Testing Material Properties

Background Information for Teachers

We encounter hundreds of different objects every day and many of them are made from different materials. Plastic, metal, ceramics, or wood are just a few materials of which objects can be made. Why is it that every object is not made from the same material? It is because different materials have different properties. Such properties include mechanical properties like flexibility, hardness, or durability; chemical properties like corrosion resistance or pH; optical properties like color or transmittance; and thermal properties like boiling point or flammability. There are many more material properties than the ones mentioned here. You can find a more extensive list in the Additional Background section.

Testing and measuring the characteristic properties of a specific material is a significant aspect of material science (Figure 1). To characterize a specific material, it is usually subjected to a range of tests. Each of these tests usually measures a different property. For example, bending and stretching a material tells us about how flexible a material is, and shining a light onto a material tells us about its optical properties. The collective properties of a material often determine what the material can be used for. Every manufactured product needs to be made of materials that are suitable for its particular application. As there are so many different materials to choose from, testing of materials can help narrow down the choices to the most appropriate selection for a specific product. For example, an umbrella needs to be made of water-resistant materials, and glasses need to be made out of transparent materials.

Image Credit: Wikimedia user Skatesandy / Creative Commons Attribution-Share Alike 4.0 International Image Credit: Wikimedia user Cjp24 / Creative Commons Attribution ShareAlike 3.0 Unported
Figure 1. Left: Testing the tensile strength measures the force required to break a material. Right: The three-point bend is used to determine the flexibility of a material and measures the force required to bend the material under specific loading conditions.

The development of new materials is another big research area in material science. Researchers not only try to improve existing materials to make them better, but they also create completely new materials with very specific or novel properties to push the boundaries of what conventional materials can do. Semiconductors, nanotechnology, carbon fiber, and plastic are just some of the materials that have been made by humans for very specific purposes.

In this lesson plan, students will conduct their own range of material tests, which include the assessment of mechanical, chemical, and optical properties. While testing different materials, they will realize that each material has its own characteristic properties. Based on their results, students will classify different materials according to their observed properties and discuss for what purpose different materials could be used.

Additional Background Links

• List of materials properties, Wikipedia
• The top ten advances in materials science, Science Direct
• TWI - an introduction to mechanical testing techniques, TWI Ltd on YouTube

Prep Work (15 minutes)

1. Gather enough materials for each student group to test. Preferably, each group will test a different set of materials.
2. For each group; set up a testing station with the bowl of water, the medicine dropper, the coin, and the flashlight. You may also want to provide paper towels for any water spills.
3. Print out one copy of the Student Worksheet for each student. You can save time during the activity by filling in the material column in the Student Worksheet before class, based on the materials you have selected for testing.

Engage (20 minutes)

1. Show students the two same-sized balls made of different materials. Pass them from one student to another so they can feel the balls and look at them more closely. Then ask:

   What do you notice when looking at these two balls?

   How are the two balls similar or different?

   Do you think there is something that I can do with one ball, but not with the other? Why?

   Collect students' responses. Elicit responses that mention how the two balls look different or how they feel different.

2. Continue to ask:

   Why do you think the two balls look or feel different?

   Again, listen to students' ideas. Prompt them to think about what the two balls are made of. Students should realize that each is made from a different material.

3. Explain to students that there are many different materials that things can be made of. Challenge them to come up with different materials they know.

   Can you name a material that is hard?

   Can you name a material that you can see through?

   Can you name a material that you can bend?

   Record children's responses for each category. Highlight any of the students' responses that meet multiple categories. For example, glass is hard and you can see through it.

4. Point out to students that a material can have different properties. A material property is a physical property that can be observed or measured. Ask students if they can name some material properties.

   What are some material properties that you know?

   Collect students' replies. They might mention the color of a material, or the softness/hardness. If students struggle, give them some examples of material properties. You can find an extensive list in the Additional Background section.

5. Explain to students that each material can have many different properties. At the same time, different materials can share the same material properties. Discuss:

   How can we tell what material has which properties?

   How could we find out which materials have the same or different properties?

   Have children share their ideas. Focus on responses that mention that you can test and compare materials to see what properties they have.

Explore (40 minutes)

1. Show children all the materials on the table. Let children describe the materials they see. Ask them to name one specific property of each of the materials. Then tell them that today they will do a series of tests to find out what other properties these materials have.
   Divide your class into groups of 3 students and assign each group one of the prepared test stations. Have each group select 2-3 materials from the table that they would like to test.
2. Explain that each group will do 5 different tests with their selected materials. With the help of 1 or 2 students, briefly demonstrate how to conduct each test.
   1. Flexibility: Students try to deform a material by bending it with their hands as hard as they can. Does the material bend, break, or stay the same?
   2. Hardness: Students scratch the material with a coin as hard as they can. Does the coin leave scratches on the material or not?
   3. Transparency: Students shine a flashlight onto a wall and place the material into the beam of light. They observe if light passes through the material or if the material casts a shadow. Does light pass through the material or does the material cast a shadow? Remind students not to shine the flashlight into each other's eyes.
   4. Water resistance: Students put a drop of water on the material with the medicine dropper/pipette. Does the material absorb the water (does it sink into the material)?
   5. Behavior in water: Students place the material in a bowl of water. Does the material sink or float?
3. Review the Student Worksheet with your students and point out what they should record in each column of the table.
4. Once each group is ready, let students carry out their material testing independently. During testing, check in with each group regularly to answer questions and help with testing where necessary. Make sure every student participates in the testing. Each student within a group can conduct the test or they can take turns in testing the different properties. It might also be helpful to provide paper towels in case of water spills.
5. While they are testing, have students discuss within each group:

   What do we observe with each of the materials in each test?

   How are our chosen materials similar or different from each other?

   Which properties do our materials share?

   Were any of the results surprising?

Reflect (30 minutes)

1. Once all student groups have completed their testing, come back together as a class and collect all their materials on one table or at a place where everyone can see them. Have students share their observations with the rest of the class. Ask them to present the properties of each of their selected materials and have them address the following questions.

   What did you observe when you tried to bend a material?

   What did you observe when you tried to scratch a material?

   What did you observe when you placed a material in the bowl of water?

   What did you observe when you dropped water on the material?

   What did you observe when you shone light onto the material?

   While one group is presenting their results, guide the other students to enter each of the material's test results into their Student Worksheet.

2. After all groups have finished their presentation, look at the data sheet together. Have students classify or group all the materials on the table based on their properties.

   When looking at your results, what materials have very similar properties?

   What materials on your list are very different from each other?

   If you had to group (or classify) all these materials based on their properties, how would you do that?

   Have students share their ideas. Then ask students to group/classify all the materials on the table. Have students explain, with evidence, why they sorted the materials a certain way. Point out that classification means to group objects based on shared qualities or properties. Encourage students to place all the objects into separate piles based on their properties. For example, they could place all transparent materials in one pile and the opaque ones in another pile. Note that they can group the objects in different ways depending on what material property they are using as classification criteria.

3. Point out that in addition to the tests they have conducted, there are many more tests to assess even more material properties. Point out that material testing is an important part of material science. In fact, there are whole laboratories designed just to do material testing. Discuss with your students:

   Why do you think material testing is important?

   Why would we want to know the properties of a material?

   Listen to students' replies. Guide them to conclude that we have to know the specific properties of a material if we want to use it for a specific product. For example, if I want to build a bridge, I need a material that is very strong, durable, and that is weather-resistant. If a material fails, it can potentially have significant impacts on the product or its user.

4. At the end of the lesson, have students summarize what they have learned by asking them to explain why there are so many different objects with so many different materials out there. Let them pick a random object from their surroundings and encourage them to explain, with reasoning, why they think this object was made of that particular material.

Make Career Connections

Discussing or reading about these careers can help students make important connections between the in-class lesson and STEM job opportunities in the real world.

Materials Scientist and Engineer

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Career Profile

Material scientists study all aspects of materials to develop new products or to improve existing ones, such as airplane wings, computer chips, cars, and bridges. They work with ceramics, plastics, metals, and even create new materials that can be used to make products stronger and better. To find out if their new materials have the properties they need, material scientists spend a lot of time in laboratories performing material testing. Read more

Lesson Plan Variations

• You can play the "I spy with my little eye" game with your students. Place all the materials back on the table where every student can see them. Have one student secretly select one object from the table and describe it by describing its properties. Each hint has to be based on a specific property of the material, especially the ones that they just tested, such as "I spy with my little eye something that floats on water and is water-resistant."
• Let students investigate additional materials using the same 5 tests.
• Have students choose one of the tested materials and discuss a new test for that material.
• Give students a design problem. They need to make a product for a specific purpose and application. This means the object has to have certain properties. Students have to discuss and find out which materials would be best suited to make this product. Have students explain the reasoning for their material choice. They could, for example, build a bridge out of different materials, as described in Science Buddies' Paper Bridge Materials Challenge lesson plan.