Starch Amylase Experiment

I made up a starch solution  with 1/4 teaspoon  of starch dissolved in about 100ml of water I used soluble starch but corn starch will do or even the water from boiling potatoes.
I had a failure with the experiment the last time I did it with a student so I tried the same chemicals again to test to see if they worked. Into the first tube I added some starch and a few mls of a 1% Amylase solution. Into the next tube I put the same amount of starch and 2-3 mls of spit - I know this enzyme works.

After 20mins I took a sample of each of the tubes and added a squirt of Benedicts reagent and placed in a beaker of near boiling water for a few minutes. The left hand tube with the commercial Amylase powder enzyme turned the brown colour - confirming that the enzyme was working and converted some of the starch to maltose.

The middle tube went green showing that the Amylase in my mouth worked - slower - but some Maltose was made.

The tube on the right with just starch and no enzyme did not change showing that Starch does not react with Benedicts solution and there was no Maltose present in the starch.

So the Amylase enzyme does work and does convert starch to Maltose which is a reducing sugar (the Benedicts Test)
My spit works too albeit slower.
Now why did this not work for the student? I have no idea.

Kipps Apparatus

I bought a Kipps apparatus to generate Carbon Dioxide Gas or Hydrogen Gas. I don't need very much or make it that often so gas cylinders are a waste of time. It is a fascinating piece of equipment which is so simple to use.The Kipps generator was invented in 1844 by Petrus Jacobus Kipp and was used throughout the rest of the 19th and the entire 20th centuries for making gases.  Kipp generators are still being used in some places even now because of their ability to make a gas and then stop and then to be turned on again.
The Kipps apparatus is used to make a variety of gases such as Carbon Dioxide, Hydrogen and Hydrogen Sulphide. This is often why the Kipps apparatus was often left in a fume cupboard in the back of a classroom for all to see.
To make hydrogen gas some granulated zinc is put into the middle vessel by removing the  stopper.
Acid is then poured into the top vessel which is connected by a glass tube to the bottom vessel.
When the chemist requires the gas the valve in the middle chamber is opened and this allows the acid in the top chamber to force by air pressure the acid in the lower chamber into the middle chamber. The acid mixes with the zinc and there is a reaction. The zinc reacts with the acid and generates hydrogen gas. If the valve is open then the gas is collected often under water into a gas jar.
When enough gas has been collected the valve is turned off. The pressure in the middle chamber starts to increase and pushes the acid out of the middle chamber back into the bottom and also into the top chamber. When all the acid has been removed the reaction stops because there is no longer any acid to react with the zinc.
The Kipps apparatus is very simple to use, interesting to understand how it works and gives a good insight to how old fashioned ideas are still good to use today

Convection Currents in a beaker of water

 One of my A level students yesterday had never seen convection currents in water, so I set up this simple experiment for him. Into a large beaker I poured some cold water and at the bottom I placed a small coloured crystal.
I heated the water with a burner and watch as the water heated,  the water coloured by the crystal rose up in the beaker - not straight as the books suggest but in a more spiral direction until they reached the top when they spread out even more.

The water showed that it was less dense than the water around it because it was hotter and therefore it was lighter and rose to the surface - albeit not in a quite vertical direction.

There we are warm water rises and disperses the heat around the beaker from the bottom to the top.