Physical vs. Chemical Changes
Students use kitchen materials to look at changes and determine if they are chemical or physical changes.
This activity set is from the Grade 5 Ontario curriculum.
What You Need
Materials per student or pair of students
- 1 baggie with ~2 teaspoons of baking soda (Powder A)
- 1 baggie with ~2 teaspoons of baking powder (Powder B)
- 1 Baggie with ~2 teaspoons of corn starch (Powder C)
- 1 Alka Seltzer tablet broken into 2 ("Tablet")
- Recording sheet and instructions (in guide)
- 8 labelled cups per individual/pair of students. These cups have about 1/2 inch from the bottom and are labeled.
Materials per class
- 1 full container of vinegar (for the teacher to distribute) - Each student/pair requires 1/2 cup
- 1 film canister with a tight fitting lid - the ones where the lid fits inside the canister (for the teacher)
- 2 tsp baking powder in a separate bag for the demonstrator
- A spoon
- Safety goggles
- Large pie plate for catching the rocket liquid.
Guide:
See attached guide for alternative activity supply list for virtual learners.
Safety Notes
As a Let’s Talk Science volunteer, safety must be foremost in our minds during all activities. As STEM role models, volunteers must always also model safe science practices.
Always keep in mind the following precautions:
- Emphasize and demonstrate appropriate safety procedures throughout the presentation.
- Be professional but have fun.
- Keep workspaces clean to avoid tripping hazards.
- Allergens should have been checked before reserving the kit (e.g. allergies to latex).
- Activity Specific Safety: Remind students not to eat or drink anything in the experiments or to eat and drink while doing experiments. Also they are not to touch the liquids and then touch their eyes – this would be for the vinegar as it will sting their eyes. Alka Seltzer (the tablet) contains aspirin which can be harmful to children under 12.
What To Do
Introduction
- Discuss the difference between physical and chemical changes.
- Go over the safety rules of this workshop before handing out activity supplies.
Experiment Procedure
Distribute the materials, instructions and the recording sheet. Each student or pair of students will:
- Start with the set of cups labelled "AA", "AB", "AC" and "A-Tablet".
- Add "Liquid A" up to the line on each cup.
- Add 1 teaspoon (doesn't have to be exact) of "Powder A" to cup "AA".
- Observe what happens and record it in the correct column in the table. Based on their observations, have students predict whether there has been a chemical or physical change (or both) and why.
- Add 1 teaspoon of "Powder B" to cup "AB".
- Observe what happens and record it in the correct column in the table. Based on their observations, have students predict whether there has been a chemical or physical change (or both) and why.
- Add 1 teaspoon to "Powder C" to cup "AC".
- Observe what happens and record it in the correct column in the table. Based on their observations, have students predict whether there has been a chemical or physical change (or both) and why.
- Put 1/2 the "Tablet" into the cup labelled "A-Tablet".
- Observe what happens and record it in the correct column in the table. Based on their observations, have students predict whether there has been a chemical or physical change (or both) and why.
- Repeat this procedure with Liquid B and the cups that start with B.
Demonstration (Film Cannister Rocket)
- Place the pie plate on the floor, in an area away from students and ceiling lights.
- Have students make predictions on what they think will happen if we added water and baking powder to a film cannister with a lid.
- Add 1/2 tsp of baking powder to a film cannister and fill it 3/4 full with water and tightly secure the lid and shake. Quickly place the film cannister on the flood, lid side up.
Discovery
The mystery liquids and powders in this experiment are:
- Liquid A is water (clear, colourless, odorless)
- Liquid B is vinegar (clear, colourless, smells)
- Powder A is baking soda (reacted with vinegar, formed lots of bubbles, did not react with water)
- Powder B is baking powder (reacted with vinegar and water, formed bubbles with both)
- Powder C is cornstarch (no chemical reaction but formed a 'goop' with water and vinegar)
- The tablet is alka seltzer (reacted and formed bubbles)
In the film cannister rocket, the water and baking powder react to form gas bubbles. The pressure from the gas causes the lid of the cannister to pop off!
Chemistry is the study of matter and how molecules interact. Chemistry helps us understand the world around us and our own bodies. We use chemistry for many things, from baking a cake to making medicine to take when we are sick. It is important to understand how matter will behave since it is always interacting.
- If the workshop is being facilitated virtually, show students a video of Elephant Toothpaste (or other chemical reaction) instead of the film cannister rocket demonstration.
What's Happening?
The mystery liquids and powders in this experiment are:
- Liquid A is water (clear, colourless, odorless)
- Liquid B is vinegar (clear, colourless, smells)
- Powder A is baking soda (reacted with vinegar, formed lots of bubbles, did not react with water)
- Powder B is baking powder (reacted with vinegar and water, formed bubbles with both)
- Powder C is cornstarch (no chemical reaction but formed a 'goop' with water and vinegar)
- The tablet is alka seltzer (reacted and formed bubbles)
In the film cannister rocket, the water and baking powder react to form gas bubbles. The pressure from the gas causes the lid of the cannister to pop off!
Why does it matter?
Chemistry is the study of matter and how molecules interact. Chemistry helps us understand the world around us and our own bodies. We use chemistry for many things, from baking a cake to making medicine to take when we are sick. It is important to understand how matter will behave since it is always interacting.
Investigate further
- If the workshop is being facilitated virtually, show students a video of Elephant Toothpaste (or other chemical reaction) instead of the film cannister rocket demonstration.