ShareChanging Matter - Conserving Mass
Recall that a chemical reaction has reactants which enter into the reaction. It also has products which are the substances that result from the reaction. Based on this information, you will be given the opportunity to prove that the amount of matter that enters the reaction is the same as the amount of matter that is found after the reaction.Be careful to follow all directions below so you are able to prove this fact! The mass that enters into a chemical reaction is equal to the mass that results from a chemical reaction! This reaction will allow you to observe color changes that result from a chemical reaction.
Materials:
- One small head of purple cabbage
- Knife or kitchen grater
- Five clear beakers
- Clear liquids (options: vinegar, sugar water, baking soda in water, soda, salt water, and water)
- Balance scale
- Graduated cylinder
Procedure:
- Cut or grate the purple cabbage into a large bowl.
- Add distilled water until the cabbage is completely covered.
- Allow this mixture to sit without being disrupted for one hour.
- Measure and record the mass of a beaker
- Add 50ml of one clear liquid to the beaker.
- Measure and record the mass of the beaker again.
- Follow the same procedure for each of the other four beakers.
- Measure the mass of the graduated cylinder
- 15 ml of cabbage juice into a graduated cylinder.
- Measure and the record the mass of the cabbage juice.
- Subtract the mass of the graduated cylinder to obtain the mass of only the cabbage juice.
- Add the mass of the beaker with the liquid to the mass of the cabbage juice.
- Pour 15 ml of cabbage juice to a beaker containing
one of your clear liquids.
- Make observations of color change.
- Measure and record the mass of the beaker again.
- Continue until you have completed the process for all five liquids.
Safety concerns: 
Be sure to follow all glassware, eye,
and chemical safety rules
that are specified by your teacher and in all general laboratory experiences.
As with all science lab activities, the most important safety rule is to follow all teacher directions.
Data:
| Sample 1 | Sample 2 | Sample 3 | Sample 4 | Sample 5 | |
| Clear liquid being tested | |||||
| Measured mass of beaker | |||||
| Measured mass of beaker and 50 ml. clear liquid | |||||
| Mass of clear liquid minus mass of beaker | |||||
| Measured mass of graduated cylinder | |||||
| Measured mass of graduated cylinder and 15 ml. cabbage water | |||||
| Measured mass of cabbage water minus mass of graduated cylinder | |||||
| Mass of clear liquid added with mass of cabbage water (done before adding in the experiment) | |||||
| Measured mass of beaker, clear liquid, and cabbage water after experiment | |||||
| Measured mass of clear liquid and cabbage water minus mass of beaker |
Analysis:
- Which kind of change was observed (chemical or physical)?
- How did the mass of each clear liquid added to the mass of the 15 ml. cabbage liquid compare to the actual measured mass when they were combined?
- What evidences of change did you observe in the experiment?
Extension:
The cabbage liquid acts as an indicator for acids and bases. Strong
bases will turn it yellow, mild bases will turn it green, weak will turn
it blue. Strong acids turn it red, more mild acids turn it pink. Based
on the experiment observations, which of your liquids were acids and which
were bases? Were any strong acids or strong bases?
