STARCH

Introduction:
In this experiment we will use a bunsen burner, tripod stand, wire gauze, 250 cm3 beaker, boiling tube, forceps, test tube holder, leaf to be tested, 90% ethanol and iodine or potassium iodine solution to see in different food if they have starch or not. We have the leaf after been exposed to sunlight and food that we eat many times.

Objectives:
- Identify the presence of starch in leaves.
- Relate the presence of starch with photosynthesis.
- Identify the presence of starch in some food.

Procedure:
- Remove a green leaf from a plant that has been exposed to sunlight for few hours.
- Half-fill a 250cm3 beaker with water. Heat the water until it boils. Keep the water at boiling point.
- 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.
- 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 remove the leaf and wash with a fine trickle of cold tap water.
- Spread the leaf evenly on a white tile.
-Add a few drops of iodine/potassium iodine solution to the leaf and note any observations.

Questions:
1- Which is the origin of the starch that you can see in the leaf?Answer: From the glucose that was synthesized the starch 2- Complete the reaction and write the name of this process:Answer: CO₂ + H₂Oà C₆ H₁₂ O₆ + O₂     
3- Explain the significance of boiling the leaf in water. 
Answer: Lose the turgent condition. 
4- Explain the significance of boiling the leaf in ethanol. 
Answer: To lose the color (chlorophyll dissapears) 
5- Explain the significance of rinsing the leaf in water
Answer: Beacuse the lugol is not soluble with ethanol. 


SECOND PART: 
Material:
- Frankfurt
- Jam
- Potato
- Three watch glass
- Knife
-Iodine

Objective: 
To detect the preseure of starch in different foods.


Procedure:
- Put each food in different watch glass.
- Open the frankfurt in the middle.
- Cut an small slice of potato.
- Put an small piece of jam.
- Use the dropper tu put iodine.
- Compare the potato with the rest.
Lugol stains starch (specially)











Observations:
We can see that in the photo the potato have a different colout of the rest, this is because the potato have a lot of starch.