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Activity

Scone chemistry

Summary: 
Students make individual soda bread "scones". While the scones are baking they experiment with the ingredients, mixing them together to find out which combinations make a gas.
Science content (2016 curriculum): 
Chemistry: States of Matter, Properties of Materials (K-7)
Chemistry: Atoms, Molecules (3-7)
Chemistry: Physical Changes, Solutions, Mixtures and Separating (2, 4, 5, 6)
Chemistry: Chemical Changes (2, 7)
Science topic (2005 curriculum connection): 
Physical Science: Properties of Matter (grade 2)
Physical Science: Chemistry (grade 7)
Lessons activity is in: 
Materials: 

Scone:

  • Recipe written on board or worksheet - two options below
  • Plastic tubs to mix in for each person
  • Metal spoons for each person
  • Flour – 1/4 cup per person
  • Salt - pinch per person
  • Baking soda – 1/8 teaspoon per person
  • Melted butter - 2 teaspoons per person
  • Buttermilk – 1 tbspn per person
  • Labelled bowls for all ingredients with its measuring spoon, for each table group
  • Buttermilk aliquoted into dixie cups for younger students
  • Tray for passing ingredients to each table
  • Toaster oven to fit all scones, with buttered baking tray
  • Sheet and pen to map names in oven
  • Timer for oven
  • Paint trays, one per student
  • coffee stir sticks
  • Optional: worksheet
  • Oven mit
  • Paper towels to put finished scones on
  • Butter and knives for each table (optional)

Scone ingredient experimentation:

  • Same ingredient tubs on tables, but with smaller measuring spoons for all. Note: warm the butttermilk slightly, so that a chemical reaction between it and the baking soda is evident
  • Ice cube or small paint tray per student
  • Toothpicks for each table to mix ingredients (use used mixing tub for waste)
  • Wooden stir stick per student for tasting
Procedure: 

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:

Buttermilk scones:
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.

Notes: 

Can test other sour ingredients (ketchup, vinegar, orange juice) with baking soda and find out which ones make bubbles.

Purchase molecule models online at Indigo Instruments https://www.indigo.com
One set to model the chemical reaction above requires:
2 hydrogen atoms #60110E (1 Hole 17mm White Atom) 45 cents each in 2017
3 oxygen atoms #60200E (2 Hole 105 Degree 23mm Red Atom) 59 cents each in 2017
1 carbon atom #60400E (4 Hole tetrahedral 23mm Black Atom) 67 cents each in 2017
6 bonds #61013E (Molymod Double-Triple Bonds) 19 cents each in 2017
Get at least one set per student pair and several extra atoms of each type and 10 or so spare bonds.
For 15 sets plus spares you'll spend about $100 with tax and shipping.

Grades tested: 
Gr K
Gr 1
Gr 2
Gr 3
Gr 4
Gr 5
Teacher: 
Ingrid
Teaching site: 
General Gordon Elementary Science Club
ingridscience afterschool
JEMZ+ After school science
After School Program at Elementary schools in New York City
Activity originally developed and delivered: 

The School at Columbia After School Class