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PDF Files for PrintingLesson 3-Explore: Let's Investigate Tooth Decay!



Exee holding an appleIn Lesson 3, students develop scientific inquiry skills by asking a question, conducting a simple investigation, using tools and observations to gather data, using data to explain their results, and communicating their results. Students use apples as models of teeth to investigate the process of decay. They discuss what might happen if the skin of the apple were punctured, and they set up a simple investigation to find out. Students suggest variables they might change, such as the number of holes, the size of the holes, and the environment of the apple, and compare their results with a control apple. They make and record observations and, after several days, they compare their results. The students then contrast the results from their apple investigations with what happens to teeth during the decay process. In addition, students discuss the processes of scientific inquiry and compare their investigation with how scientists find out about the world.


In this lesson, students will


After completing this activity, students will


Involving Students in Scientific Inquiry

Did You Know?
"From the earliest grades, students should experience science in a form that engages them in the active construction of ideas and explanations and enhances their opportunities to develop the abilities of doing science."
—National Research Council, National Science Education Standards1

Because students are naturally curious about the world around them, involving them in scientific inquiry is not difficult. Any time a student brings a rock, a bug, or a leaf to school, he or she is beginning the process of scientific inquiry. Your position as a teacher enables you to focus and refine their skills in scientific inquiry as they explore and make sense of the world around them.

In a classroom in which inquiry is taught and encouraged, it is important for students to develop both

students working in classExcept for "asking questions," which is usually the first step, there is no order to the processes of scientific inquiry. Contrary to popular thinking, scientists do not use "the scientific method," as students are often taught in school. Rather, scientists use all of the processes of inquiry as needed. Generally, scientists begin with a question, such as, How does that work? or What causes that to happen? To develop explanations of phenomena and events, they use their observations, experiments, knowledge, and logic.

As most teachers know, acquiring the ability to do science does not necessarily lead to an understanding of how science works in the world. Teachers need to weave together the abilities of science with the understandings of science. Students need to be encouraged to think of themselves as scientists and understand that, when they do science, they are using the very same processes that scientists use. If students are to understand how science works, they must compare what they are doing in their activities with what scientists might do in similar situations. The more they understand about the processes of scientific inquiry, the more they will understand the nature of science.

Using a Model

boy eating an appleIn this lesson, students use an apple as a model to investigate tooth decay. Like most models, the apple is not a perfect model for investigating tooth decay; an apple is not a tooth. However, you can use the apple model despite its limitations to help students transfer ideas about the apples to ideas about tooth decay.

Tooth decay (dental caries) is often recognized as a hole in the tooth, or a cavity. A cavity is actually the late stage of a dental infection that causes the tooth enamel to lose minerals. (See Lesson 4 for a detailed description of the process of tooth decay.)

The apple model's "hole in the apple" analogy is not entirely accurate because tooth decay begins under the surface of the enamel and not as a break or hole in the enamel. If the decay process continues unchecked, a cavity or hole eventually appears in the enamel. This, however, is a fine distinction and one that students don't need to make. It is sufficient for students to discuss tooth decay as "cavities" in teeth at this time.

The apple is a good model because it graphically illustrates decay spreading into the apple from a hole in its surface. From this observation, students make predictions about tooth decay that starts from actions on the surface of the teeth. Students don't need to understand details about how the decay process happens yet. Lessons 4 and 5 introduce students to the actual process of dental caries.

This lesson addresses many of the skills and abilities that students need to acquire to do and understand science. Students will ask questions, conduct an investigation, gather data, and communicate their results. Practice with scientific inquiry will help students understand the process of tooth decay and develop the skills needed to understand the world around them. You may want to review the National Science Education Standards1 to learn more details about the processes of scientific inquiry.


Activities that include the Web site
Activity Number Web Version
Activity 1 no
Activity 2 no
Take-home Activity no

Activity Number Master Number Number of Copies
Activity 1 Master 3.1, Apple Record Page 1 copy for each student
Activity 2 none none
Take-home Activity Master 3.2, Take-home Activity 2: So You Want to Be an Eggs-pert 1 copy for each student

Activities 1 and 2
For the class:
  • 1 apple, preferably Red Delicious
  • simple balance*
  • 2 or 3 thermometers**
  • sharp knife to cut apples (for teacher's use only)
  • assorted materials for student investigations, such as plastic containers with lids; plastic wrap or small plastic bags; aluminum foil
  • sheets of flip chart paper
  • markers
For each team of 2 or 3:
  • 1 apple, same type as control apple
  • 1 hand lens
  • 1 sharpened pencil
For each student:
  • 1 copy of Master 3.1, Apple Record Page
  • 1 pencil
  • crayons or markers
Take-home Activity
For each team (optional):
  • 1 egg
  • 1 plastic cup
  • white vinegar to cover egg in cup
  • plastic wrap to cover cup
For each student:
  • 1 copy of Master 3.2, Take-home Activity 2: So You Want to Be an Eggs-pert Scientist!
*Students can use the balance to compare the weight of their apple from day to day.
**Teams might want to measure the air temperature at the location of the experimental and control apples.


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