Patterns in reactions, with reference to the periodic table
Practical activities which look at the reactions of different groups of elements are always exciting. This list provides some advice on carrying out some traditional demonstrations and ideas for practicals which which explore reactivity. The resources link to the following statements in the 2014 curriculum:
• how patterns in reactions can be predicted with reference to the periodic table
• the order of metals and carbon in the reactivity series
Visit the secondary science webpage to access all lists: www.nationalstemcentre.org.uk/secondaryscience
Links and Resources
This is an experiment that students can carry out for themselves. They react magnesium and calcium with dilute acid in order to determine how reactive the metals are. The experiment can easily be expanded by reacting the same metals with water. The reaction of magnesium with water is too slow to see but students will see effervescence if they use Bunsens to heat the water.
Alternatively leave a coil of magnesium at the bottom of a large beaker until the next lesson. Place an upturned funnel over the magnesium and collect the hydrogen obtained with a upside down test tube over the funnel. Next lesson you'll have enough hydrogen present to carry out the "pop" test convincingly.
Before starting work, students should be encouraged to think how they should record their findings. Alternatively provide a results table for students to complete. Having carried out the reactions, students should be able to predict how beryllium and strontium would behave.
This excellent film from Teacher TV is exactly what teachers need to enable them to demonstrate the reactions of groups I and VII and show how reactivity can be predicted. It’s full of detailed information about how to carry out the reactions and there are safety tips and advice that will enable teachers to feel confident that they can repeat them in front of a class.
If you haven’t tackled these reactions before, try them out on your own or with a technician before trying them with a class present.
Reactions of other elements are covered too and, as this film covers material from both Key Stage 3 and 4, teachers will want to choose carefully the reactions they use with their own students.
A further film from teachers TV, this time designed for students, provides an excellent follow up to these demonstrations and is provided below.
This film shows lots of dangerous reactions that students will love. It’s designed to complement the reactions of elements, particularly those in groups I and VII and it’s a perfect follow up to teacher demonstrations as in the resource above.
The film takes a tour around the periodic table and as well as consolidating the reactions teachers will have demonstrated it goes on to show reactions of the more dangerous elements that aren’t kept in school. It lasts about a quarter of an hour.
This isn’t a standard school demonstration but it’s worth trying if you fancy something a bit different, perhaps to make a fun end to a lesson on the alkali metals. In this film you’ll see how to light a match using small pieces of sodium or potassium by dropping water on to them. It’s probably a bit small scale for students to see clearly what is happening so use of a camera or visualiser to project the image onto a screen – just think carefully about where to put it so that it isn’t damaged by the reaction.
The halogens are generally too dangerous for students to handle but in this classic experiment from the Royal Society of Chemistry they can investigate some of their properties by using solutions in water. They then go on to examine displacement reactions and so confirm their reactivity.
If students have already had the physical properties of the halogens demonstrated then this experiment would make a good follow up. Encourage students to think about what the experiments tell them about the order of reactivity