Transcript Combining Materials - Sonoma State University

NBSP Physical Science Leadership Institute
Combining Materials
Professor Lynn Cominsky
Joanne del Corral
Sharon Janulaw
Michelle Curtis
July 8, 2003
Standard Connections
 Students know that when two or more
substances are combined, a new substance may
be formed with properties that are different
than those of the original materials (3)
 Students know compounds are formed by
combining two or more different elements and
that compounds have properties that are
different from their constituent elements (8)
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First Activity:
Solids, liquids and gases
 Can you make a gas out of a solid and a
liquid?
 What substances are being combined, and
how are their properties changing?
 How can you tell if a new compound is
being formed?
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Equipment for first activity
 Given: Alkaseltzer tablet, water, a
balloon and a test tube
 Fill the test tube halfway with
water.
 Crush the tablet, and put about half
of it in the water in the test tube
 Quickly put the balloon over the
top of the test tube and then shake
it up.
 Write down your observations.
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Further investigations:
 How long will the balloon stay inflated?
 Is there a limit to how much Alkaseltzer you
can add to the test tube and still see the
same result?
 Can you try things that will slow down the
process? Speed it up?
 What compound is being formed?
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Further questions
 When the tablet dissolves, does the volume
of the system increase, decrease or stay the
same?
 When the tablet dissolves, does the mass of
the system increase, decrease or stay the
same?
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Standard Connections
 Students know the idea of atoms explains the
conservation of matter: In chemical reactions,
the number of atoms stays the same no matter
how they are arranged, so their total mass
stays the same (8)
 This means that the total mass of the gas in the
AlkaSeltzer experiment stays the same.
 How could we test this?
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Further investigations:
 Given: AlkaSeltzer, water, a film can and
paper
 Make a rocket out of the film can by
decorating it with paper
 GO OUTSIDE!
 Experiment with different amounts of
Alkaseltzer and water
 Cover the film can and place upside down
 What combination of materials makes the
best rocket?
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Standard Connections
 Some metals, such as steel and brass are
composed of a combination of elemental
metals. (5)
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Elements and Alloys
Material
Melting Point
Aluminum (Al) 660 oC
Copper (Cu)
1084.6 oC
Zinc (Zn)
Brass
Bronze
419.5 oC
915.5 oC
1038 oC
Steel
Iron (Fe)
1370
1538
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oC
oC
Prof. Lynn Cominsky
Density g/cm3
2.7
8.9
7.1
8.5
8.3
7.8
7.9
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Investigations for second activity
 How are alloys different than elements?
 Given: pieces of aluminum, copper, brass, bronze,
steel, iron, scales, graduated cylinders, water.
 Weigh and measure the volume of each item
 Calculate their density, compare to those in the
table. How do they compare?
 If you weren’t sure which sample was which, can
you now identify them?
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Further Investigations
 Use the shears to cut open two pennies
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One from before 1982
One from after 1982
 Compare and contrast the cut-open pennies
 What do you think has happened?
 What other differences would you predict in
the properties of these pennies?
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Key concepts: Alloys
 An alloy is composed of at least one metal, melted
together with another metal or a non-metal, then
cooled.
 Brass is an alloy of typically 70% Cu and 30% Zn
 A typical Bronze alloy would be 89% Cu, together
with 10% Al and 1% Fe
 Steel is an alloy of Iron, with about 10% Ni, 18%
Cr, and small amounts of C and Mn. There are
over 100 types of stainless steel.
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Vocabulary
 Alloy: material made of one metal and at
least one more metal or non-metal, melted
together
 Compound: a substance formed when atoms
of two or more elements join together
 Mixture: a material consisting of two or
more substances that are not chemically
bound to each other
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ELD Activities: Compare
 What familiar items are made of
brass, bronze or steel?
 Where in your house did you find
each item?
Item
Alloy
Where found
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ELD Activities: Visual Imagery
and Student Involvement
 Split the students into 2 teams, one with blue shirts, and
one with red shirts. (Or holding pieces of paper)
 Have them all stand in a circle holding hands, blue and red
students randomly mixed.
 Ask them to split into 2 groups, still with a mixture of both
colors, and hold hands in a straight line.
 Ask them to count how many red and blue students there
are in each group.
 What are the sums of the blue and red students from the
two groups?
 Note that no matter how the students are arranged, there is
always the same number of blue and red students.
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Publisher’s Materials
 Take some time to look through the stateadopted texts to find activities relating to
materials that have different properties when
combined.
 Examples: HM p. 64
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Break – something to think about
 Which do you think are more commonly
used, pure metals or alloys?
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Standard Connections
 Students know differences in chemical and
physical properties of substances are used to
separate mixtures and identify compounds (5)
 What is the difference between mixtures,
solutions and compounds?
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Mixtures and Solutions
 What is a mixture?
 How can some mixtures be separated?
 What is a solution?
 What factors affect how quickly a solution
will form?
 Can you separate a solution into its original
constituents?
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Third activity: Mix it up
 Given: coffee filter, scissors, 3
different water-soluble markers
(brown, green, black), small paper
cups, water
 Cut the coffee filter into 3 strips,
each 3 cm x 10 cm
 Touch a different color marker
near one end of each of the pieces
of filter paper
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http://www.bayerus.com/msm
s/fun/experiment/colors.html
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Third activity: Mix it up
 Put the bottom edge of each piece of filter paper in
a paper cup containing a small amount of water
 Observe what happens
 Which pigments made up the colors that you
tested?
 Why do you think some of the pigments traveled
farther up the paper than the others?
 What was being mixed?
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Fourth activity: Investigating Solutions
 Given: 3 plastic cups, ice, water, marker, sugar
cubes, stirring rod, timer, spoon
 Fill 3 different cups with equal amounts of water
that is: ice-cold water, room-temperature and warm.
Label the cups.
 Predict which water will more quickly dissolve the
sugar cube.
 Add a cube to each cup and time how long it takes
to dissolve the sugar.
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Fourth activity: Investigating Solutions
 Pour out the water and rinse out the cups.
 Refill one cup with warm water and add a
sugar cube. Stir the mixture until the cube
dissolves. Record the time.
 Use a spoon to crush a sugar cube. Add it to
a fresh cup of warm water and stir. Record
the time.
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Questions about Solutions:
 How did the temperature of the water affect the rate
that the sugar dissolved?
 What effect did stirring have on the rate?
 What effect did crushing the sugar cube have on the
rate?
 What can you infer about the size of the sugar
particles that are dissolved?
 How could you get the sugar back out of the water?
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Vocabulary and Key concepts:
 Homogeneous mixtures: all parts of the
mixture have the same composition, e.g.,
sugar cookie dough
 Heterogeneous mixtures: different parts of
the mixture have differing compositions,
e.g., chocolate chip cookie dough
 Solution: an act or the process by which a
solid, liquid, or gaseous substance is
homogeneously mixed with a liquid or
sometimes a gas or solid
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ELD Activities: Analogies
 Use the vocabulary words to create
analogies with common household
items
 Examples:
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Hot cocoa is a homogeneous solution:
it is milk and chocolate powder mixed
together
Hot cocoa with marshmallows is a ??
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ELD Activities: Academic Language
 Compare the use of the word solution in this
context vs. its alternate meaning of an
answer to a problem. Can you use both
words in sentences?
 Why do we say someone that is confused is
mixed-up?
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Publisher’s Materials
 Take some time to look through the stateadopted texts to find activities relating to
mixtures and solutions
 Examples: HM p. C54
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Lunch puzzler
 Why do alcohol and
water form a
solution, but oil and
water do not?
 What happens when
you add detergent to
a mixture of oil and
water? Why?
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Standard Connections
 Students know that during chemical reactions,
the atoms in the reactants rearrange to form
products with different properties (5)
 Students know… atoms may combine to form
molecules (5)
 Students know reactant atoms and molecules
interact to form products with different
chemical properties (8)
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Equipment for Fifth Activity:
Eruption!
 warm water
 plastic soda bottle
 dishwashing detergent
 food coloring
 Vinegar
 Baking soda
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Fifth Activity: Eruption!
Fill the bottle most of the way full with warm
water and a bit of red food color
 Add 6 drops of detergent to the bottle
contents.
 Add 2 tablespoons baking soda to the liquid.
 Slowly pour vinegar into the bottle.
 Put it in the sink or do this outside
 Watch out - eruption time!

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Key Concepts: Eruption!

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This experiment uses baking soda and vinegar
Vinegar is Acetic Acid: C2H4O2  CH3COOH
Baking Soda is NaHCO3
Carbon dioxide gas is being formed: CO2
HCO3-(aq) + H+(aq) = H2O(l) + CO2(g)
The gas bubbles out of the bottle, trapped in the
detergent/water/food coloring mixture.
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ELD Activities: Summing Up
 Write in your notebook a summary of what
you have learned about mixtures, solutions,
compounds, chemical reactions and alloys.
 Make sure to note the keywords that you use
to explain these concepts.
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Break – some things to think about
 From your knowledge of carbonated
beverages, what do you conclude about the
effect of temperature on the solubility of
carbon dioxide?
 What do you conclude about the effect of
pressure on the solubility of carbon dioxide?
(Think about a capped bottle vs. uncapped)
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Summing Up
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Element
Mixture
Compound
Made from one
atom
Made from more
than one type of
atom or molecule
Made from more
than one type of
atom or molecule
Homogeneous
Homogeneous or
Heterogeneous
Homogeneous
Separated by
nuclear reactions
Separated by
physical means
Separated by
chemical means
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Standard Connections
 Students know chemical reactions usually
liberate or absorb heat (8)
 Reactions that absorb heat are called
endothermic – how can we safely see this in a
classroom activity?
 Reactions that give off heat are called
exothermic – how can we safely see this in a
classroom activity?
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Sixth activity: Exothermic reaction
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Given: Thermometer, Jar with
Lid, Steel Wool, Vinegar
Place the thermometer in the jar
with vinegar and close the lid.
Allow about 5 minutes for the
thermometer to record the
temperature, then open the lid
and read the thermometer.
Remove the thermometer from
the jar (if you didn't already in
Step 1).
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Sixth activity: Exothermic reaction
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Soak a piece of steel wool in vinegar for 1
minute.
Squeeze the excess vinegar out of the steel wool.
Wrap the wool aroung the thermometer and place
the wool/thermometer in the jar, sealing the lid.
Allow 5 minutes, then read the temperature and
compare it with the first reading.
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Key concepts:
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The vinegar removes the protective coating on
the steel wool, and its acidity aids in oxidation
(rust) of the iron in the steel.
The thermal energy given off can be measured
by the rise in temperature seen by the
thermometer
The reaction is:
4 Fe (s) + 3O2 (g)  2 Fe2O3 + heat
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Seventh activity: Endothermic reaction
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Given: 25 ml citric acid solution, 15 g
baking soda, styrofoam cup,
thermometer, stirring rod
Pour the citric acid solution in a
styrofoam coffee cup.
Use a thermometer to record the initial
temperature.
Stir in the baking soda
Track the change in temperature as a
function of time.
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Key Concepts: Endothermic reaction
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The thermal energy taken in can be measured by
the fall in temperature seen by the thermometer
Once the reaction is complete, the temperature of
the mixture will return to room temperature.
The reaction is:
H3C6H5O7(aq) + 3 NaHCO3(s) + heat 
3CO2(g) + 3 H2O(l) + NaC6H5O7(aq) + 2Na+ (aq)
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Vocabulary
 Endothermic reaction: a chemical reaction
that absorbs heat
 Exothermic reaction: a chemical reaction
that gives off heat
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ELD Activities: Analogies and Student
Involvement
 What happens to your body when you run
or play sports?
 Have the students discuss with a partner
before you explain what happens.
 Have them write the main point in their
journal.
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Publisher’s Materials
 Take some time to look through the stateadopted texts to find activities relating to
chemical reactions of different types.
 Examples: HC p. C20
HC p. C33
HC p. C57
HM p. C64
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Lesson Study Activities
 Identify a key concept from today’s lecture
for further development
 Review the publisher’s materials about this
key concept
 Think about the best way to present this key
concept in your classroom
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Resources
 Physics by Inquiry – L. McDermott and the PEG
at U Washington
 http://chemistry.about.com/cs/howtos/
 http://www.1728.com/projects.htm
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