STARCH

Introduction: 

We will see in different types of food if they have starch or not. The aliments are potato, frankfurt and jam. But in the first part of the experiment we work with a leaf.

Material:

- Bunsen burner
- Tripod Stand
- Wire gauze
- 250 cm3 beaker
- Boiling tube
- Forceps
- Test tube Holder
- Leaf to be tested
- 90% ethanol
- Iodine/potassium iodine solution

Objectives: 

1. Identify the presence of starch in leaves.
2. Relate the presence of starch with photosynthesis.
3. Identify the presence of starch in some food.

Procedure: 

This experiment we divide in two parts: the leaf and the 3 aliments

First Part: Leaf

We start remove a green leaf from a plant that has been exposed to sunlight for few hours.

Half-fill a 250cm3 beaker with water. We heat the water until it boils and keep the water at boiling point. Then we use the forceps to place the leaf in the boiling water. Boil for 2 minutes. (Turn off the bunsen burner) Place boiled leaf in a boiling tube containing 90% ethanol and later place the boiling tube in hot water and boil for 10 minutes or until the leaf decolourizes. (It may be necessary to replace the ethanol). Gently we remove the leaf and wash with a fine trickle of cold tap water. We spread the leaf evenly on a white tile an finally we add a few drops of iodine/potassium iodine solution to the leaf and note what happens.

QUESTIONS

1. The fotosintesi

2. CO2 + H20 --> C6H12O6

3. The leaf lose the turgent condition

4. The chlorophyll disappear. It doesn't have colour.

5. Because the sugar isn't soluble with ethanol





Second Part: Aliments

Material:
- Jam
- Frankfurt
- Potato
- Knife
- 3 watch glass
- Iodine


Procedure:
We put the 3 aliments in differents watch glasses. Then we cut the frankfurt in two parts, cut a small piece of potato. With the dropper, put the iodine in each aliment. Finally we compare the result.

Observations:
The potato is more black than the others, this significate that the potato have more starch than frankfurt and jam.