Is this a Physical or a Chemical Reaction?

Materials for Each Group

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Is this a Physical or a Chemical Reaction?

  • 1 Clear plastic soda or water bottle
  • 50 mL of vinegar
  • 1 Graduated cylinder
  • 1 Medium balloon
  • 1 Funnel
  • 2 Teaspoons of baking soda
  • Balance

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Is this a Physical or a Chemical Reaction?

Procedures

Measure 50 ml of vinegar with a graduated cylinder.

Measure the mass of a plastic bottle using a balance. Record in Table 1.

Pour the 50 ml of vinegar into the plastic bottle. Calculate the mass of the plastic bottle plus the vinegar. Then, use the balance to find the actual mass. Record in Table 1.

Using the information in Table 1, calculate the mass of the vinegar by subtracting the mass of the bottle from the bottle and vinegar together.

Measure the mass of an empty balloon. Record in Table 2.

Using the funnel, carefully pour 2 teaspoons of baking soda into the balloon.

Predict the mass of the balloon plus baking soda. Then use the balance to find the actual mass. Record in Table 2.

Using the information in Table 2, calculate the mass of the baking soda by subtracting the mass of the balloon from the mass of the balloon with baking soda.

Table 1: Bottle Data

Material / Mass
Plastic bottle / ______g
Plastic bottle with vinegar / ______g
Vinegar / ______g

Table 2: Balloon Data

Material / Mass
Balloon / ______g
Balloon with baking soda / ______g
Baking soda / ______g

Twist the balloon to keep the baking soda inside the top of the balloon.

Without spilling any of the baking soda, stretch the mouth of the balloon over the mouth of the bottle.

Looking at tables 1 and 2, calculate the total mass of your set-up (bottle + vinegar + balloon + baking soda). Record in Table 3.

Verify calculation by measuring the mass of your set-up with a balance. Record in Table 3.

Have one person hold the bottle as another turns the balloon completely upright, so that the baking soda inside the balloon pours into the bottle with the vinegar. Observe what happens and record your observations below:

Draw your Set-Up before adding baking soda / Draw your Set-Up after adding baking soda
Picture should have a deflated balloon attached to the bottle. / Picture should have an inflated balloon attached to the bottle.
  1. What two substances combined in the experiment? ______

The vinegar and baking soda combined.______

  1. Did the baking soda and vinegar make a reaction? How do you know?

Yes, the bubbles and the inflated the balloon are evidence of a chemical reaction.______

______

______

  1. Did the reaction form a new solid, liquid, or gas? Explain.

Students should note the formation of gas. They may also report seeing the formation___

of a new solid and a new liquid.______

______

  1. Did the temperature of the bottle change? Explain.

Students should feel that the bottle feels cooler during the reaction______

______

______

  1. What evidence is there that a chemical reaction has taken place? ______

Bubbles indicate that a gas was formed causing the balloon to expand.______

The cooler temperature of the bottle is another indication that a chemical reaction has__

Taken place.______

Carefully place the bottle (with the balloon still attached) on the balance. Record this mass in Table 3.

Table 3: Data of Set-Up

Mass of Set-Up Before
(calculated) / Mass of Set-Up After
(measured)
Plastic bottle + Balloon / ______g
Vinegar + Baking Soda / ______g
Total / ______g / ______g
  1. Compare the total mass of your Set-Up before and after. What do you observe and what can you explain? ______

Answers will vary but the mass of the products should be approximately the same as___

the mass of the reactants.______

______

______

  1. Explain how this experiment shows that the mass of an object is equal to the sum of all its parts.

The masses of reactants and products should be the same.______

______

______

  1. Give two reasons why the mass of the reactants in your experiment may not be exactly equal to the mass of the products.

Answers may include: human error, spilled some of the baking soda, did not read______

balance correctly, balloon was not on tightly so some of the gas escaped.______

______

______

Teacher Notes:

During the exercise, make sure to ask probing questions and find out what students understand from the process. This experiment is not designed to solve a problem statement, but to use the Nature of Science process to make observations, gather data, and reflect on the information collected.

In a chemical reaction, the substances that you start with (the reactants) are different from the substances you finish with (the products). In this activity, the reactants were the baking soda (a pure substance) and vinegar (a solution). The products were a mixture of water, carbon dioxide, and a kind of salt called sodium acetate. Also, you have learned that the sum of the reactants (the Set-Up Before) was equal to (almost) the sum of the products (the Set-Up After). Some of the reasons why the two might not have been exactly equal are that (1) some of the carbon dioxide escaped, (2) the pan balance was not completely accurate, and (3) human error during the measuring of mass of the substances occurred.

Examples that a chemical reaction is taking place are (1) color change, (2) formation of a gas, (3) formation of a solid, and (4) changes in temperature as a result of energy exchange.

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