University of Virginia
Physics Department

## Indirect Measurement

A Physical Science Activity

2003 Virginia SOLs

• PS.1
• PS.3

Objectives

Students will

• describe the appearance and behavior of an unseen object by conducting controlled experiments;
• record and organize data;
• present experimental results in written form;
• describe a method to measure the properties of objects that are not readily visible.

Motivation for Learning

Driving Question

How can we describe the structure of objects we cannot see? Explain to students that atoms are extremely small. To give them an idea about how small, distribute to each student a piece of paper that is 8 ½ x11 inches. Instruct the students to rip the paper in half and set one half aside. Tell them to tear the remaining half in half again. The student now has two pieces of paper that are one quarter the original size. They should now tear one of these pieces of paper in half again. This process should continue until the remaining paper is too small to tear any further. Explain to the students that if they could continue this process sixty more times, they would have about a single atom from within the paper.

Background Information

Matter can be broken into smaller and smaller pieces. What happens to these parts of matter after they become too small for us to see or feel? To learn about them, we need a way to test their behavior and structure indirectly. When Ernest Rutherford tested the Plum Pudding Model of the atom, he could not see the atom or its parts. So, he tested the behavior of atoms when bombarded with alpha particles and found a small, positively charged region which he named the nucleus.

### Student Activity

Materials

• Several shoe boxes (or other unbreakable and sealable containers) with tops; write the mass in grams of the box and its top on the outside of the box
• Familiar and unbreakable objects such as balls, metal utensils, pencils, etc.
• Tape
• Balance
• 8 ½ x 11 inch paper (one sheet per student)

Procedure

1. Set up shoeboxes so there is one per student or per lab group. In each box, place a familiar and unbreakable object such as a pencil or rubber stopper. In some boxes, place several of the unknown objects to add variety. Seal the box with tape so the object cannot fall out of the box nor be seen by the student. Number each box and record the contents of each. Write the mass of the empty box and its lid on the outside of the box for student reference.
2. Distribute the boxes to the students after explaining the background information. Remind the students they may not open the boxes but must decide the identity of the object(s) inside by conducting tests on the box. Explain that all of the objects are familiar and unbreakable. Also explain that the students may want to conduct tests such as shaking the box and listening to the sound it makes or listening to whether it collides with other objects in the box. Tell the students they should also find the approximate mass of the object(s) by finding the mass of their box and the mass of the sample empty box. The tests they will conduct are listed on the "Student Data Sheet." Remind the students to record the number on the outside of the box on their data sheets. Some teachers may choose to make a 'bank' on the board of all items within the boxes and may include the masses of individual items so the students may be more exact in their deductions.
3. Allow the students to conduct the tests as outlined on the "Student Data Sheet." Encourage them to write careful and detailed observations in the space provided so they have an accurate record of the experiment. Also encourage them to think of additional tests to conduct. Space for student developed tests is included on the "Student Data Sheet".
4. When the students complete the data collection, tell them to decide what they think the boxed object is. Space for their conclusion is provided on the "Student Data Sheet."
5. At the teacher's discretion, students may open their boxes to check their conclusions. Or, teachers may reveal the contents without opening the boxes to avoid resealing them for other classes.

Data Sheet

Student Data Table

Box number: ______________

 Experiment Observation 1. Mass of the sealed box with the unknown object 2. Mass of an empty shoe box 3. Mass of the object (#1-#2) 4. The unknown object moves lengthwise within the box. 5. The unknown object moves crosswise within the box. 6. The unknown object moves up and down within the box. 7. The unknown object rolls within the box. 8. The unknown object collides with other objects in the box. 9. The unknown object is much smaller than the box. 10. The unknown object is almost as big as the box. 11. 12.

Questions

1. From your data, what do you think the object in the box is? Explain in the space below why you think this.

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

2. With your teacher's permission, you may open the box to look at the object. Was your conclusion in question 1 correct? If your conclusion was correct, explain which test or tests best allowed you to identify the object. If your conclusion was not correct, explain which test or tests made you conclude as you did.

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

Extensions

1. Carry out a similar exercise by dividing the class into teams. Provide each team with three identical boxes containing identical small objects. Each team will conduct tests similar to those conducted in the earlier experiment to determine the identity of the objects within the boxes. The teams earn points or prizes based on the accuracy of their conclusions.
2. Students identify a different but commonly found object from the ones used in the exercise and make a list of qualities such as the sound it makes, its mass, etc. They share their lists with one another to see if their classmates can determine the identity of the object they are describing.

Students with Special Needs

Students unable to manipulate the boxes independently can work with a partner or the class can be divided into groups. To maintain a more structured environment, do not have the students trade boxes.

Click here for further information on laboratories with students with special needs.

Assessment

1. Students complete the data record and answer the questions explaining how they drew conclusions on the identity of the object(s).
2. Students look for other examples in their lives where they must use indirect data collection methods. (Example: Determining a burner on a stovetop is hot because it is red, not because one has touched it.)