Mariah Joseph
DATE / /24 Lab 7
TITLE: TEST A LEAF FOR STARCH
AIM: To test a leaf for starch
APPARATUS & MATERIALS:
Beaker Green leaf
Bunsen Water
Boiling Ethanol
Test tube holder Iodine
Forceps
DIAGRAM:
METHOD:
1. A leaf was dropped into a boiling water bath and left to sit for 30s.
2. The leaf was removed from the water bath and dropped into a tube of alcohol in the
water bath. The tube was left to sit until all chlorophyll had come out of the leaf.
3. The leaf was removed from the boiling tube and dipped into water to soften it.
4. The leaf was placed on a white tile and covered in iodine solution. Ablu-black colour
showed that starch was present.
RESULTS:Parts of the leaf turned blue-black,showing starch was present.
PRECAUTIONS:
1.
2.
LIMITATIONS:
1.
2.
DISCUSSION:
Starch is formed during photosynthesis from glucose.While some glucose is used for respiration,some is
converted into starch for storage.In this experiment,the leaf is placed into boiling water to stop any
chemical reactions and soften the leaf. This is done to make chlorophyll easier to be extracted in the
ethanol as well as it makes the leaf more penetrable for the iodine.The leaf is then put into alcohol to see
if chlorophyll was present. When chlorophyll is present,it causes the alcohol to change to a green colour.
REFLECTION:
CONCLUSION:
