Mystery food bench sim
Run the iodine, Benedict's, biuret and ethanol emulsion tests on an unknown food, heating the Benedict's tube in a water bath, record each colour in a results table and work out which food it was.
Biological molecules: food tests · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Four tests find four kinds of food molecule. Starch: add iodine solution; orange-brown turns blue-black if starch is there. Reducing sugar: add Benedict's solution and heat in a water bath at 80 °C or more (a boiling water bath is fine) for 3 minutes; blue turns green, yellow, orange or brick-red, the further along the more reducing sugar. Without heating it stays blue, so an unheated tube proves nothing. Sucrose (table sugar) is not a reducing sugar and stays blue. Protein: add biuret solution; blue turns purple (lilac). Fat: shake the food with ethanol, so any fat dissolves, then pour the ethanol into water; a milky-white emulsion shows fat, because the fat comes out of solution as tiny droplets. A negative result is no colour change: the tube stays the colour of the reagent. AQA's required practical tests fat with Sudan III (a red layer forms); this bench shows the ethanol emulsion test of O-Level and IGCSE. Each test uses a fresh tube of the food. Time moves only when you press Wait 1 minute. Model limits: the results are the textbook ones for each food, not measured (milk's Benedict's colour, for example, varies from orange to brick-red); a mystery food is shown as a plain pale sample, as a teacher would prepare unknowns to look alike; the Benedict's colour shows how much reducing sugar there is only roughly (it is not a measurement of concentration); the colours are drawn to match how the sources describe them.
- Test tubes 1–4: the food; tube 5: water for the emulsion test
- Water bath at 80 °C: Benedict's must be heated
- Reagents: iodine, Benedict's, biuret, ethanol
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
More biology sims
- Liver and hepatic portal vein simPlay a meal or a fast half an hour at a time, sample the hepatic portal vein and the hepatic vein, and see the liver store glucose as glycogen, release it again, and turn excess amino acids into urea.
- Molecule builder simDrag glucose units into starch, glycogen or cellulose, amino acids into a polypeptide, or glycerol and fatty acids into a fat, count the water each join releases, and split the bonds again by hydrolysis.
- Peristalsis simContract the circular muscles behind a bolus and the longitudinal muscles in front of it, segment by segment, then turn the oesophagus upright, lying down or upside down and switch gravity off: the food still arrives at the same speed.
- Smoking and the airways simSet how many cigarettes a day, watch tar stop the cilia and mucus build up in the airway, and measure how much haemoglobin carbon monoxide takes away from oxygen.
- Villus absorption simZoom from the gut wall into one villus and two of its cells, turn knobs for the microvilli, the wall's thickness and the blood flow, and run a minute at a time to see glucose and amino acids go into the blood and fats into the lacteal.
- Amylase: test the starch simMix the same volumes of starch and amylase in a controlled water bath.