Coloured liquids showing density

Adding different amounts of sugar to water and dying it. Put the most dense at the bottom and then carefully pour the less dense liquids on top one at a time and we get pretty layers which diffuse together over time

 

Too much time on Practicals

It used to take ages to set up the circuit then, record some values and then graph them. I don't have time for this, so for the properties of resistors and bulbs and diodes the @pascoscientific voltage current sensor records everything in seconds and plots them. Perfect.

 

Whoosh Bottle

A-Level Chemistry one of the properties of Alcohol is that it burns - No far better get out the whoosh bottle and fill it with a bit of alcohol, shake and then ignite. Much more fun, and then lots of discussion on rockets.

fossil fish

Looking at a prehistoric fish fossil under a low-power microscope. Very little has changed in these millions of years. The students found this one more interesting than the ammonites

The not given formulae

 Just when the students thought they had learnt all the rules in the A level Maths book, I gave them even more, followed by the 1/2 angle formula - all derived from the formulae they had learnt - but they weren't happy.

Nylon Rope Trick

Everyone has a favourite experiment, and this is one of mine. The look on the student's faces when the nylon is pulled from the interface.

Pour 5 cm3 of the aqueous diamine solution into a 25 cm3 beaker. Carefully pour 5 cm3 of the cyclohexane solution of the acid chloride on top of the first solution so that mixing is minimised. This is because the oil floats on the water layer. Do this by pouring the second solution down the beaker's wall or a glass rod.

The cyclohexane will float on top of the water without mixing.

Place the beaker below a stand and clamp it. A greyish film of nylon will form at the interface.

Pick up some of this with tweezers and lift it slowly and gently from the beaker. It should draw up behind it a thread of nylon.

Pull this over the rod of the clamp so that this acts as a pulley.

Continue pulling the nylon thread at a rate of about half a metre per second. It should be possible to pull out several metres.

The thread will be coated with unreacted monomer and maybe a narrow, hollow tube filled with monomer solution. Wearing disposable gloves is essential.

Making a salt from an insoluble metal oxide

Copper sulfate is often made because of its colour, but making white salts is just as good, just more difficult for the students to visualise, as the solution is not coloured. Therefore making Zinc Chloride is a bit more of a challenge. 

To make a salt from an insoluble metal oxide and an acid, the metal oxide must be reacted with the acid to produce a salt and water. The reaction can be represented by the following equation:

Metal oxide + Acid → Salt + Water

For example, if the metal oxide is magnesium oxide (ZnO) and the acid is hydrochloric acid (HCl), the reaction would be:

ZnO + 2HCl → ZnCl2 + H2O

In this reaction, the salt produced is magnesium chloride (ZnCl2).