Planetary Crusts Unit: Ice Balloon Demonstration

 
Lesson History
School

Franklin Middle School (please give me feedback) (please take a look at the big picture)

Please note that this demonstration is currently being developed. I do not yet know how much give the ice will have and how best to demonstrate that give to the class. Further, I do not know if I can pass them around or let groups have one or if I need to do it as a demonstration up front with some sort of camera.

Class

8th Grade Science

Date(s)

est. March 2004

Learning Objective
 

This demonstration will get students thinking about how one can know the state of matter inside (or under, depending on your point of view (whole world vs. local)) the crust of an astronomical body.

National Standard(s)

PRIMARY STANDARD (more here)

Sci.I.1 All students will ask questions that help them learn about the world; design and conduct investigations using appropriate methodology and technology; learn from books and other sources of information; communicate their findings using appropriate technology; and reconstruct previously learned knowledge.

Sci.V.1 All students will describe the earth's surface; describe and explain how the earth's features change over time; and analyze effects of technology on the earth's surface and resources.

Throughlines
  1. How do structures and processes relate to energy and its use?
  2. How do differences in scale affect processes with which we are familiar?
Driving Question
  1. What is a crust?
  2. How are crusts related at different scales?
  3. What kind of energy does a crust contain?
  4. How is the crust of the Earth and other planetary bodies related to the crusts of things we use every day?
 
as Related to Objective

 

  1. Students will see a practical example of a planetary crust.
  2. Students will consider a crust on the small scale of a balloon full of ice.
  3. Students will see how strong a crust is which is containing a liquid. This may give some insight into the violence of volcanic eruptions.  (This may not be as strongly related to the driving questions as other lessons are.)
  4. Ice cubes which are not frozen solid also display these crusts.
 
 
Activity
 
Preparation
  1. Buy water balloons (15 minutes).
  2. Fill water balloons (5 minutes).
  3. Allow water balloons to almost freeze from the outside in (several hours).
Materials Needed
Resource What is it? File(s)

Water Balloons

Fill water balloons with water and leave them out in a snowbank to freeze. You will want to pack snow all around them to make sure they freeze evenly. Alternatively, you may want to turn them as they are freezing.

none

Activity Time

Depends on how in depth the discussion goes, and what questions the students have. I'm guessing one 50-minute class period, but if it's shorter then we could move on to the lesson on the Science News article the same day and that would be good.

Instructional Strategies (Science Instruction pg. 244)
This is primarily a demonstration of the properties of solid spheres with molten interiors. It is introduced by a discussion of the Earth's crust (including glaciers) and molten interior, and is followed by a discussion of planetary crusts and dead planets and leads to a recitation on a Science News article.
Instructional Sequence
  1. (5-10 min) Discuss water (glaciation, how water from the ocean snows over ice to form glaciers which melt back to the ocean, how this gouges out great lakes) as part of the Earth's crust (tectonic plates, Earth's crust, molten core, magma).  During every portion of the discussion, feedback will be given to the students informally.
  2. (while talking) Take out the frozen water balloon and start to unwrap it.
  3. (10-15 min) Talk about ice as rock and how certain moons and all comets have a solid surface of (dirty) water ice. This solid ball in my hand could be solidifying rock (like Mars) or ice (like Europa).
  4. (10-20 min) Ask the class how we might be able to tell a completely solid planet from a partially molten one.  The class will brainstorm and each member will make a concept map of the brainstorm in their notes.  Perhaps a student or students come up with the method used in the article we read.
  5. (5 min) (I originally got the idea for this lab from observing how ice cubes freeze from the outside in. The problem is, that when I try to get them out of the tray, they break. I therefore decided using balloons to hold the water might work better. I have not yet gotten a working model for this and am waiting for a snowfall to see how they freeze.)
    At this point in the lesson, I want to show the flexibility of ice balloon in some manner to be determined. I need a good snowfall to test this demonstration and see how best it will work, but I have several ideas:
    • Give them to the students: ideally, it will be very easy to make an ice balloon that deforms readily without breaking too easily. If this is true, I can give every group an ice balloon, maybe even with the rubber removed, and they will easily see the deformation for themselves.
    • Pass one around: it may be that the ice balloons are difficult to make properly, so that it is impractical to make one for each group. If they are strong enough, and deform easily enough, I could pass one around. If students break it, it could become a teaching moment for how the Earth breaks in volcanoes and earthquakes.
    • Demonstrate up front: perhaps the balloons will be particularly fragile, such that I will not be able to pass them around (or I can tell a particular class is too rowdy). In this case they may be able to gather round and watch as I deform it carefully.
    • Use an aid: it could be that the deformation is too small to measure (as water is an "incompressible" liquid), and that some aid (such as the overhead) would be necessary to magnify the effect. Alternatively, another liquid could be sought to fill the balloons and we return to the first idea for demonstration and try all the ideas out again.
  6. (5-10 min) Hopefully there will be some give in the actual sphere that the students can feel (probably not though). Pass the sphere around.  As we continue the discussion, we will also talk about the reasons why each method would or would not work. (I have not yet done this. I'm waiting for a good snow fall.)
  7. (transition) Lead into the discussion on a molten Mars where they will apply their knowledge.  The article will use compressing the planet as a means for measuring the liquidity of Mars' interior, but any valid methods will be accepted.
Cautions

Ice balloons will be hard and students must be warned not to throw them.

Assessment

During discussion there will be informal assessment of prior and post activity knowledge. I will be looking for prior knowledge on the process of glaciation in particular and on the water cycle in general as well as knowledge about the structure of the Earth. (This is connected to knowledge they gained before the lesson, and what they need to know afterward. It depends on the final sequencing which has not yet been determined.) Depending on where this lesson falls in the sequence of the unit, this will either be a brief review for the students or it will be brief introduction. I'm not looking for take home knowledge here, but if I can stress these processes over and over, students should eventually get it.

During the demonstration I am looking for questions and comments which show critical thinking about how we could tell the difference. (Is there give? Can you stick your finger through (volcano)?)

(Everything gets so tied together.  The real key assessment for this lesson plan is actually embedded in the next one.  The students will apply what they have learned to inform their understanding of the article showing that Mars has a molten core based on this technique of observing the squeezing of the crust.) (I'm more interested in them learning how to think like a scientist than in the particular solution, though it would be good for them to know that too.)

Rationale
  1. Objective -- It is worthwhile knowing how modern science can decide that Mars still has a molten core. This demonstration takes a modern marvel and makes it understandable on an everyday level. This shows science in the real world as it is practiced.
  2. Sequence -- The sequence is set up to engage students starting with their previous knowledge and leading them through a discussion to make the article that follows seem interesting to them.
  3. Assessment -- Informal assessment makes sense in this lesson as I am just starting to get students to think about these issues. The real assessment comes in the next lesson when they show they understood the concepts here by understanding the Science News article.
  4. Parts & Whole -- A discussion without demonstration can be boring. A demonstration without discussion is amusing, but without lasting understanding. A discussion with demonstration can leave a lasting construct in a child's mind which they can keep and use in the future to understand new phenomena.
  5. Technique -- This lesson is an example of scaffolding the scientific approach to thinking about problems as I am giving my students a way to understand the article which follows.
How it Went/Lessons Learned

I haven't tried this lesson in the classroom yet.  The refrigerator in my dorm doesn’t cool things evenly enough to do this.

 
Unit: Ice Balloons, SN: Molten Core

This is the demonstration lesson plan for Education 422: "Teaching of Science in the Secondary School (MAC)."

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Daniel D. Slosberg | salinay@umich.edu
December 1, 2003