Pyrotechnics

Disclaimer: I am a qualified and experienced Chemistry Teacher; I have done these demonstrations many times and I know what I am doing. I have also done a thorough risk assessment. Please don't try to copy me.

That aside, I hope you enjoy these videos.

1) Fireball on hand

2) Fireball with pure oxygen

Questions
1) (Key Stage 3) What are the energy transfers involved in a methane fireball?

2) (GCSE) Are the products identical when pure oxygen is used, compared to when the methane is ignited in the air only? Explain your answer (using equations if possible)

3) (A-level) An average methane fireball is 500dm³
a. How many moles of methane gas is this?
b. What mass of methane does this equate to?
c. How many moles of oxygen is required for complete combustion?
Show your working

Making an ester

Learning Objectives:

• To know the reactants needed to make an ester
• To be able to synthesise an ester

How to make an ester

Esters are aromatic chemicals, they have a smell.

Esters can be made to give different smells depending on what is used to make them.

Every ester is made from an alcohol and an acid

The acid used is a different acid to the catalyst which is concentrated sulphuric acid

We will use salicylic acid and ethanol to make an ester which is “Oil of Wintergreen”

 Method

·         Boil a beaker of water for a water bath

·         Take a boiling tube and add 5 cm depth of ethanol

·         Add a heaped spatula of salicylic acid (a powder)

·         See your teacher who will add some concentrated sulphuric acid (why is this?)

·         Place the boiling tube in your boiling water and remove the Bunsen burner (why do we remove the Bunsen burner?)

·         Leave in there for approx 10 mins

·         After 10 mins, pour the contents of the boiling tube into half a beaker of cold water

·         Smell it the oil which floats on top, but don’t go mental

 

This was my last lesson of the academic year with Year 9. A lovely class. I hope to teach them again.

Fireball on hand

A picture of me from a couple of years ago doing methane fireball. This happens quite often at the end of term - often whether I like it or not...

Solution X

Year 10 applied their knowledge of tests for anions and cations to discover the ions present in Solution X.

Solution X was a concoction of a metal salt solution, with other chemicals. It was a blue solution.

Test 1. 1 M sodium hydroxide solution was added to give a brown precipitate showing the presence of Iron (III)
Test 2. The addition of silver nitrate solution gave a white precipitate showing the presence of Chloride.
Test 3. Solution X turned blue litmus paper red: it was acidic and so contained Hydrogen ions
Test 4. Solution X was heated with aluminium foil and 1 M sodium hydroxide solution. The gas given off turned red litmus paper blue, because ammonia gas was released. Therefore the solution contained nitrate ions.

The class accomplished this fairy well, although surprisingly didn't all think to try test 3 given the starting equipment.

In the end every group identified the four ions and deduced I has mixed iron (III) chloride with nitric acid. However they couldn't account for the blue colour, perhaps because at IGCSE we don't learn how to test for blue food colouring

Methane Fireball

With less than two weeks worth of working days left to go before the summer holidays, you might say, why start a blog now.

Simple. I had the idea, I am excited about it and realistically this is not something I will want to do come September with the business entailed and possibly an inspection.

Anyway, my students often get treated to a mini pyrotechnics show at this time of year, with some challenging questions of course. The timeless methane fireball: in a tub; in the air; on my hand; with pure oxygen; and my favourite: in a 500ml plastic bottle. In the case of the bottle, the best bang is achieved when the correct amounts of each gas (methane and oxygen) are added.

My questions to you:
1) What would be the balanced symbol equation for the complete combustion of methane?
2) Using this equation, what volumes of methane and oxygen would I need in a 500ml bottle for complete combustion to happen with no unused reactants?

I would love to have a video of me doing this, however since it is late and I can't find one in my archives, here is a link which is pretty much what I do.

An introduction to Chemistry Herald

This blog has been designed with my students in mind. I want them to be able to read this blog if they missed a lesson, in order to catch up. I hope anyone will notice any errors on here, since I am only human. Spotting mistakes and correcting them is of course a key evaluative skill. As the school year progresses there can be a record of what they have learnt on here. I also hope to find links to relevant additional reading, including helpful videos, which may or may not be made by me.