Through observation and experimentation, students will continue to differentiate between qualitative and quantitative properties.

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Begin Investigation Two by reviewing what was learned in Investigation One. Pose the following questions to assist students in reviewing qualitative and quantitative properties of matter and their uses in chemistry:

What is a property? Student answers may vary. Students should indicate that a property is a characteristic of matter that can be described or measured.

What is the difference between qualitative and quantitative properties? Student answers may vary. Students should indicate that qualitative properties are properties that describe matter but generally are not measured. Quantitative properties are properties of matter that can be measured.

What are some examples of qualitative properties? Student answers will vary. Students should cite examples such as color, texture, composition, shape, and state of matter.

What are some examples of quantitative properties? Student answers will vary. Students should cite examples such as quantity or mass. Other examples that may be given by students include length, volume, and weight.

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Provide an opportunity for students to practice identifying an object by its quantitative and qualitative properties. Select an item in the classroom to use for the activity and encourage students to ask questions about the qualitative and quantitative properties of the object to help them identify it.

1. Write the headings Qualitative and Quantitative on the board.

2. Explain that students will take turns asking you questions about the object’s properties:

a. After students ask the question and receive an answer, they must identify the property as being either quantitative or qualitative.

b. Students will then list the property under the appropriate heading on the board. If desired, the instructor may choose to manage the list instead.

Use the following example to help explain the activity:

• The object to be identified is the door to the classroom. Student A might ask: “What color is the object?”
• The instructor would reply: “The object is light brown. What type of property is color?”
• Student A should respond: “Qualitative” and write “light brown” under the appropriate heading.
• Student B asks: “What is the object made of?”
• The instructor would reply: “Wood. What type of property is composition?”
• Student B should reply “Qualitative” and write “Wood” under the heading.
• Student C might deduce that the only objects made of wood in the classroom are the desks and the door, and ask: “How many legs does it have?”
• The instructor would reply: “None. What type of property is “number of legs”?
• Student C should reply: “Quantitative” and write “no legs” under the appropriate heading.

Continue the process until a student correctly identifies the chosen object. Direct the students to study the lists of properties under each column. Pose the following questions:

Could you have identified the object from only its qualitative properties? Student answers may vary. Students should indicate that it is unlikely that an object or substance can be identified solely from its qualitative properties.

Could you have identified the object from only its quantitative properties? Student answers may vary. Students should indicate that it is unlikely that an object or substance can be identified solely from its quantitative properties.

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Remind students that in Investigation One they compared different samples of matter using a pan balance and triple beam balance. Use the following questions to reinforce the concepts of mass and quantitative properties:

Were you able to determine the exact amounts of matter in the samples using the pan balance? Students should indicate that although they were able to determine which samples were lighter or heavier than others, they were unable to determine the exact differences between amounts of matter using the pan balance.

Why not? Student answers may vary. Students should demonstrate an understanding that the design of the pan balance generally limits its use to comparing the relative amounts of matter in objects because it lacks a scale to indicate exact quantities. Some students may suggest that they could use the pan balance with a set of calibrated masses to determine the exact mass. Although this is true, in many cases it would be difficult because calibrated masses cannot be split.

What tool did you use to measure the difference in the amounts of matter between the metal cube and the woodblock? Students should indicate that they used the triple beam balance to measure the difference in the amounts of matter between the metal cube and the woodblock.

What property did you measure using the triple beam balance? Students should indicate that they used the triple beam balance to measure mass.

Is mass a qualitative or a quantitative property? Why? Students should indicate that mass is a quantitative property because it can be measured.

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Conclude this part of the investigation by explaining that students will continue their investigation of the mass of their samples from Investigation 1, including baking soda and water.

Ask students: Although you did not determine the mass of the samples of baking soda and water in Investigation 1, what predictions would you make about the mass of each? Why?

Encourage students to think about what a Prediction is and the things students should think about when they are going to make a prediction. Predictions are ideas about what you expect to find.

What might you expect to find about the mass of baking soda and water from your experiments with the pan balance? Encourage students to use the phrase, “I predict” in their answers. Students should predict that the water would have a greater mass than the baking soda based on the results of their comparison using the pan balance. When the two were compared using the pan balance, the water sample was heavier than the baking soda sample.

Pose the following questions to students and encourage students to share their predictions with the class. Encourage students to think about the differences between the metal cube or woodblock and the baking soda and water, including whether the baking soda and water can be placed on the platform of the triple beam balance as they make their predictions. Again, encourage students to use the phrase, “I predict” in their answers.

Will you be able to measure the mass of the baking soda and the water? Student answers may vary.

How will you measure the mass of the baking soda and the water? Student answers may vary.

Would changing the amount of matter in a sample change the mass of the sample? Student answers may vary.

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