Chemistry in the Kitchen

Here is an extract from the Bake a Chemistry Cake  project:

Next time you bake a cake, consider this. The cake dough is not really a cake, but when it’s heated in the oven, a chemical reaction occurs and new bonds are formed. How does heat change things? When it comes to heat changing a chemical reaction, there are two types. One is “exothermic,” a reaction that produces heat, and the other is “endothermic,” a reaction that takes heat in. When you make a cake, you a producing an endothermic chemical reaction which changes batter to baked!

A few things can happen when you bake a cake. Some chemical reactions to keep in mind while doing this tasty experiment are:

1. Heat helps baking powder produce tiny bubbles of gas, which makes the cake light and fluffy.
2. Heat causes protein from the egg to change and make the cake firm.
3. Oil keeps the heat from drying out the cake.

 So the experiment is about doing it right and then doing it wrong.

Ingredients

• 6 tablespoons flour
• 3 tablespoons sugar
• 1 pinch of salt
• 2 or 3 pinches of baking powder
• 2 tablespoons milk
• 2 tablespoons cooking oil
• 1/4 teaspoon vanilla
• butter knife|
• 1/3 of an egg (*)

(*) Break the egg into a cup and beat it until mixed.  Pour the amount equally into the McDonalds ketchup containers.

Method

We made 4 little cakes as follows:  

1. One with all ingredients
2. One without the baking powder
3. One without the egg
4. One without the oil.

The batter pretty much all the same. The No Egg one looked more pale. The others were more yellow and it was white.  The No Oil one was harder to mix.

What did they look like?

 

1. The one with all the ingredients looked as expected … like a cup cake!
2. The one without the oil was a surprise. It had a nice hard oval top!
3. The one without the egg was paler and did not rise as high as the others.
4. The one without the baking powder did not look so bad?

What did they taste like?

1. The one with all the ingredients tasted OK
2. The one without Oil had a crunchy top and was dry like bread
3. The one without the Egg tasted floury
4. The one without Baking Powder tasted the same as the one with all ingredients?

So why was the one without the baking powder OK?  Because we’d used Self Raising Flour that already has baking powder in it instead of All Purpose (Plain) Flour which doesn’t.  So while it did not rise quite as high as the others it was pretty close.  Duh!  Have to try that one again!

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