Practical Flashcards
Why do scientists publish their results
Peer review
To inform scientists working on the same project
How do you test for reducing sugars
Add a few drops of benedicts solution
Then heat in a water bath
If brick red there is a positive test
If blue there are none
How do you test for proteins
Using biuret (or)
Add a few drops of copper sulfate to the solution
Then add a few drops of sodium hydroxide
A colour change to purple indicates a successful test
(Pale blue shows no proteins)
How do you test for non reducing sugars
Add a few drops of iodine to the solution
A positive test shows a colour change to blue / black
How do you test for lipids
Add a few drops of ethanol to the substance and shake it.
Allow it to stand for a minute and then add to water.
If the water turns cloudy lipids are present
How do you investigate the rate of transpiration
Using a potometer
An air buble is introduced to the capliary tube
As water is taken into shoots and evaporates the bubble moves towards the plant
Measure how fast the bubble moves to find out how fast the rate of transpiration is
You can then reset the bubble by adding water from the reservoir
You can also calculate the water lost by transpiration, by calculating the volume the bubble has used (volume of a cylinder where h is distance moved)
How can the results for food tests (e.g reducing sugars) be improved
Instead of looking by eye, use a colorimeter to identify the colour.
Also they could use a solution, where they know what is exactly in it
