanol–water on a probe, keeping Volume of liquid, Filter paper, Room temperature the same. Expect a graph of Maximum temperature drop / °C against Ethanol in mixture / % v/v: More volatile liquid should cool more.
Make it yours
Replace ethanol with propan-2-ol or add glycerol (as in some gels).
Extended Essay angle
Model non-ideal ethanol-water mixtures using activity coefficients and vapour pressure data.
Safety
Take care with: heat and hot liquids, hazardous chemicals.
Ethanol is flammable; keep small volumes, away from flames.
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