It Egg-sploded!
A guided inquiry into matter changes for primary grades.
by Destiny Warner
This lesson follows Iowa Core Essential Concepts and Skills for K-2: Understand and apply knowledge of characteristics of liquids and solids. Materials can exist in different states – solid, liquid, and gas. Some common materials, such as water, can be changed from one state to another by heating or cooling.
Introduction:
The discussion of matter and matter change is common in science classrooms from an early age. A basic understanding of matter is an important foundation for later learning so why limit instruction to abstract text and vocabulary instruction?
Constructivist learning theory teaches us that students do not learn from rote memorization and lecture only. John Dewey stated that, "If knowledge comes from the impressions made upon us by natural objects, it is impossible to procure knowledge without the use of objects which impress the mind," (Dewey, 2009). Learning must be concrete. We must use personal experiences and make contact with the world if we are to learn from it.
In this lesson the teacher guides students using questioning strategies to assess students’ prior knowledge as well as move forward within the experiment. For student conceptions to change, change must come from within the student via personal observation and careful consideration.
Previously Covered Content:
First, I assessed their knowledge of matter after a primary lecture but before experimenting to determine what misconceptions they might have (Figure 1). Using their answers I decided to focus on one major misconception:
- If different objects are heated/cooled for the same amount of time and at the same temperature, those objects will change in the same way no matter their material.
Figure 1: Pre-Assessment Questions
What do you know about matter (stuff) and how it changes?
What would happen if we put an object like carrots, eggs, water, or soap into a freezer?
Would each item change in the same way? Why?
What would happen if we heated an object like carrots, eggs, water, or soap in a microwave?
Would each item change in the same way? Why?
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Investigation:
Figure 2: Materials Needed Per Group
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Please note: In this experiment it is important to use Ivory brand soap because other brands will melt and create a great deal of smoke when heated in a microwave. Also, it is wise to test experiments at home before they are conducted with students, but mistakes can make for authentic learning opportunities.
To prepare for this lesson I placed a carrot, egg, piece of soap, and water in a freezer 24 hours in advance. I also prepared a list of questions to have available if I struggled during group discussion.
To start with I bring out a carrot and have the students examine it. “Describe the carrot.” Students will probably say some variation of, “Hard,” “Orange,” “A little bendy. “ Encourage students to think about previous discussion on matter. “Why is the carrot a solid? Why is there liquid inside this solid?” When questioning it is important to make appropriate use of Wait Time 1 to prompt student thinking and expression of thought processes. With second graders, most are still eager to answer questions so a teacher shouldn’t have to wait more then 2-4 seconds. In my experiences with this experiment, I didn’t have to ask many questions because the students asked them first. I was often quiet and able to let them do the talking. “It stinks!” “It’s squishy.” “Let me touch it!” While experimenting, most young primary students will just shout out whatever they saw that was interesting to them. Encourage this. Some students will need more prompting, but that can also be done by asking, “Everyone, what do think about what Jennifer said? What else might happen?” Science is collaborative by nature so it is important to model that in your teaching.
“What would happen if we put a carrot in a freezer overnight?” Some common responses are, “It would freeze,” “Get harder,” “Get covered in ice.”
“How would we test that?” Most, or at least one, students will come up with the idea of placing the carrot in the freezer overnight. Once that happens, then bring out the carrot from the freezer and ask, “Describe the carrot now.” Most students will probably just say, “It froze,” but push for further information. “What do you mean by ‘it froze?”
“What do you think would happen if we heated a carrot?” “ How would we test that?” Talk with the students to work out how long a carrot should be heated in a microwave (one minute is plenty) and let them observe the process through the door. Afterwards, remove the carrot carefully by holding on to the edges of the napkin or using a hot -pad if you placed the carrot on a plate since the carrot and plate will be hot. Then push the students to describe how it changed.
“What is that coming off of the carrot?” Most students will say it is smoke but some might know that it is steam. At this point it is a good lead to go back to the first carrot and break it in half to show the slightly wet insides. “What happens if water gets really hot?” Most will say that it “boils,” but not know what the steam is. Measure out a small amount of water in a clear cup and mark on a line where the water level is. “What do you think will happen if we heat the water in the microwave?” “How long should we heat the water?” In this it is okay to nudge the students toward the same amount of time that you heated the carrot so that the same thing is done to each object. “How can we make sure that we are being consistent about cooking time?” “Why should we be consistent?”
Students (and scientists!) are curious by nature so once cool enough let the students poke and bend each carrot. Break each carrot in half so they can compare the insides. Direct the students to record (write or draw) their observations on the three carrots in their notebooks.
Once done with the carrots, bring out an egg. Let students examine and touch it. Encourage them to talk. Ask what the inside of a raw egg is like and then crack open the egg over a sink or bowl so that they can confirm or disprove those thoughts.
“What do you think will happen if we freeze a raw egg? Write down your prediction in your journals. Feel free to write, draw a picture, and use labels like on a diagram.” Retrieve the frozen egg from the freezer. Most students will make their own comments without prompting, “It froze!” “It cracked!” “It’s cold.” After students touch the egg, ask, “What do you think the inside of the egg is like now?” Each time I asked a student would suggest breaking it open. Attempt to do so. Bang it on the side of the sink, use a butter knife, etc. Try to break it. If frozen overnight it will not break. “What state is the egg in now?” “How are the frozen egg and the frozen carrot the same? Different?” “What will happen if we heat an egg in the microwave?” Direct students to write their predictions in their journals.
When talking with students it is important to use language appropriate for second grade students. This age is not the time to be talking about physical and chemical changes. Instead, focus on how each object changes between solid, liquid, and gas because of changes in temperature. If you find yourself wondering if your class is ready for a science concept I recommend that you refer to the Atlas of Science Literacy Vol. 1 and 2.
Continue with the experiment and microwave the egg for the length of time the students recommend. It will crack open in the microwave, pour out of the shell and cook to a fluffy solid. Have students compare with the previously heated items. “How does heating this egg after heating the carrot change your thinking about what happens when stuff gets hot?” “How can we compare what we think now to what we thought earlier?”
Finish this activity by getting out the Ivory soap. Discuss the soap, its appearance and state of matter. Have the students write in their journals their predictions of what would happen one chunk of soap was placed in the freezer and another was heated. Push them to converse with each-other about what they think will happen. When frozen, the Ivory soap will barely change. It gets cold, but no harder. Pass it around and let them make their own observations though.
“What should we do next?” Students will direct you to microwave the soap. “How long?” Most will say “One minute!” or however long you heated the previous items. “Why do you say one minute?” Follow their directions and step back so they can watch through the door. The Ivory soap will expand to many times its original size. It’s very light, fluffy, and can be squished. Encourage discussion and exploration. Have them journal what really happened in their science journals.
At the end of this lesson ask again, “If we heat or freeze different objects for the same amount of time, why don’t the same things happen to them?” Push them to talk to each-other and assess how their knowledge has changed. Collaboration is a key part of science research and it is important to foster this important aspect with students and their peers. “How did your ideas about solids, liquids, and gases change?” Some students may try to say that their thinking didn’t change. When that happens draw their attention to what they wrote in their journals before and after the experiment. “It’s okay for ideas to change. Scientists learn and add to or change their thinking every day. How does that help them to be better scientists?”
“How did working in a group change how you thought?” “It was weird.” “I didn’t like his answers.” “I like what she said because I thought it too.” “It made me feel better to know we were both wrong.” “I like that we all were wrong and right about different things.”
“How do you think these types of things make scientists better at their jobs?” “It makes it so they can get lots of ideas and have lots of friends to help them work, even if they don’t like them so much.” “Maybe they can get more stuff done or get more money because there are more hands.”
Conclusion:
This activity is a useful experiment in demonstrating that "things can be done to materials to change their properties, but not all materials respond the same way to what is done to them. 4D/2," (Atlas of science literacy, 2001). This activity is an implicit and explicit way to demonstrate the social and collaborative nature of science while teaching content and adhering to state standards.
Bibliography:
Dewey, J. (2009). Democracy and education: An introduction to the philosophy of education. New York: WLC Books.
(2001). Atlas of science literacy. (Vol. 1). Aaas Project 2061
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