This is the teacher guide for this lesson. A student-focused guide to assist learners as they perform the activity is available.
Created by Olena Panasovska from Noun Project
Teacher Guide
Rusted Out and Blown Up
Experimenting with the effects of rust
How will hot and cold water move when they are placed together?
This resource was originally published in PhysicsQuest 2019: Heat.
How will hot and cold water move when they are placed together?
- Packets of vinegar (2)
- Steel wool
- Clear plastic bag
- Liquid crystal thermometers (2)
- Self inflating balloon
- Cup
- Paper towels
- Timer
Students make a prediction about what happens to a rusting object. Then, they get to experiment and observe what actually happens to objects when they rust. At the end of their experiment, they use their observations to compare to their predictions and solidify their thinking.
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 AreaHeat
- Educational topicThermodynamics
Every one of us has seen something rust. If asked to describe the rusting process, you might say something like, "metal left outside turns brownish and falls apart. Oxygen from the air combines with the metal and causes it to rust.” This is what happens, but there is a little more going on: the rusting reaction also gives off heat.
Chemical reactions can be either endothermic or exothermic. In an endothermic reaction, heat energy is absorbed by a material to make the reaction go, and the surrounding temperature drops. In an exothermic reaction, heat energy is released by a material, making it feel hot. If this reaction happens quickly, the heat energy released can be easily felt.
If a reaction occurs slowly, not enough heat energy is produced at one time to be felt. Rusting is usually a very slow reaction. Rusting Reaction 4Fe + 3O² è 2Fe²O³ 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 the end result is three oxygen atoms bonded with two iron atoms. This reaction is exothermic, so heat energy is released during the rusting process. However, there is too little to be felt by us since this reaction happens so slowly.
By making the rusting reaction happen very fast in this experiment, we make it possible to feel the heat energy. Steel is made of iron with some carbon atoms thrown in the mix. If you use steel wool at home, you know that it doesn’t usually rust, but that after using it for a long time, it will. Steel wool has a coating on it that makes it difficult for oxygen atoms to get to the iron to start the rusting process. Since steel wool is made of many fine strands of steel, there is a lot of surface area that can be exposed to air. If the coating wasn’t there, the steel wool would rust extremely quickly. In this experiment, students will speed up the rusting process of steel wool by using vinegar to remove the coating and then watch as the steel wool quickly rusts. Because it will rust so fast, it will be possible to feel the heat energy released from the reaction. Inside the self-inflating balloon are loose baking soda (NaHCO³) and a packet of vinegar (CH³COOH). When the packet is popped, a reaction begins between the baking soda and the vinegar and carbon dioxide (CO²) gas is released.
This reaction is most commonly seen in science project volcanoes. This experiment is usually too messy and uncontained for students to feel the temperature change indicating that it is an endothermic reaction. When sodium bicarbonate (baking soda) mixes with vinegar, the hydrogen atoms in the vinegar react with the baking soda. This creates an unstable chemical called carbonic acid (H²CO³) that quickly decomposes into carbon dioxide. Carbon dioxide gas creates the famous bubbles that come oozing out of volcanoes in science classrooms all over the country. This reaction absorbs energy for the atoms to rearrange during the reactions, and the temperature will decrease (making this an endothermic 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.
- 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.
- Endothermic: Meaning “inside heating,” this type of chemical reaction absorbs heat. It is the opposite of exothermic.
- Exothermic: Meaning “outside heating,” an exothermic reaction is one that releases energy. In this experiment, the energy is released in the form of heat.
- Kinetic Energy: Kinetic energy is the energy of motion. When things move they have kinetic energy.
Objective
Students will experiment with rusting objects to explain what happens.
Before the experiment
- Use the Ask and Discuss protocol
Predict three things that you might see when you watch something rust quickly.
- Use the Turn and Talk 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 clear plastic bag.
Stick the liquid crystal thermometer for measuring higher temperatures inside of the bag so that:
- You can see it through the bag.
- The thermometer touches where the steel wool will sit.
Pour both of the vinegar packets into a cup.
Stick the second liquid crystal thermometer for measuring cooler temperatures on the outside of the self-inflating balloon where the liquid will collect.
Make a chart to collect your data in the Collecting Data section on page 36.
During the experiment
Collecting data
Make sure students are put into intentional groups. See above.
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 answer questions that help them understand what rust does to objects.
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
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.
- Consider using white boards so students have time to work through their ideas and brainstorms 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. Look for *** below to find suggested places to add.
Conclusion
- Post the conclusion question
Look back at your predictions. How does what you saw compare with what you thought you would see?
- Use the Share-trade protocol
Use the Share-Trade protocol to have students share and refine their thinking.
- Each student writes their individual thoughts.
- 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, even if they don’t agree with those ideas. This isn’t a time for them to critique their partners’ ideas.
- Students form partnerships three or four times so they see and explain multiple ideas.
- Students return to their seats and write a final explanation or idea.
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?
Credits
Coordination, Research, Text, and Editorial Review Jon Anderson, Isabel Bishop, Randie Hovatter, Jamie Liu, Leah Poffenberger, James Roche, Natalie Ruiz, Laurie Tangren, Rose Villatoro, David Voss
Graphic Design and Production Meghan White
Illustration of Experiment Guides Isabel Bishop
Illustration of Dr. Chien-Shiung Wu Annamaria Ward
Updated in 2023 by Sierra Crandell, M.Ed. partially funded by Eucalyptus Foundation
Extension by Jenna Tempkin with Society of Physics Students (SPS)