dry ice

It's been a wee while since I've blogged...I've been busy sipping iced cooled drinks and lathering on layers of sunscreen....meanwhile family, friends and colleagues in Europe have been battling along with an insanely cold start to the winter, -17'C in Llysdinam, Wales.  Brrrrrr....how cold is that!

Experiments with dry ice must be done.  To not carry out experiments using dry ice with your students is to deprive them of a memorable and valuable learning experience.

As a lesson intro, a guaranteed attention grabber is to have a range of different sized beakers, conical flasks, round bottomed flasks etc set up on the teachers table, each containing hot or warm water and a few pieces of dry ice, a squirt of universal or other indicators such as phenolpthalein or methyl orange will add a range of colours.  After a couple of minutes put in a squirt of dilute NaOH which will neutralise the excess carbonic acid that has formed and watch the rainbow effect work its magic. The visual effects are stunning and memorable and open up a wide range of questions.  The younger students are then left with no doubts that you are indeed a typical "crazy" scientist!  If it's attention grabbers that you're after for the start of the year then please see my previous blogpost "flash, bang, wow attention grabbers"

quick pub quiz question: what film features the crazy scientist shown above?

Firstly, set up 2 glass petri dishes, one containing a few cubes of dry ice (solid CO2, sublimes at -78'C) and another containing a few cubes of wet ice (solid H2O, melts at 0'C).  This is useful for students realising why dry ice is named as such and is commonly used as a coolant because it conveniently "disappears" as opposed to leaving wet puddles of water that result when wet ice melts.

Secondly, click here for a set of 6 activities that your students can carry out in pairs.  Encourage the use of cameras, mobile phones or laptops to take photos so that students can reflect and comment on their experiences, then provide detailed scientific explanations for what they saw happening....

and don't feel that dry ice is restricted only to the younger ones, I put together this series of experiments using dry ice for an introductory lesson to IB (International Baccalaureate) Chemistry although it would work well as an intro for any examining board.

The series of introductory experiments are set out in the following categories

1) Macro: what can be seen eg changes in colours, states... 2) Sub-macro: what cannot be seen with the naked eye eg atoms, molecules, ions 3) Subject specific vocabulary eg aliquots, enantiomers 4) Text language eg Na, Pb, Cl- 5) Symbols eg aq, delta, dipole 6) Representational eg equations 7) Mathematical skills eg calculating uncertainties, percentage yield 8) Logical reasoning eg.working out concentrations, identifying mystery substances

Click here to download the Chemistry Introductory lesson activities, they work brilliantly as an intro lesson.

So which film?
Back to the Future of course, the mad scientist's name is Dr Emmett Brown or just Doc Brown.