Practicals Flashcards
Test for glucose
benedict’s solution
place in water bath for 5 minutes
the colour will change from blue to brick red. If it is green or yellow, smaller amounts of glucose are present
Test for starch
Add a few drops of iodine solution to sample
a blue black colour indicates the presence of starch
Test for protein
Add 2cm3 of water to sample and shake (only if its not liquid)
add biuret solution
colour change from blue to purple
Test for lipids
place in test tube
add ethanol and shake
add equal volume of water
a cloudy white colour indicates the presence of a lipid.
Germinating peas test
As the peas start to grow, they respire, releasing heat. The thermos flask is insulated, so heat is not transferred to the surroundings and we can measure the change in temperature, between dead and alive peas.
Hydrogen carbonate indicator and insects
the indicator is red, but turns yellow when the carbon dioxide concentration increases. The test tube with the insect in will turn yellow as the insect is respiring.
Investigating anaerobic respiration in yeast
The test tube is bubbled into limewater
the limewater turns cloudy due to the carbon dioxide produced in anaerobic respiration
Why does breathing rate increase during excercise
Breathing rate increases to produce more oxygen in respiration. This oxygen is carried to the muscles and used as energy for muscle contractions.
Energy of food experiment
burn food over Bunsen burner, with a test tube of water, and measure the temperature difference
Use the equation e=mcΔT to calculate the energy content
describe a method to show the nut contains fat
-emulsion test
-grind nut
-add water
-ethanol
-emulsion layer/white
describe an experiment that shows how the net gas exchange from a leaf varies with light intensity
-place all the leaves in test tubes
-with hydrogen carbonate indicator
-place one in dark and one in light
-in the light, the indicator turns purple
-in the dark it turns yellow
-same size leaf, same time, same temperature, volume, conc etc
