exploding sodium?

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User: nikmumby

Today one of the teachers was doing group 1 metals with water and the sodium was way more reactive than the potassium. It was the same size (small) and it started out how you'd expect but then near the end of the reaction it exploded and sent sparks everywhere. Does anyone have any ideas why?
 

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User: HerschelTechnicians

I have been informed by my colleague that sodium is unpredictable. With potassium and lithium you know what is going to happen but with sodium, as the cleapss hazcard says, you cannot be sure. It is to do with the sodium keeping cool by skating around the surface of the water or if it stays still too long is can explode. Following the guidelines makes it safe no matter the outcome.
 

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User: lpreece

Have had sodium react so violently in the past that it has cracked then broken the glass bath.

If worried about its re-activity, use a small a piece as you can, plenty of safety screens, etc, and follow guidance.

Leigh....
 

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User: freda

We have had our sodium "crystallizing" on the glass trough around the edge of the water and on another occasion spitting at one of the teachers - different teachers, same sodium batch. We have not changed our methods and this has not happened before. We disposed of the rest of that sodium and started on a new block. Fingers crossed. We also reviewed our safety policy for the alkali metals.
 

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User: 007

We carry out the demonstration of alkali metals with water in the fume cupboard, so should this happen risk to the teacher and the students are kept to a minimum
 

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User: Jyeardly

like 007 we use a portable fume hood for protection of students (also cut down on asthma Ra's )
sodium (according to our retired Head of chemistry) can form a "super oxide" which can give an extra punch to the reaction
Don't know if its true or not but remeber to take care on the clean up if this is reported as there might be some unreacted bits around
 

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User: louise81

sodium is unpredictable - we have made a circular piece of perspex which we put over the trough whilst the reaction is taking place. Protection for the teacher and we also have a safety screen for the students who are 2m away. Its amazing how much alkali water is on the underside of the sheet when the reaction ends - otherwise this goes over the bench/demonstrator
 
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