Summary Add candies to a baking soda solution, to confirm or predict which ones are the sour and regular candies. Science content Biology: Sensing, Organ Systems (4, 5, 6) Chemistry: States of Matter, Properties of Materials (K-7) Chemistry: Atoms, Molecules (3-7) Chemistry: Chemical Changes (2, 7) Science competencies (+ questioning + manipulation + others that are in every activity) Questioning/predicting: predicting (1 up), hypothesizing (7) Planning/conducting: data collection/recording (K up) Planning/conducting: fair testing and controlling variables (5 up) Processing/analyzing: classifying data, finding patterns (1 up) Evaluating: inferring (3 up) Lessons activity is in Sour chemistry Foods Chemistry Materials candies of the same type, some sour, some regular tray with wells e.g. paint tray or ice cube tray baking soda small scoop or coffee stir stick water in a squeeze bottle Procedure The best candies to use are the ones that look the same in regular and sour form. Regular skittles are smooth whereas sour skittles have acid crystals on the outside so they look quite different. Some chewy candies (e.g. fuzzy peach have sugar crystals on the outside, so they look similiar in regular and sour form. Explain/review with students that anything sour will have a chemical reaction with baking soda, and make bubbles. Students use the coffee stir stick to add a small scoop of baking soda to each of several wells of their tray. Add water into the wells and stir, to dissolve the baking soda and make a concentrated baking soda solution. Distribute candies (or a cut piece of a candy if they are large) to the students. If they are indistinguishable from each other, they should be labelled A, B etc. Students add a different candy to each well of their tray, and look at any bubbles formed. They should decide which candy gives off the most and least bubbles. Then they can predict with candy is the most and least sour. Taste to check! If not done already, discuss the chemical reaction: The baking soda (HCO2) reacts with the H atoms of the sour candy coating/inside to make carbon dioxide (CO2) gas. Students can use molecular models to figure out the reaction: give them the starting molecules, ask them to make water (H2O) and figure out what other molecule is made. When they use up all the atoms and bonds, and fill all the holes on the atoms, they should arrive at CO2, which is a gas, and makes the bubbles that they see. Grades taught Gr 4 Gr 5 Gr 6 Gr 7
