Do you ever cook or help to cook at home? There is a lot of science in cooking - all that mixing and heating - lots of chemistry and chemical changes going on. We’ll make scones today and investigate the chemistry happening in our recipe. And then we get to eat our experiment!
Recipe for scones on the board:
1/4 cup flour
1/4 teaspoon baking powder
1/16 teaspoon (pinch) baking soda
1/16 teaspoon (pinch) salt
2 teaspoons melted butter
1/8 cup buttermilk
Mix into a ball
Bake at 450F for 15-20 mins til brown
Each student adds the dry ingredients to the tub and mixes them together. Then add the wet ingredients and mix in with the spoon.
Pick up with the hands and mix more before moulding into a ball. Put on the tray and bake in the oven.
Tell students that in the oven the ingredients are mixing together and heating up, to make a cooked scone.
Some of these ingredients have a chemical reaction with each other to make something new, a gas. The gas pushes the dough up to make it rise.
To figure out which ingredients are making a gas, we need to know what that looks like (bubbles).
I have a challenge for you. Figure out which of these ingredients are making the gas by looking for bubbles when you mix them together. Use the wells of the paint tray for trying different combinations of ingredients. (Remind students to avoid contamination by using a new coffee stir stick to pick up and mix the ingredients for each trial.)
Add water as an ingredient to try mixing, as it is a component of the buttermilk.
Ask students to fill out the worksheet (attached) so they can remember which combinations made the gas.
If students are mixing many ingredients together each time, prompt them to only mix two ingredients, so that they can figure out which ingredients alone are needed to make gas.
Results should show these results with the fewest ingredients: the baking powder and water makes gas, as well as the (warmed) buttermilk and baking soda.
If time with older students: the chemical reaction happening can be shown with molecule modeals.
H (loose hydrogen atom, present in sour things) + HCO3 (baking soda) ---> H2O (water) + CO2 (carbon dioxide gas)
Hand out their scones.
Optional: hand out butter and knives (not necessary with buttermilk scones, but appreciated with the drier lemon scones).
Before they eat it, ask students to break their scone open, and look for the empty spaces, where the bubbles of gas were. The gas made by the ingredients mixing made bubbles, which got stuck in the dough and pushed it up to make it rise in the oven. Then the scone baked around them.