Combining Materials Professor Lynn Cominsky Joanne del Corral Sharon Janulaw Michelle Curtis July 8,...

Combining Materials

Professor Lynn Cominsky

Joanne del Corral

Sharon Janulaw

Michelle Curtis

July 8, 2003

NBSP Physical Science Leadership Institute

7/8/2003 Prof. Lynn Cominsky 2

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)


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?


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.


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?


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?



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?


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?



Some metals, such as steel and brass are composed of a combination of elemental metals. (5)


Elements and Alloys

Aluminum (Al) 660 oC 2.7

Copper (Cu) 1084.6 oC 8.9

Zinc (Zn)

Brass

419.5 oC

915.5 oC

7.1

8.5

Bronze 1038 oC 8.3

Steel

Iron (Fe)

1370 oC

1538 oC

7.8

7.9

Material Melting Point Density g/cm3


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?


Further Investigations

Use the shears to cut open two pennies 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?


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.


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


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


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.


Publisher’s Materials

Take some time to look through the state-adopted texts to find activities relating to materials that have different properties when combined.

Examples: HM p. 64


Break – something to think about

Which do you think are more commonly used, pure metals or alloys?



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?


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?


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

http://www.bayerus.com/msms/fun/experiment/colors.html


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?


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.


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.


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?


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


ELD Activities: Analogies

Use the vocabulary words to create analogies with common household items

Examples: Hot cocoa is a homogeneous solution:

it is milk and chocolate powder mixed together

Hot cocoa with marshmallows is a ??


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?



Take some time to look through the state-adopted texts to find activities relating to mixtures and solutions

Examples: HM p. C54


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?



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)


Equipment for Fifth Activity: Eruption!

warm water plastic soda bottle dishwashing detergent food coloring Vinegar Baking soda


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!


Key Concepts: Eruption!

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.


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.


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)


Summing Up

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



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?


Sixth activity: Exothermic reaction

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).


Sixth activity: Exothermic reaction

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.


Key concepts:

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


Seventh activity: Endothermic reaction

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.


Key Concepts: Endothermic reaction

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)


Vocabulary

Endothermic reaction: a chemical reaction that absorbs heat

Exothermic reaction: a chemical reaction that gives off heat


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.



Take some time to look through the state-adopted texts to find activities relating to chemical reactions of different types.

Examples: HC p. C20 HC p. C33 HC p. C57 HM p. C64


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


Resources

Physics by Inquiry – L. McDermott and the PEG at U Washington

http://chemistry.about.com/cs/howtos/ http://www.1728.com/projects.htm

Date post:	25-Dec-2015
Category:	Documents
Upload:	darcy-blake-haynes
View:	217 times
Download:	2 times

Combining Materials Professor Lynn Cominsky Joanne del Corral Sharon Janulaw Michelle Curtis July 8,...

Documents