Incr-Edible Science

Having four young girls and at least two of them being passionate about being in the kitchen, I thought I would take a bit of time and create a curriculum that not only teaches my children how to cook but also teaches them why ingredients work as they do.  The science of cooking, if you like.  I hope this will enable them to be proficient in the kitchen, able to substitute ingredients intelligently and also to have the joy of  understanding how to create their own recipes.  My son will also enjoy it because anything scientific floats his boat!

This kitchen science is now affectionately known by all in the house as ‘Incr-Edible Science’

 

We will start with the science of Bicarbonate of Soda, the main reason being that the same week the little ones will be experimenting with bicarb and colours so I thought there was a nice over-lap.

We started with a lesson about atoms and molecules from the Macaulay book above.  I got this idea from Julie at highhillhomeschool.  I read the atoms and molecules chapter and we started building some atoms first and then molecules.  I tried to focus on atoms and molecules I knew we would use in our Incr-Edible science.  The marshmallows were the electrons and the coloured jelly sweets represented different nuclei.  The toothpicks were there simply to hold everything together:

Hydrogen atom (atomic number=1)
Hydrogen atom (atomic number=1)
Oxygen atom (Atomic Number=8)
Oxygen atom (Atomic Number=8)
Water Molecule-One Oxygen atom, sharing electrons with two Hydrogen atoms to complete all their outer shells)
Water Molecule-One Oxygen atom, sharing electrons with two Hydrogen atoms to complete all their outer shells

Then they tried to build a Sodium Bicarbonate compound.  First I wrote its chemical equation on the board and asked them to tell me the atoms in each compound and the proportions:

DSC_0642They seemed to understand this no problem.  I asked them to build each atom and to try to work out how they react together to form the Sodium Bicarbonate compound (they had read about ions and compounds in the Macaulay book).  At first they built the sodium atom (atomic number=11) and then worked out correctly (possibly by luck?) how the Bicarbonate was formed:

Sodium atom (top left) sitting next to the Bicarbonate molecule)
Sodium atom (top left) sitting next to the Bicarbonate molecule)

They noticed that the Sodium, if it shared its electron, still wouldn’t have a full outer shell it needed for stability.  They knew then it needed to give its electron to the Bicarbonate, thus ensuring all outer shells were complete:

The Sodium atom gives up the single electron in it's outermost shell
The Sodium atom gives up the single electron in its outermost shell

I asked the children what the Sodium atom was now called.  They struggled to understand what I was asking.  I got them to count the protons in the Sodium (atomic number=11 so there were 11 protons) and to count how many electrons (given one to the Bicarbonate  so was left with 10)  I then asked how this would affect the charge of Sodium – was it more positive or negative, and by how much.  They understood and replied that it now had a positive charge of one.  L10, who understood everything really well, remembered that an atom with a charge was called an ion:

Sodium ion
Sodium ion

I asked what charge the Bicarbonate would have.  They counted and found it had a negative charge of one having gained an extra electron from the Sodium:

Bicarbonate ion
Bicarbonate ion

I asked them to think about whether the Sodium ions and Bicarbonate ions would be close together or far apart.  They all agreed close together as each ion had an opposite charge and would therefore be attracted to each other.  Sodium bicarbonate is a chemical compound more commonly known as baking soda.  It is a white, crystalline salt which is soluble in water.  They checked its solubility:

Stirring the Sodium Bicarb into water:
Stirring the Sodium Bicarb into water:

They found it dissolved:

Water now clearer after stirring
Water now clearer after stirring

I asked what was happening to the ions.  T11 remembered that in water they separated and reacted with the water.  I asked them to concentrate on the bonds, looking at those which might be broken, those which might stay the same and those which might be made.  I taught them that the Sodium Bicarbonate would separate into Na ions and HCO3 ions and the HCO3 ions would abstract a proton from water.  This will form carbonic acid (H2CO3) which naturally decomposes to form CO2 gas and water:

NaHCO3 + HOH —>  Na^+1 (aq) +  OH^-1 (aq)  + H2CO3 (aq)

H2CO3 (aq) —>  CO2 (g)  +  H2O (l)

NaHCO3 + HOH —>  Na^+1 (aq) +  OH^-1 (aq)  +  CO2 (g)  +  H2O (l)

Sodium Bicarbonate plus water.....
Sodium Bicarbonate plus water…..
....equals
….equals Sodium ions, Carbonic acid and Hydroxide ions
....And the Carbonic acid breaks down into Carbon Dioxide and water
….And the Carbonic acid breaks down into Carbon Dioxide and water

I left this preliminary lesson at that and told them they could eat our chemistry lesson!

Next time I planned to go into acidity and alkalinity, potential Hydrogens and hence the reaction in the kitchen between the alkaline Sodium Bicarb with an acid such as lemon (to produce lemonade), buttermilk (in bread to produce the leavening for soda bread) and glucose syrup (to produce the holes in honeycomb)  We would then get down to the real fun of making all these and carrying out a little of our own experimental tampering with all the recipes to see how changes might affect the outcome.  Lots of fun ahead!

17 comments

  1. What a great way to do a hands-on demonstration of atoms! My Dad, a chemist, used to use shish kebab sticks and styrofoam balls when he taught the enginerring students at university. Your version looks much tastier!

  2. That is why you ask me to go out with the little ones! I will have to bear that in mind and get them a treat while we are out

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