Download Big Ideas

Iron Filings in Fluid
Big Ideas
TEKS
grades 5 - 8
Properties of
Matter
5.7-A
Systems
5.5
Critical
Thinking
x.3-C
Force and
Motion
6.6-A,
Atomic
Structure
8.8
Natural
World
6.13-A,
Content Relationship
A gas - if it contains charged particles (ions) - can have magnetic and electric
properties. It will line up, like iron filings do, in a magnetic field.
The fluid, filings, and magnetic field are part of a system
Sunspots are manifestations of the interaction between magnetic fields and the
photosphere.
Model limitations: Sun's photosphere is very hot
There are no iron filings in the Sun. They represent atoms in the photosphere.
The bar magnet represents a local magnetic field in the Sun due to the motion of
charged gas in the photosphere makes the magnetic field
Iron filings move in response to the forces of the magnetic field until they reach a state
of equilibrium (sum of forces = 0; energy in = energy out).
The iron atom contains a positively charged nucleus surrounded by a negatively
charged cloud of electrons. Each proton and electron has the same unit of charge:
positive for the proton, negative for the electron.
Ferromagnetism is the name of a curious behavior of iron, nickel, cobalt, and other
metals. Tiny regions (mm size) inside chunks of iron can align their magnetic domains,
like lining up tiny magnets, to make one big magnetic field. Normally, these domains
are not aligned, so when you add up all the tiny magnets, the field sums to zero. Copper
does not have this property, so does not respond to a magnetic field. Steel (made of
iron and carbon) will respond to a magnetic field.
Further explanation gets into electron spin – not appropriate for 8th grade!
The Sun generates its own magnetic field. Sometimes strong fields interact with small
areas of the photosphere, making sunspots or spouting prominences.
Lava Lamp
Big Ideas
TEKS
grades 5 – 8
Content Relationship
As the temperature of the goo-cell rises, its density decreases, volume increases, but its
mass remains constant – it floats. The surrounding fluid has different properties, so it
will respond differently to changes in temperature.
The system of the lava lamp is like the Sun's convective layer.
Systems
5.5
The inner layers of the Sun are much hotter than the lava lamp bulb.
Critical
Cells in the Sun are large – Earth size – and extend thousands of kilometers below the
x.3-C
Thinking
photosphere
Why does the goo-cell rise and fall?
The process of convection requires a gravitational field. The idea of floating means
there is some force balance: the force of gravity (weight) balanced by some force
pushing you (or a goo-cell) back up. When you swim and float in a pool of water, some
force has to balance your weight. That force is called buoyancy, but it's really just the
weight of the fluid (water or air) that your body displaces when you jump in the pool.
When you get in a pool, you displace a volume of water – the pool level rises. You
have done work against gravity, so the pool water pushes back on you with a force
Force and
6.6-A,
equal to the mass of water you displaced time the acceleration of gravity (F=mg).
Motion
When this buoyant force equals your weight, you float.
When you put on a pair of "floaties" in the pool, your body+floaties can displace more
water. You and the floaties will displace a volume of water until the water volume
weight = your weight (plus the floaties).
As the goo-cell temperature rises, the goo-cell expands: it gets bigger and displaces
more fluid, but its mass remains constant, so its weight remains constant. The fluid
pushes back on the goo-cell with a force greater than the goo-cell's weight, so it floats.
Characteristics of the Sun: Granules in the Sun's photosphere transport energy from the
Natural
convective zone out into space. This is the light we see. The lava lamp is a cross
6.13-A,
World
section of a granule. Granules are about the size of the Earth (some bigger or smaller).
Note: Great physics reference - Hyperphysics (http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html)
Properties of
Matter
1
5.7-C,
21 Oct 2005
Texas Essential Knowledge and Skills
Grade
5-8
5
6
8
TAKS
Objective
TEKS
x.3 The student uses critical thinking and scientific problem solving to make informed decisions.
(A) analyze, review, and critique scientific explanations, including hypotheses and theories, as to their
strengths and weaknesses using scientific evidence and information;
(B) draw inferences based on information related to promotional materials for products and services;
(C) represent the natural world using models and identify their limitations;
(D) evaluate the impact of research on scientific thought, society, and the environment; and
(E) connect Grade x science concepts with the history of science and contributions of scientists.
5.5 The student knows that a system is a collection of cycles, structures, and processes that interact.
(A) describe some cycles, structures, and processes that are found in a simple system; and
(B) describe some interactions that occur in a simple system.
5.7 The student knows that matter has physical properties. The student is expected to:
(A) classify matter based on its physical properties including magnetism, physical state, and the ability to
conduct or insulate heat, electricity, and sound;
(B) demonstrate that some mixtures maintain the physical properties of their ingredients;
(C) identify changes that can occur in the physical properties of the ingredients of solutions such as
dissolving sugar in water; and
(D) observe and measure characteristic properties of substances that remain constant such as boiling
points and melting points.
6.6 The student knows that there is a relationship between force and motion.
(A) identify and describe the changes in position, direction of motion, and speed of an object when acted
upon by force;
(B) demonstrate that changes in motion can be measured and graphically represented; and
(C) identify forces that shape features of the Earth including uplifting, movement of water, and volcanic
activity.
6.13 The student knows components of our solar system. The student is expected to:
(A) identify characteristics of objects in our solar system including the Sun, planets, meteorites, comets,
asteroids, and moons; and
(B) describe types of equipment and transportation needed for space travel.
8.8 The student knows that matter is composed of atoms. The student is expected to:
(A) describe the structure and parts of an atom; and
(B) identify the properties of an atom including mass and electrical charge.
Exploratorium Science Snacks
http://www.exploratorium.edu/snacks/snackintro.html
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21 Oct 2005
Fun with the Photosphere: Magnetic Fields
Grades 5 – 8
Engage: (check PK, ignite interest)
Leading questions:
What is a magnet? (accept all responses. Hopefully, some kids say that the Earth is a magnet)
What does a magnet do? (accept all responses)
When I say magnetic field, what do you think of? (accept all responses)
Have you seen/played with a magnet and metals like iron or steel? What about iron filings?
Explore: (
Play video clip:
Some students may not have any prior knowledge of iron filings interacting with magnets.
Event
Show a magnet interacting with objects
(wood, iron, steel, copper, plastic)
Produce/show iron filings.
Even better, file down a piece of steel or
iron into filings (just a little to show)
Show a magnet interacting with iron
filings.
Show the fluid filled box
Insert magnet into mixture of fluid and
iron filings
Filings slowly align with the magnetic field
Filings fully align with the magnetic field
Facilitating
Which objects have magnetic properties?
What do you think the iron filings will do when I move the magnet
near them?
Tell students about the fluid and point out the iron filings.
Ask students to describe the iron filing patterns they see.
Explain: students explain uses of concepts in everyday life and science class
What do the iron filing patterns mean? What force is acting on the filings?
What would we see if we used a magnet with a much stronger magnetic field?
Elaborate: (transfer) how these processes are at work in the Sun based on empirical evidence
Play video clip of the magnet box beside a prominence. Let students compare the patterns.
Ask students to describe the prominence.
Tell students: Gas in the Sun's photosphere and chromosphere are part of the prominence. The gas is so hot (we can see it
emitting light) that sometimes it is electrically charged, and sometimes it is neutral. When the gas is electrically charged a
magnetic field can affect it, like the iron filings.
Do you see evidence of a magnetic field?
Are there other observations you made of the Sun that suggest magnetic fields interacting with the photosphere? (sunspot
structure)
Evaluate: (check for transfer) ask probing questions that force students to synthesize new concepts
with their existing understandings.
If the magnetic field changed shape, what would happen to the charged gas?
What would we see?
If the magnetic field's strength AND size increased, what would we see?
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The Lava Lamp Modeling a Solar Granule
Grades 5 - 8
Engage: (check PK, ignite interest)
Leading questions:
What happens when something floats?
Why do you think some things float, and others do not?
Where would you expect to see effects of convection? (everyday life)
McD Science Snack Experiment: What floats?
Materials: Large, clear container; an even number of equal mass objects – one or two must float in water.
What to do:
o Ask students which of these objects will float.
o Drop them into the water one by one. Let each one either sink or float.
o Ask students why they think some objects floated, while others sank.
o Accept all responses.
o Someone may claim that the heaviest objects sink, while the lightest objects float.
o Reveal that all the objects are the same weight. If necessary, show them via a balance.
One step closer to the lava lamp: Exploratorium Science Snack: Condiment Diver
http://www.exploratorium.edu/snacks/condiment_diver/index.html
o The step closer is changing the average density of the condiment baggie. That's what happens to the goocells in the lava lamp. But, the goo-balls change density due to a temperature change (Ideal Gas Law).
Explore Lava Lamp video clips:
Event
Show the initial state of the lava lamp
Point out the parts (light bulb, fluid)
Turn on the light bulb
Show clips of the lava lamp in various
stages of warming up
Show the lava lamp fully warmed up
Goo-cells rise and fall
Facilitating
What is happening?
What do you think will happen if I turn on the light bulb?
What is happening? (general pattern)
What do you think is light bulb is doing? Why?
What do you think the goo is doing? Why?
Describe the goo (shape and size)
Observe the general motion and pattern.
o What are the goo-cells doing?
Follow a goo-cell:
Pick one at the bottom. Direct attention to its size and shape.
Observe it rising - watch its size and shape.
o What is happening to the size and shape of the cell?
When it reaches the top, what does it do?
Observe it sinking – watch its size and shape
o What is happening to the size and shape of the cell?
Explain: students explain uses of concepts in everyday life and science class
Why did the goo-cells rise? How did their density change?
Elaborate: (transfer) how are these processes are at work in the Sun?
Lead students to discover that the Lava Lamp is a model of a solar granule.
o The photosphere of the Sun is made of gas cells, like the goo-cells in the Lava Lamp.
o The Sun's interior is much hotter, like the light bulb in the Lava Lamp.
Evaluate: (check for transfer) ask probing questions that help students to synthesize new concepts
with their existing understandings.
Ask students:
o If the photosphere were much cooler, what do you think would happen to the granules?
o What does that mean for the temperature of layers below the photosphere?
o If the gas in the granules slow down, what does that mean for the amount of energy the granule transports?
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