This is the teacher guide for this lesson. A student-focused guide to assist learners as they perform the activity is available.
Teacher Guide
Rusted Out
An experiment to explore rusting metals.
What happens when an object rusts?
This resource was originally published in PhysicsQuest 2011: Spectra Heats Up!
What happens when an object rusts?
- Packets of vinegar
- Steel wool
- Clear plastic bag
- Liquid crystal thermometer
- Cup
- Paper towels
- Stopwatch or watch with a second hand
Students start by discussing what they already know or have observed about objects that rust. They observe and collect data on steel wool and the effects of different variables. Then, they compare their predictions to their data and describe what happens to objects when they rust.
Suggested STEP UP Everyday Actions to incorporate into activity
- When pairing students, try to have male/female partners and invite female students to share their ideas first
- As you put students into groups, consider having female or minority students take the leadership role.
Take note of female participation. If they seem to be taking direction and following along, elevate their voice by asking them a question about their experiment.
- Total time45 - 60 Minutes
- Education levelGrades 5 - 9
- Content AreaThermodynamics
- Educational topicThermodynamics
Everyone has seen something rust. If asked to describe the rusting process we would all say something like “metal left out in air turns brownish and falls apart. Air is combining with the metal and turning it into rust.” This is exactly what happens but there is a little more going on. In this experiment we are making something rust extremely quickly and because of that we can learn even more about the process.
Chemical reactions can be either endothermic or exothermic. In an endothermic reaction heat from the surrounding material is used to make the reaction go and the temperature drops. In an exothermic reaction energy is released during the reaction. If this reaction happens quickly the heat released can be easily felt. But if it is a slowly occurring reaction, not enough heat is produced at one time to be felt. Rusting is usually a very slow reaction. Rust is formed when three oxygen atoms bind with two iron atoms.
There are a lot of steps in between and the reaction needs water to help it out, but in the end, there are three oxygen atoms with iron atoms. This reaction is exothermic so every time it happens, a little bit of heat is released. If the reaction happens very slowly, only a very tiny amount of heat is released each time the reaction occurs, too little heat to be felt by us. This is why your neighbor’s yard-car doesn’t feel hot as it slowly rusts up on its blocks. But, if there is a way to make the reaction happen very, very fast, it is easy to feel the heat.
Steel is made of iron with some carbon atoms thrown in the mix. If you use steel wool around the house you know that it doesn’t usually rust quickly, but that it will after using it for a long time. Steel wool has a coating on it that makes it very difficult for oxygen atoms to get to the iron in the steel to bind with them. But, because steel wool is made of a lot of fine strands of steel there is a lot of surface area exposed to air and if the coating wasn’t there, the wool would rust extremely quickly.
That is what we are doing in this experiment, we remove the coating with vinegar and watch the wool rust. Because it rusts so fast, it is possible to feel the heat released from the reaction.
Key terms
These are the key terms that students should know by the END of the two lessons. They do not need to be front loaded. In fact, studies show that presenting key terms to students before the lesson may not be as effective as having students observe and witness the phenomenon the key terms illustrate beforehand and learn the formalized words afterwards. For this reason, we recommend allowing students to grapple with the experiments without knowing these words and then exposing them to the formalized definitions afterwards in the context of what they learned.
However, if these words are helpful for students on an IEP, ELL students, or anyone else that may need more support, please use at your discretion.
- Exothermic: Meaning “outside hearing,” exothermic reaction is one that releases energy. In this experiment the energy is released in the form of heat.
- Chemical reaction: In a chemical reaction molecules interact to create a new substance. They can combine, separate or change the way they are bound together.
- Kinetic Energy: energy of motion. When things move they have kinetic energy.
Objective
I can observe and collect data on the changes that happen when something rusts.
Before the experiment
- Ask & Discuss
What is something that you have owned or seen that has rusted? What are some things you think could have made it rust faster or slower?
- Snowball Protocol
- Pair students up
- Give them a minute to think quietly
- Give students 2 minutes to discuss their thinking
- Have students record their answers or share out to the whole group
Setting Up
Open the zip lock bag
Stick the liquid crystal thermometer to the inside of the bag so that you can see it through the bag. (Figure 1)
Figure 1Pour all the vinegar packets into a cup.
During the experiment
Collecting data
Make sure students are put into intentional groups.
Students will complete the experiment using the Student Guide where we have outlined the experiment for students and along the way, they record results and answer questions.
Analyzing data
In the student guide, they will record observations of the steel wool.
Continue to listen in on each group’s discussion, answer as few questions as possible. Even if a group is off a little, they will have a chance to work out these stuck points later.
Teacher tip
A great way to start any physics-related unit is with the STEP UP Careers in Physics lesson. This lesson covers careers one can do with a physics degree, particularly those that help solve societal problems. It helps students assess their personal values in relation to a career in physics, examine profiles of professionals with physics degrees, and envision themselves in a physics career.
Suggested STEP UP Everyday Actions to incorporate into the activity:
- When pairing students, try to have male/female partners and invite female students to share their ideas first.
- As you put students into groups, consider having females or students from underrepresented backgrounds take the leadership role.
- Take note of female participation. If they seem to be only receiving direction and following along, elevate their voice by asking them a question about their experiment.
Consider using whiteboards so students have time to work through their ideas and brainstorm before saying them out loud.
As students experiment, roam around the room to listen in on discussion and notice experiment techniques. If needed, stop the class and call over to a certain group that has hit on an important concept.
Consider using the RIP protocol (Research, Instruct, Plan) for lab group visits and conferring.
Consider culturally responsive tools and strategies and/or open-ended reflection questions to help push student thinking, evidence tracking, and connections to their lives.
Conclusion
Share-Trade protocol to have students share and refine their thinking around the question: How does what you saw compare with what you thought you would see?
- Each student writes their individual thoughts using the stem “First I thought_______________. Now I know_________________.”
- Students stand up with their ideas on paper and move around the room.
- Each student finds someone they don’t know very well and forms a partnership with them. To form a partnership, students must high five.
- With their partners, students share their ideas and trade papers.
- Each student is now responsible for sharing the ideas of the person they just spoke with.
- Students form partnerships three or four times so they see and share multiple ideas.
- Students return to their seats and write a final explanation or idea to answer the question, “What happens when something rusts?”
After students have had a chance to discuss key ideas from the lesson and complete their student guides, you can now clarify and give concise definitions to the forces they experimented with.
- Real world connections -
- Compare two different climates, which one has a higher chance of things rusting? Try to find evidence through a google search of people detailing things that rust and the time it takes in your two chosen climates.
- Suggestions for drawing, illustrating, presenting content in creative ways
- Draw the process of an object rusting.
- Engineering and design challenges connected to the content
- How could you prevent something from rusting?
- MS-PS4-3Integrate qualitative scientific and technical information to support the claim that digitized signals are a more reliable way to encode and transmit information than analog signals.
- MS-PS4-1Use mathematical representations to describe a simple model for waves that includes how the amplitude of a wave is related to the energy in a wave.
Credits
Written by Rebecca Thompson
Illustrations by Kerry G. Johnson
Activity illustrations by Nancy Bennett-Karasik
Updated in 2023 by Sierra Crandell, M.Ed. partially funded by Eucalyptus Foundation
Extension by Jenna Tempkin with Society of Physics Students (SPS)