D. Crowley, 2007

Obtaining Reliable Results

To obtain reliable results, and to record these appropriately

Friday, May 5, 2023

Recap - Mass Of Product

What can you say about the overall mass of product(s) that forms in a reaction (in comparison to the mass of the reactants)

I.e. in a reaction do you get a greater reactant mass; a greater product mass; or does the mass stay the same?

Remember the mass of the product(s) is exactly the same as that of the reactants

We do not lose, nor do we gain any mass

Experiment

Today you are going to be assessed for your accuracies during an experiment

This assessment is based on your ability to heat metals safely, record appropriate results, and obtain reliable results…

Outcome

You are going to heat magnesium in the air

This will react with another element, and form a compound

You will need to record the mass of the compound formed, as well as that of the reactants you originally used…

Forming A Compound

On your sheet write down the word and symbol equation for reacting Magnesium (Mg) in the air. Also highlight where the reactants and products are (which side of the arrow)

reactants products

magnesium + oxygen magnesium oxide

2Mg + O2 2MgO

Forming A Compound

Secondly write a risk assessment (this can be bullet pointed) - what safety precautions should we take; are we using dangerous apparatus; how should we heat the Magnesium; do we need to avert our eyes etc…

Normal laboratory rules apply (I.e. sensible behaviour, hair tucked away, safety goggles on, chairs and bags clear, working space free from clutter…

We also need to be aware of the heat from the Bunsen burner - safety flame when not being used; heat proof mat down

The Magnesium also lets off a very bright light when burnt - this should not be directly stared at

Forming A Compound

Finally write down your method - you need to be as accurate as possible in finding the mass of the product magnesium oxide

How will your find the mass of reactants / products? How can we minimise product loss? How long will you heat for? Will you repeat your experiment?

Equipment to use

You have at your disposal: - Bunsen; heat-proof mat; string; stop-clock; balances;

ruler; clay triangle; tongs; tripods

Remember: - How will your find the mass of reactants / products? How can we minimise product loss? How long will you heat for? Will you repeat your experiment?

Method

Follow these steps, and record your results

There is a theoretical mass you can produce - prizes for pupils closest to this…

Method

1) Set up your equipment - Bunsen; heat proof mat; crucible & lid; balances; clay triangle; tongs; stop clock; tripod

2) Get a piece of magnesium, and place this in the crucible. Weigh the magnesium and the crucible + lid - record this

3) Place the magnesium in the crucible, place the lid on and heat for a given time (~2 minutes)

4) Let the crucible cool down, then re-weigh the crucible + lid (+ the magnesium oxide inside it) - record this

5) Repeat (at least three results)Make sure, once you have all your results, they are given into the class data so we can see who was most accurate!

Findings

Once you have your results, work out if your mass increased / decreased

Make sure you place your results on the class computer

Can you explain why the mass increased or decreased?

How could you increase your yield - i.e. how can you improve this experiment?