Chemical substances in foods

Step 1 Activity:
Baking soda and baking powder

Description and purpose of the activity

In this activity four experiments are presented where we use baking soda and baking powder in order to study chemical reactions. In each experiment we change a different factor (variable) and we observe how the change of each factor affects the chemical reaction. The purpose of this activity is to comprehend how factors like reactants’ purity, reaction’s temperature and reactants’ concentrations affect a chemical reaction.

Apparatus

• 3 plastic bottles (500 mL)
• 3 glasses or plastic cups
• Balloons
• 1 teaspoon
• 1 tablespoon
• 1 funnel
• Microwave or hotplate
• 1 black permanent marker

Ingredients - Materials

• Baking soda
• Vinegar
• Water
• Baking powder

Procedure

Factor 1: Reactants’ quantities

1. Take three balloons and place one teaspoon of baking soda in each one. Use a funnel or a piece of paper rolled into a funnel shape to help transfer the baking soda into the balloons.
2. Take three bottles (500 mL) and label them “Bottle 1”, “Bottle 2” and “Bottle 3”.
3. Put 1 tablespoon of vinegar into the bottle labeled “Bottle 1”, 5 tablespoons into the bottle labeled “Bottle 2” and 10 tablespoons into the bottle labeled “Bottle 3”.
4. Stretch a balloon over every bottle. Turn the balloon over so that all the baking soda drops into the bottle. Shake the mixture. You will observe that a gas is produced (carbon dioxide: CO2) and inflates the balloon.
5. Notice that the more vinegar there is in the bottle the more gas is produced.

Factor 2: Reaction’s temperature

1. Take three balloons and place one teaspoon of baking soda in each one. Use a funnel or a piece of paper rolled into a funnel shape to help transfer the baking soda into the balloons.
2. Take three bottles (500 mL) and label them “Bottle 1”, “Bottle 2” and “Bottle 3”.
3. Put 5 teaspoons of vinegar into the bottle labeled “Bottle 1” and put the bottle in a freezer for at least 1 hour. Put 5 teaspoons of vinegar into the bottle labeled “Bottle 2” and leave it in room temperature. Heat in a microwave a sample of vinegar, without boiling it, and put 5 teaspoons of hot vinegar into the bottle labeled “Bottle 3”.
4. Take the bottle out of the freezer and stretch a balloon over every bottle. Turn the balloon over so that all the baking soda drops into the bottle. Shake the mixture. You will observe that a gas is produced (carbon dioxide: CO2) and inflates the balloon.
5. Notice that the balloon of “Bottle 3”, which contains the hot vinegar, inflates faster than the others, unlike the balloon of “Bottle 1”, which contains the cold vinegar and which inflates slower than the others.

Factor 3: Reactants’ concentrations

1. Take three balloons and place one teaspoon of baking soda in each one. Use a funnel or a piece of paper rolled into a funnel shape to help transfer the baking soda into the balloons.
2. Take three glasses and label them “Glass 1”, “Glass 2” and “Glass 3”. Put 1 tablespoon of vinegar in the glass labeled “Glass 1”, 1 tablespoon of vinegar and 2 tablespoons of water in the glass labeled “Glass 2” and 1 tablespoon of vinegar and 4 tablespoons of water in the glass labeled “Glass 3”.
3. Take three bottles (500 mL) and label them “Bottle 1”, “Bottle 2” and “Bottle 3”. Put 1 tablespoon of vinegar from “Glass 1” into the bottle labeled “Bottle 1”, 1 tablespoon of vinegar from “Glass 2” into the bottle labeled “Bottle 2” and 1 tablespoon of vinegar from “Glass 3” into the bottle labeled “Bottle 3”.
4. Stretch a balloon over every bottle. Turn the balloon over so that all the baking soda drops into the bottle. Shake the mixture. You will observe that a gas is produced (carbon dioxide: CO2) and inflates the balloon.
5. Notice that the balloon of “Bottle 1”, which contains the highest concentration of vinegar, inflates faster than the others, unlike the balloon of “Bottle 3”, which contains the lowest concentration of vinegar, and which inflates slower than the others.

Baking soda versus baking powder

1. Take two glasses and label them “Glass 1” and “Glass 2”. Put 1 teaspoon of baking soda in the glass labeled “Glass 1” and 1 teaspoon of baking powder in the glass labeled “Glass 2”.
2. Add 2 tablespoons of water in both glasses. You will observe that the baking soda dissolves completely in the glass, while baking powder, which is insoluble in water doesn’t dissolve (A turbid solution is created). Also a gas is produced (carbon dioxide: CO2), but only in the glass containing the baking powder (Foaming is observed).
3. Take two balloons and place one teaspoon of baking soda in the first one and one teaspoon of baking powder in the other.
4. Take two bottles (500 mL) and label them “Bottle 1” and “Bottle 2”. Put 3 tablespoons of vinegar in each bottle.
5. Stretch the balloon containing the baking soda over the bottle labeled “Bottle 1” and the balloon containing the baking powder over the bottle labeled “Bottle 2”. Turn the balloons over so that all the baking soda and baking powder drops into the bottles. Shake the mixtures. You will observe that a gas is produced (carbon dioxide: CO2) and inflates the balloons.
6. Notice that the balloon of “Bottle 2”, which contains the baking powder, inflates faster, its volume however is smaller.