Tuesday, 1 May 2012

SCIENCE: Soda Snake Firework

This is a fantastic visual and stirs up excitement as the children watch the carbon snake grow.  Here's how to try it out yourself, but please be careful.  This does require adult supervision and goggles or eye glasses.



To make a soda snake you will need:
  • Sand
  • Isopropanol alcohol - rubbing alcohol will do, or lighter fluid.
  • Bicarbonate of soda - sometimes known as baking soda
  • Sugar
  • A heat proof surface
  • A bowl
  • Matches or a lighter

PLEASE DON'T FORGET TO WHERE EYE PROTECTORS! 

STEP ONE

Place a small mound of Sand on your heat proof surface

STEP TWO

Press your finger on top of the mound to create an indentation large enough to sit a golf ball in.

STEP THREE

Pour 25ml of isopropanol into the dent.  Do this very carefully so the rim is covered with it as well as inside the indent.

STEP FOUR

Mix 1 teaspoon of bicarbonate of soda (baking powder if you are in the US) with 4 teaspoons of icing sugar (powdered sugar).

STEP FIVE

Carefully pour the powder mixture into the dent on top of the isopropanol.  Try not to disturb the sand.

STEP SIX

Light the mound with a match or using a lighter.  When you do this touch the flame to the powder mixture. Light all around the rim to help form a snake like shape.
 Watch and see what happens…  It should look like a snake growing out of the mound.

















Warning:

Do not under any circumstances pour any more alcohol on the mound whilst the reaction is taking place, as isopropyl alcohol is highly flammable.

DO NOT PERFORM THIS EXPERIMENT WITHOUT A RESPONSIBLE ADULT, SAFETY GOGGLES AND PROTECTIVE CLOTHING.

Questions to ask:

  • What is fueling the fire?
  • How does the snake appear to grow from nothing?
  • What gas is produced? How do you know?
  • Is the process reversible or irreversible?

The fire is being fuelled by the Isopropyl alcohol.

What we are seeing happen is the sodium bicarbonate (NaHCO3) breaking down into sodium carbonate (Na2CO3), water vapour (H2O) and carbon dioxide (CO2).  The black snake that it leaves behind is Carbonate with black carbon particles.

Also when the sugar is burning in oxygen it produces water vapour and Carbon dioxide.

If you want to understand it further: 

  • What are the two products of the reaction? 
  • Can you think what the chemical equation would be?
2 NaHCO3 -> Na2CO3 + H2O + CO2
C3H7OH + 3 O2 -> 2 CO2 + 3 H2O
  • What links are there to the dehydration of sugar?
Sugar is a carbohydrate, so when you remove the water from the molecule, you're left with  carbon. This process occurs due to oxidation due to the reaction with the oxygen in the air. 

What has actually happened?

The baking soda releases carbon dioxide when heated above 50 degrees C.  Burning the alcohol creates a heat that is hot enough to caramelise the sugar.  This processes is what gives the snake it's black colour.

So why exactly does the snake grow?

It's all to do with the pressure from the gas CO2 (carbon dioxide) that is both released from the bicarbonate of soda and the sugar.  This reaction will stop when all the alcohol has been burned.

This experiment can get very hot, so it is important that it is performed on a heatproof mat or heatproof surface. The reaction should be performed in a ventilated room. No smoke is produced, but the alcohol vapour has a tendency to smell.  The burning sugar smells lovely though!

WHEN THE EXPERIMENT IS OVER ENSURE YOU LEAVE IT FOR A GOOD 5 MINUTES TO ENSURE THAT IT IS ALL COOLED DOWN AND THEN, FEEL THE SODA SNAKE.  IT IS SAFE TO TOUCH AND YOU MIGHT BE SURPRISED AT IT'S TEXTURE!
TIPS:

Make sure that the sugar and baking soda fills the indentation evenly, otherwise your snake may appear with mutant legs and eyes! Making a narrow, deep indent in the sand with your little finger or a pencil will help to make your snake tall and slim.  

It can take a few tries to get it right.

Extensions
  • Add food colouring to the sugar and baking soda - does it make a difference to the colour of your snake?
  • Try different types of sugar: granulated, brown, caster and icing.  Which works best?
  • Try the experiment on a bigger scale. What is the longest class snake you can grow?
In life this relates to raising agents in cooking
When dissolved in water baking powder, which is partly made up of bicarbonate of soda, reacts with the water and releases carbon dioxide.

The most common use for bicarbonate of soda is in the baking of cakes and breads.  The gas it releases, CO2, gives the light spongy texture we all know so well.  You can look closely at a piece of bread or cake and you will notice all the holes - this is where the carbon dioxide was produced!

2 comments:

  1. Replies
    1. Mixing the bicarbonate of soda and icing sugar together - thank you for pointing out that I hadn't made it clear feedback is so helpful. It's always lovely to hear from a reader. I hope you enjoy some of my other experiments too!

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