Testing a leaf for starch

Question 1

Step 1 + Reason

Answer 1

Place leaf in boiling water

Kills leaf and stops all chemical reactions (denaturing enzymes)

Question 2

Step 2 + Reason

Answer 2

Boil leaf in ethanol (5 mins)

Removes chlorophyll from the leaf so we can see the colour change more easily

Question 3

Step 3 + Reason

Answer 3

Dip in boiling water

Washes off the ethanol and softens leaf so we can spread it out flat

Question 4

Step 4 + Reason

Answer 4

Add Iodide

To test for the presence of starch

yellow brown —> blue black

Question 5

Safety precautions when using ethanol

Answer 5

Ethanol is flammable, never use a flame to heat it. Boil it using a hot waterbath