Chemicals
are made up of atoms, atoms contain ions – ions are electrically charged
particles, they are formed when atoms loose or gain electrons. Ions of alike repel and opposites attract,
much like magnets!
Electrons
are particles of negative change.
In
an atom, electrons form a negative charge that balances out the positive charge
of the protons in the atomic nucleus.
Electrons
are extremely small, they are about 1000 times smaller than a proton.
If
you truly want to understand what is happening in this experiment you need to
know which ions are produced by alkalis and which ones are produced by
acids. You will also need to know the ionic
equation for neutralisation which I have included at the end.
One of the
safest experiment you can perform which will give you the result you need is
Citric acid and Bicarbonate of Soda and this is how to perform your experiment...
You
will need:- Goggles
- 2 test tubes –Test tube stoppers
- 2 pipettes – if you don’t have pipettes you could use a teaspoon instead.
- A petri dish
- Citric Acid
- Bicarbonate of Soda
-
pH
paper
-
Water
STEP ONE
Put your goggles on then add
half a test tube of water to two of your test tubes.
STEP TWO
Add
5ml of citric acid to one test tube.
STEP THREE
Add
5ml of bicarbonate of soda to the other test tube.
STEP FOUR
Put your
stoppers on your test tubes and gentle swirl them a bit until all has been
dissolved in the water.
Now they are aqueous! Aqueous is a term used in science meaning a substance is dissolved in water.
STEP FIVE
Using
your pH strips first test the citric acid and then the bicarbonate of
soda. Write down your results if you
like. I like to keep a science notebook
for this.
STEP SIX
Using
your pipettes and the petri dish (or, as I have said in the list above an old
lid or small dish) Take a small amount, about 3ml of the citric acid and put it
into the petri dish.
STEP SEVEN
Now
using a different pipette extract some of the bicarbonate of soda from one test
tube, try 1ml at a time and put it into the petri dish.
STEP EIGHT
STEP NINE
If
it’s still an acid, add another 1ml of bicarbonate of soda and repeat STEP EIGHT. Keep repeating these steps until the solution
becomes neutral.
Your science notebook, if you wish to use one should look something like this for this experiment...
STEP THREE in our science notebook did look alkali until someone touched the pH strip, but this gives you an idea.
Other options for this experiment:
If you
don’t have any test tubes you can use glasses or plastic beakers instead.
Instead
of the petri dish you could use a third test tube or an old lid from a jar.
Citric
acid and Bicarbonate of soda
Citric
acid is a tripotic acid – this means it’s an acid that has three ionisable
hydrogen atoms in each molecule – therefore the ratio between citric and bicarbonate
of soda is 1:3.
The equation will look
something like this…
C6H8O7
+ 3NaHCO3 = C6H5O7Na3 + 3 CO2 + 3 H2O
Citric acid + Bicarbonate of soda = sodium citrate + carbon dioxide + water
Another neutralisation you might want to try …
Hydrochloric
Acid and Calcium hydroxide
Ca2(OH)
+ 2 HCl = 2 Ca(Cl)2 + 2 (H)2O
We
use neutralisation in the real world to balance out the acidity in lakes and
soils caused by acid rain. To do this we
use the alkali, Calcium hydroxide.
This
method is also used by gardeners, acids are also added to the soils sometimes
if an acidic soil is needed. You might
like to check out my experiment: Soil pH Test
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