Question 1
Aim: To test a leaf for starch. Materials: Safety goggles, water, two beakers, hot plate, leaf from a plant that has been left in sunlight for several hours, ethanol, boiling tube, pair of forceps, white tile, dropper, iodine solution.
1 Work in pairs. Put on your safety goggles.
2 Pour some water into a beaker. Stand the beaker on a hot plate and heat it till the water starts to boil.
3 Drop the leaf in the boiling water for one or two minutes.
4 Turn off the hot plate.
5 Pour ethanol into a boiling tube. Use as little as possible, just enough to cover the leaf. Use forceps to remove the leaf from the water, and carefully put it into the ethanol.
6 Stand the boiling tube in hot water. What do you observe about the ethanol? Explain what happens.
7 When the leaf is mostly white, gently remove the leaf from the boiling tube with the forceps. Wash the leaf with warm water to soften it.
8 Spread the leaf out onto a white tile. Use a dropper to add some iodine solution onto the leaf. Observe what happens.
Caution: Put on your safety goggles when heating substances. Ethanol is a flammable liquid. Use the smallest volume possible and keep it away from naked flames.
1 Work in pairs. Put on your safety goggles.
2 Pour some water into a beaker. Stand the beaker on a hot plate and heat it till the water starts to boil.
3 Drop the leaf in the boiling water for one or two minutes.
4 Turn off the hot plate.
5 Pour ethanol into a boiling tube. Use as little as possible, just enough to cover the leaf. Use forceps to remove the leaf from the water, and carefully put it into the ethanol.
6 Stand the boiling tube in hot water. What do you observe about the ethanol? Explain what happens.
7 When the leaf is mostly white, gently remove the leaf from the boiling tube with the forceps. Wash the leaf with warm water to soften it.
8 Spread the leaf out onto a white tile. Use a dropper to add some iodine solution onto the leaf. Observe what happens.
Caution: Put on your safety goggles when heating substances. Ethanol is a flammable liquid. Use the smallest volume possible and keep it away from naked flames.
