Download TEKS 8 - UNT College of Education

TEKS 8.9 A, C AND D
It was here just a moment ago!
TAKS Objective 3 – The student will demonstrate an
understanding of the structures and properties of matter.
Learned Science Concepts:

Matter is composed of atoms.

Substances have chemical and physical properties.

Complex interactions occur between matter and energy.
TEKS Science Concepts 8.9
The student knows that substances have chemical and physical
properties. The student is expected to:
(A) demonstrate that substances may react chemically to
form new substances;
(C) recognize the importance of formulas and equations
to express what happens in a chemical reaction; and
(D)
identify that physical and chemical properties
influence the development and application of
everyday materials such as cooking surfaces,
insulation, adhesive, and plastics.
TAKS Objective 3
page 1
TEKS 8.9 A, C, D
A
Overview
Students will learn to identify evidence of chemical change. By combining
a variety of substances, they will demonstrate different chemical changes
that produce change in color, change in temperature, production of gases,
and the production of precipitants. Students will also learn what a
chemical formula means and how scientists use formulas.
Instructional Strategies
Students will be involved in hands-on inquiry to demonstrate chemical
changes. Hands-on models will be used to build a concrete picture of
chemical formulas.
Objectives
1. The student will demonstrate chemical change as evidenced by a
change in color.
1. The student will measure temperature change as the result of a
chemical reaction.
2. The student will demonstrate a chemical reaction that produces gases.
3. The student will demonstrate a chemical change that results in the
formation of a precipitant.
4. The student will use models to explain chemical formulas.
TAKS Objective 3
page 2
TEKS 8.9 A, C, D
A
 For Teachers Eyes Only
Chemical Reactions
A chemical reaction, also called a chemical change, is material changing
from a beginning mass to a resulting substance. The process involves one
or more reactants yielding one or more products different from the
reactants. The characteristic of a chemical reaction is that new material or
materials are made and the original material disappears. A chemical
change could involve molecules attaching to each other to form larger
molecules, molecules breaking apart to form two, or more, smaller
molecules, or rearrangement of atoms within molecules. In order to make
transformations possible, chemical reactions usually involve the making or
breaking of chemical bonds. This does not mean that new elements have
been made. In order to make new elements, the nuclear contents must
change with the addition or subtraction of protons. An important aspect of
the definition is that a chemical reaction does not change the atomic
nucleus in any way, only the interaction of the electron clouds of the
involved atoms. Thus nuclear reactions are not chemical reactions.
Definition: A chemical change occurs whenever compounds are formed or
decomposed.
reactants disappear as chemical change occurs.
products appear as chemical change occurs.
catalysts speed up the reaction, but aren't produced or
consumed.
Microscopic view: A chemical change occurs whenever there is a
rearrangement of atoms that makes or breaks chemical bonds.
Chemical Equations
A chemical equation or formula is a way to describe what goes on in a
chemical reaction. Chemical equations are written with symbols. There is
an arrow pointing to the right that indicates the result of the chemical
change or the products. The materials to the left of the arrow are the
reactants. There are such things as reversible reactions, reactions in which
the products reassemble to become the original products. Reversible
reactions are symbolized in chemical equations by a double-headed arrow.
TAKS Objective 3
page 3
TEKS 8.9 A, C, D
A
Chemical Bonding
Chemical bonds form to lower the energy of the system in such a way the
components of the system become more stable. G. N. Lewis (1916)
suggested that bonds form to enable elements to attain a "noble gas
configuration". Chemical bonding involves sharing or transfer of
electrons, resulting in a more stable system. There are several types of
chemical bonds. Three basic types are:



ionic bonding, bonding between metals and non-metals involving the
transfer of electron(s). The substances are usually solid at room
temperature.
covalent bonding, bonding between non-metals and non-metals
involving sharing of electrons. The substances are usually gases or
liquids at room temperature.
metallic bonding, which simplistically can be considered as a
combination of both. They are generally solids at room temperature.
Types of Chemical Reactions
SYNTHESIS REACTIONS
A synthesis reaction might be symbolized by:
A+B
AB
A synthesis reaction occurs when two materials, elements or
compounds, come together to make a single product.
2 H2 + O2
2 H2O
What would you see in a ‘test tube’ if you were witness to a
synthesis reaction? You would see two different materials
combine. A single new material appears.
DECOMPOSITION REACTIONS
A single reactant comes apart into two or more products,
symbolized by:
XZ
X+Z
In a “test tube” you would see a single material coming apart into
more than one new material. For example heating sodium
TAKS Objective 3
page 4
TEKS 8.9 A, C, D
A
bicarbonate releases water and carbon dioxide and sodium
carbonate.
6 NaHCO3
3 Na2CO3 + 3 H2O + 3 CO2
SINGLE REPLACEMENT REACTIONS
A single replacement reaction occurs when silver nitrate solution
has a piece of copper placed into it. The solution begins to turn
blue and the copper seems to disappear. A silvery-white material
appears.
2 AgNO3 + Cu
Cu(NO3)2 + 2 Ag
DOUBLE REPLACEMENT REACTIONS
Let’s take an example.
AgNO3 + KCl
AgCl(s) + KNO3
The above equation tells only part of the story. Dissolved silver
nitrate becomes a solution of silver ions and nitrate ions.
Potassium chloride ionizes the same way. When the two solutions are
added together, the silver ions and chloride ions find each other and
become a solid precipitate. (They ‘rain’ or drop out of the solution, this
time as a solid.) Since silver chloride is insoluble in water, the ions take
each other out of the solution.
Ag+ + (NO3)- + K+ +Cl-
AgCl + K+ + (NO3)-
Another way to remove ions from a solution is to combine an acid and a
base. The two will neutralize forming water and a salt. One more way for
the ions to be taken out of the water is for some of the ions to escape as a
gas.
Conclusion
Chemical reactions are often accompanied by the appearance of gas, fire,
precipitate, color, light, sound, or odor. These phenomena are related to
energy and properties of the reactants and products. For example, the
oxidation of propane releases heat and light, and a rapid reaction is an
explosion. We study properties of substances so that we know how to
make use of them.
TAKS Objective 3
page 5
TEKS 8.9 A, C, D
A
It is important to remember that in a when a chemical change occurs and
energy is released or is absorbed, no loss in total molecular weight occurs.
In some reactions heat is given off (exothermic reactions), and in others
heat is absorbed (endothermic reactions). Furthermore, the new substances
formed differ from the original substances in the energy they contain.
Reversible reactions are those in which the chemical change taking place
may be paralleled by another change back to the original substances.
Adapted from online lectures of Clive Buckley
North East Wales Institute of Higher Education
TAKS Objective 3
page 6
TEKS 8.9 A, C, D
A
Student Misconceptions
 Misconception
Chemical changes are separate changes in substances
 Science Concept
Chemical changes involve interactions between molecules of the
substances.
Rebuild Concept
After the student has observed the characteristics of two separate
substances, combine them to cause a chemical change. Examine
the new substance. Point out that the new substance has very
different characteristics than either of the individual substance.
Also point out that the new substance cannot be separated back
into its original 2 substances.
 Misconception
Real chemicals are found in the chemistry laboratory and not
around the house.
 Science Concept
Chemicals that are found around the house are usually more
concentrated than teachers use with the students in lab due to
safety issues at school.
Rebuild Concept
Let students take some litmus paper home to test various solutions
found around their homes.
TAKS Objective 3
page 7
TEKS 8.9 A, C, D
A
Student Prior Knowledge
The student knows that substances have physical and chemical properties
and those substances can combine chemically to form new substances.
(TEKS 6.7 and 7.7)
TAKS Objective 3
page 8
TEKS 8.9 A, C, D
A
5 E’s
Engage
Engage 1
Demonstration: Balloon Gas
1. Before class place a couple of spoons of baking soda into a
balloon. Wipe off any evidence of balloon tampering.
2. Do this class demonstration without prior explanation. Pour
about 20 ml white vinegar into the balloon using a funnel.
Immediately clamp or tie the balloon shut.
3. Hold the balloon up for the class to observe it blowing itself
up.
4. Ask students what they think they just witnessed. Tell students
they will be demonstrating and observing chemical changes in
the explore activities.
Explore
Exploration 1
Activity: Red light – Green light
Class Time: 10 minutes
Objective: The student will demonstrate chemical change as evidenced by
a change in color.
TAKS Objective 3
page 9
TEKS 8.9 A, C, D
A
Materials
Vinegar
Ammonia
2 small beakers
cabbage juice or universal indicator
Goggles
Preparation Red cabbage juice can be made by placing chopped red
cabbage with water in a blender. Strain the blended juice. The cabbage can
also be cooked and the juice strained. Keep in the refrigerator to keep from
spoiling- will last ~10 days.
5. Place about 10 ml of cabbage juice in the portion cup.
6. Place about 5 drops of ammonia into the portion cup with cabbage
juice. Observe what happens.
7. Place about 10 drops of vinegar into the portion cup. Observe what
happens.
Exploration 2
Activity: For the rust of my life
Class Time: 20 minutes
Objective: The student will measure temperature change as the result of a
chemical reaction.
Process Skills:
TEKS 8.4 (A) – The student is expected to collect record, and
analyze information using thermometers or computer probes.
Materials:
Thermometer
Steel wool (soaked in vinegar)
Goggles
Jar with lid
TAKS Objective 3
page 10
TEKS 8.9 A, C, D
A
Teacher Preparation:
Students will need just enough steel wool to wrap around the bulb of their
thermometer. Soak steel wool in vinegar overnight in large beaker. Have
students pick up their piece of steel wool only when ready to use it. It is
the reaction of the soaked steel wool and the air that is producing the heat
in this reaction.
Procedure:
1. Record the temperature of the air _________________
2. Wrap the steel wool around the bulb of the thermometer.
3. Record the temperature every 30 seconds for 5 minutes
4. What happens?
Exploration 3
Activity: Take a Powder
Class Time: 10 minutes
Objective: The student will measure temperature change as the result of a
chemical reaction.
Process Skills:
TEKS 8.4 (A) – The student is expected to collect record, and
analyze information using thermometers or computer probes.
Materials:
Thermometer
Baking powder
Baking Soda
Vinegar
Water
Goggles
2 plastic spoons
2 portion cups or small beakers
Procedure:
TAKS Objective 3
page 11
TEKS 8.9 A, C, D
A
1. Place 2 spoons of baking powder and the thermometer in the portion
cup.
2. Add 20 ml water and stir.
3. Record the temperature after 15 seconds.
4. Place 2 spoon of baking soda and the thermometer in a clean portion
cup.
5. Add 10 ml of vinegar.
6. Record the temperature after 15 seconds.
7. Compare the two processes.
Exploration 4
Activity: Clabbered Clumps
Class Time: 10 minutes
Objective: The student will demonstrate a chemical change that results in
the formation of a precipitant.
Materials:
Milk
White vinegar
Goggles
Portion cup or beaker
Procedure:
1. Place 20 ml of milk in the portion cup.
2. Add 20 ml white vinegar and stir.
3. Observe what happens.
Exploration 5
Activity: Witches Brew
Class Time: 10 minutes
TAKS Objective 3
page 12
TEKS 8.9 A, C, D
A
Objective: The student will demonstrate a chemical reaction that produces
gases.
Materials:
Baking soda
White vinegar colored with green food coloring
Goggles
Plastic spoon
Large beaker
Procedure:
4. Place 2 spoons of baking soda in the beaker.
5. Add 20 ml of the vinegar.
6. Observe what happens.
Exploration 6
Activity: Bubble Bubble Toil and Trouble
Class Time: 15 minutes
Objective: The student will demonstrate a chemical reaction that
produces gases.
Materials
250 mL Beaker
Nine-volt battery or Lantern Battery
Two 14-18 Gauge wires to connect to terminals of battery (strip off
0.5 cm of insulation from both ends of wire)
200 mL Distilled water
Salt
Procedure As a result of this activity both hydrogen and chlorine gases
will be produced. The chorine gas might be distinguished by smell.
1. Connect the wires to the battery
2. Fill the beaker with water about 2/3 full.
3. Place the battery wires into the water. DO NOT let the ends of the
wires touch. What happens? Nothing
4. Put 10-30 ml of salt in water and stir until dissolved.
TAKS Objective 3
page 13
TEKS 8.9 A, C, D
A
5. Place the battery wires back in the water. DO NOT let the ends of the
wires touch. What happens? It bubbles.
6. The chlorine gas may give off a noticeable odor.
Exploration 7
Go to the following website:
http://www.learnalberta.ca/content/secs/html/matter_and_chemical_chang
e/ChemicalAndPhysicalChange/index.html
In the lower right hand corner, click on the word, “guide” and then close
the blue introduction frame. You may close the blue introduction frame by
clicking on the “X” located at the top right hand corner of the blue
introduction frame.
View each of the 10 videos which are titled below. Answer the following
questions for each video listed below. Remember the neumonic:
–
–
–
–
–
Please- Precipitate (2 clears make cloudy)
Excuse- Energy change (heat, light, sound, electricity)
Coughs- Color change (unexpected)
Sneezes- Smell Change
Burps- Bubbles or fizzing (gas produced)
Video 1 - Blazing Glory
1. What happens when glycerine is added to the container of
potassium permanganate? Smoke, fire, bubbles
2. Is this a physical or chemical change? Chemical
Video 2 – Tiny Bubbles
1. What is the first measuring tool used in this experiment? Digital
balance
2. What is added to the beaker? Nitric acid and copper
3. What happens? The solution bubbles and the temperature goes up.
4. Is this a physical or chemical change? Chemical
Video 3 – Gone but Not Lost
1. How much water is in the test tube? 5 ML
2. What is added to the test tube? Sodium acetate trihydrate and water
3. What happens? The solution bubbles and the temperature goes up.
TAKS Objective 3
page 14
TEKS 8.9 A, C, D
A
4. Is this a physical or chemical change? Chemical
Video 4 – Shower of Yellow
1. What containers are shown in this video? Beaker, flask, test tube,
graduate cylinder
2. Is this a physical or chemical change?
Video 5 – Seeding Crystals
1. What happens when sodium acetate is added to water? White
crystals are formed and a drop of condensate forms at the bottom
of the test tube.
2. Is this a physical or chemical change? Chemical
Video 6 – Swell Marshmallows
1. What happens to the marshmallow when the pressure is increased?
They puff up
2. What happens to the marshmallow when the pressure is decreased?
They shrink down
3. Is this a physical or chemical change? Physical
Video 7 – Sugar Power
1. What happens when sugar and potassium chlorate are combined?
nothing
2. What happens when sulphuric acid is added to sugar and
potassium? It flames
3. Is this a physical or chemical change? Chemical
Video 8 – Cold but Sublime
1. What happens when dry ice is added to water? It melts
2. Is this a physical or chemical change? Physical
Video 9 – Now That’s A Gas
1. What happens when water and phenolphthalein indicator are
combined? nothing
2. What happens when water and phenolphthalein solutions are
combined with calcium carbide? The solution turns fink and fizzes
3. Is this a physical or chemical change? Chemical
TAKS Objective 3
page 15
TEKS 8.9 A, C, D
A
Video 10 – Trading Places
1. What happens when copper chloride is combined with aluminum?
It bubbles and fizzes
2. Is this a physical or chemical change? chemical
Explain
Ask students what evidence suggested a chemical change in each of the
explore activities. Students should have observed smell changes, color
changes, energy changes (heat, light, sound, electricity, etc),
bubbles/fizzing &/or formation of precipitants.
Elaborate
Elaboration 1
Activity: Abracadabra
Class Time: 1 class period
Objective: The student will systematically test for evidence of a chemical
reaction.
Materials
Bottle A (contains tap water)
Bottle B (contains white vinegar)
Bottle C (contains sodium thiosulfate- 62 g sodium thiosulfate to
500 mL water = 0.5M solution)
Powder 1 (baking soda)
Powder 2 (sodium chloride)
Powder 3 (calcium chloride)
Litmus paper
Clear plastic cups or beakers
TAKS Objective 3
page 16
TEKS 8.9 A, C, D
A
Plastic spoons
Thermometer
Abracadabra Data Sheet (see Black Line Masters)
Preparation: Before class label the solutions and powders as shown in the
materials list. The actual name should be unknown to students.
Procedure: Students should investigate what happens when 2 unknown
substances are mixed. Only two substances should be mixed (ex. 10 ml
from bottle A could be mixed with a spoon for powder 1). Students should
record changes in temperature, pH (litmus is red in acid, blue in base),
color, formation of gas, or formation of precipitate.
Elaboration 2
Activity: Sweet Models
Class Time: 30 minutes
Objective: The student will use models to explain chemical formulas.
Materials
playdough spheres (red, yellow, blue), or gumdrops, m&m’s, skittles
Paper place mat
Procedure
1. Make four spheres of each color playdough. Each blue sphere
represents one hydrogen atom, red spheres represent oxygen atoms and
yellow spheres represent carbon atoms.
2. Attach the spheres as described to build molecules. Fill in your data
table as you go.
a. water: H2O: connect 2 hydrogens to one center oxygen.
b. carbon dioxide: CO2: connect 2 oxygens to one center carbon.
c. methane: CH4: connect four hydrogens to one center carbon.
TAKS Objective 3
page 17
TEKS 8.9 A, C, D
A
DATA
Chemical
name
Chemical
formula
Number of atoms in compound
Hydrogen
Carbon
Oxygen
Total
Water
Carbon
dioxide
Methane
1. In a molecule of fruit sugar, C6H12O6, how many carbon atom are
there? Hydrogen? Oxygen?
2. Which formulas represent compounds? Elements? (NaCl, Ag, Co,
CO, SO2, AgBr)
3. Nitrogen in the air is two nitrogen atoms attached together, N2. Is this
nitrogen a compound or element? How do you know?
TAKS Objective 3
page 18
TEKS 8.9 A, C, D
A
So Happy Together!
Most solids, liquids and gases exist because of their ability to combine, or
chemically bond, with other elements to make new substances called
compounds. Bonds are created when chemical reactions occur,
rearranging atoms and share or transfer electrons. Once bonds are made,
atoms hang on tightly to their new partners. It is difficult to split new
compounds apart.
Each of these groupings shows the atoms that create compounds. Write
the formula that shows the makeup of the compound.
__________ 1. hydrogen chloride
H
__________ 2. ammonia
Cl
H
N
H
H
__________ 3. water
H
O
H
H
__________ 5. carbon dioxide
O
__________ 4. hydrogen peroxide
C
O
O
H
__________ 6. sand (silicon
dioxide)
O
O
TAKS Objective 3
page 19
Si
O
TEKS 8.9 A, C, D
A
__________ 7. diphosphorous
pentoxide
__________ 8. chalk (calcium
carbonate)
O
O
O
O
P
P
C
Ca
O
O
O
O
__________ 9. baking soda
(sodium bicarbonate
__________ 10. methane
O
Na
H
H
H
C
C
O
O
__________ 11. salt (sodium
chloride)
Na
__________ 12. carbon monoxide
Cl
_________ 13. silver nitrate
H
H
O
C
_________ 14. nitrogen dioxide
O
O
N
O
N
O
Ag
O
TAKS Objective 3
page 20
TEKS 8.9 A, C, D
A
Elaboration 3
Activity: Irreversible Consequences
Class Time: 20 minutes (not allowing for drying time
Materials
Baking soda
White vinegar
Plastic spoon
Evaporating dish
Procedure:
1. Place about ½ spoon full of baking soda in an evaporating dish. Add 2
mL of white vinegar.
2. Allow the mixture to dry.
3. Examine the result and compare it with baking soda. Do they look the
same?
4. To find out, add 2 mL of vinegar to the substance remaining in the
dish and observe.
Questions:
1. Did a chemical reaction occur in step 1? Explain. Yes, it was an
endothermic reaction with fizzing. Carbon dioxide was produced.
2. Are the chemical properties of the residue the same as those of baking
soda? Explain. No, adding more vinegar does not create the same
reaction.
Elaboration 4
Take it home: Chemistry at home
Objective: Identify that physical and chemical properties influence the
development and application of everyday materials such as cooking
surfaces, insulation, adhesive, and plastics
If a student looks carefully, they will spot many chemical reactions going
on right in their own kitchen. Have students make a list of 10 chemical
reactions observed at home. Upon returning to class, have the students
write a list of ideas they have developed about chemical reactions freely in
a paragraph without worrying about punctuation, spelling and grammar.
TAKS Objective 3
page 21
TEKS 8.9 A, C, D
A
Elaboration 5
Objective: Observe physical and chemical properties of chemicals.
The students will use technology to view videos associated with physical
and chemical properties of chemicals (see blackline master). Go to the
following website:
http://www.learnalberta.ca/content/secs/html/matter_and_chemical_chang
e/ChemicalAndPhysicalChange/index.html
Elaboration 6
Objective: Recognize compounds, interpret chemical formulas and
recognize balanced equations.
The student will use prior information they have learned about elements to
recognize compounds and chemical formulas. The student will fill in the
missing piece to create a balanced equation (see blackline master)..
Evaluate
1. How many molecules of copper are produced from two molecules of
Cu2O? 4
2. What happens to atoms in a chemical reaction?
3. What physical properties can change in a chemical reaction?
TAKS Objective 3
page 22
TEKS 8.9 A, C, D
A
TAKS Objective 3
page 23
TEKS 8.10 A
Mixing it up Lab Guide
In this lab, we’re going to combine different substances and see if a chemical change
takes place. To do this, we need to remember the five events that evidence a chemical
change (remember our mnemonic – Please Excuse Coughs, Sneezes, and Burps): (1) the
formation of a precipitant, (2) energy release or absorbed, (3) unexpected color change,
(4) smell change, and (5) the formation of bubbles (which tells us that a gas has been
formed). Additionally, we’re going to learn to test the pH of liquids by using strips of
litmus paper, which change different colors depending on the pH of the liquid in which
they are immersed.
Record the color of each substance in the following table:
Vinegar
Sodium
Thiosulfate
Water
Morton Iodized
Salt
Baking Soda
Use the litmus paper strips to determine the pH of each individual liquid:
Vinegar
Sodium
Thiosulfate
Tap Water
Morton Iodized
Salt
Baking Soda
8
7
When measuring out substances, use the following quantities: Vinegar – 10 drops;
Sodium Thiosulfate – 10 drops; Tap Water – 10 drops; Morton Iodized Salt – ½
teaspoon; Baking Soda – ½ teaspoon.
TAKS Objective 3
page 24
TEKS 8.10 A
TRIAL 1: Next, you will choose two substances to combine. You may either combine a
liquid with a liquid or a solid with a liquid. Circle YES or NO for the questions in each
trial, and complete any follow-up questions, if necessary.
First Substance ____________________
Second Substance ____________________
Was a precipitant formed? (Remember, you can only have a precipitant if you are
combining liquids) YES
NO
If yes, was a solid or a cloudy liquid formed?
Was energy released or absorbed? YES
NO
If yes, what was the form of the energy released or absorbed?
Did you see a color change?
YES
NO
If yes, what color is the product?
Does the combination smell different from the initial substances? YES
Were bubbles formed? YES
NO
NO
What is the pH of the combination?
TRIAL 2: Next, you will choose two substances to combine. You may either combine a
liquid with a liquid or a solid with a liquid.
First Substance ____________________
Second Substance ____________________
Was a precipitant formed? (Remember, you can only have a precipitant if you are
combining liquids) YES
NO
If yes, was a solid or a cloudy liquid formed?
Was energy released or absorbed? YES
NO
TAKS Objective 3
page 25
TEKS 8.10 A
If yes, what was the form of the energy released or absorbed?
Did you see a color change?
YES
NO
If yes, what color is the product?
Does the combination smell different from the initial substances? YES
Were bubbles formed? YES
NO
NO
What is the pH of the combination?
TRIAL 3: Next, you will choose two substances to combine. You may either combine a
liquid with a liquid or a solid with a liquid.
First Substance ____________________
Second Substance ____________________
Was a precipitant formed? (Remember, you can only have a precipitant if you are
combining liquids) YES
NO
If yes, was a solid or a cloudy liquid formed?
Was energy released or absorbed? YES
NO
If yes, what was the form of the energy released or absorbed?
Did you see a color change?
YES
NO
If yes, what color is the product?
Does the combination smell different from the initial substances? YES
TAKS Objective 3
page 26
NO
TEKS 8.10 A
Were bubbles formed? YES
NO
What is the pH of the combination?
TRIAL 4: Next, you will choose two substances to combine. You may either combine a
liquid with a liquid or a solid with a liquid.
First Substance ____________________
Second Substance ____________________
Was a precipitant formed? (Remember, you can only have a precipitant if you are
combining liquids) YES
NO
If yes, was a solid or a cloudy liquid formed?
Was energy released or absorbed? YES
NO
If yes, what was the form of the energy released or absorbed?
Did you see a color change?
YES
NO
If yes, what color is the product?
Does the combination smell different from the initial substances? YES
Were bubbles formed? YES
NO
NO
What is the pH of the combination?
TAKS Objective 3
page 27
TEKS 8.10 A
TRIAL 5: Next, you will choose two substances to combine. You may either combine a
liquid with a liquid or a solid with a liquid.
First Substance ____________________
Second Substance ____________________
Was a precipitant formed? (Remember, you can only have a precipitant if you are
combining liquids) YES
NO
If yes, was a solid or a cloudy liquid formed?
Was energy released or absorbed? YES
NO
If yes, what was the form of the energy released or absorbed?
Did you see a color change?
YES
NO
If yes, what color is the product?
Does the combination smell different from the initial substances? YES
Were bubbles formed? YES
NO
NO
What is the pH of the combination?
Circle the five combinations that you tested:
Vinegar + Sodium
Thiosulfate
Water + Vinegar
Sodium Thiosulfate +
Water
Vinegar + Salt
Water + Salt
Sodium Thiosulfate + Salt
Vinegar + Baking Soda
Water + Baking Soda
Sodium Thiosulfate +
Baking Soda
TAKS Objective 3
page 28
TEKS 8.10 A
Sweet Models
Class Time: 30 minutes
Objective: The student will use models to explain chemical formulas.
Materials
playdough spheres (red, yellow, blue), or gumdrops, m&m’s, skittles
Paper place mat
Procedure
1. Make four spheres of each color playdough. Each blue sphere represents one
hydrogen atom, red spheres represent oxygen atoms and yellow spheres represent
carbon atoms.
2. Attach the spheres as described to build molecules. Fill in your data table as you go.
a. water: H2O: connect 2 hydrogens to one center oxygen.
b. carbon dioxide: CO2: connect 2 oxygens to one center carbon.
c. methane: CH4: connect four hydrogens to one center carbon.
TAKS Objective 3
page 29
TEKS 8.10 A
DATA
Chemical
name
Chemical
formula
Number of atoms in compound
Hydrogen
Carbon
Oxygen
Total
Water
Carbon
dioxide
methane
1. In a molecule of fruit sugar, C6H12O6, how many carbon atom are there? Hydrogen?
Oxygen?
2. Which formulas represent compounds? Elements? (NaCl, Ag, Co, CO, SO2, AgBr)
3. Nitrogen in the air is two nitrogen atoms attached together, N2. Is this nitrogen a
compound or element? How do you know?
TAKS Objective 3
page 30
TEKS 8.10 A
So Happy Together!
Most solids, liquids and gases exist because of their ability to combine, or chemically
bond, with other elements to make new substances called compounds. Bonds are created
when chemical reactions occur, rearranging atoms and share or transfer electrons. Once
bonds are made, atoms hang on tightly to their new partners. It is difficult to split new
compounds apart.
Each of these groupings shows the atoms that create compounds. Write the formula that
shows the makeup of the compound.
__________ 1. hydrogen chloride
H
__________ 2. ammonia
Cl
H
N
H
H
__________ 3. water
H
O
__________ 4. hydrogen peroxide
H
H
__________ 5. carbon dioxide
O
C
O
O
H
__________ 6. sand (silicon dioxide)
O
O
TAKS Objective 3
page 31
Si
O
TEKS 8.10 A
__________ 7. diphosphorous pentoxide
O
O
__________ 8. chalk (calcium carbonate)
O
P
P
O
C
Ca
O
O
O
O
__________ 9. baking soda (sodium
bicarbonate
__________ 10. methane
O
Na
H
H
H
C
C
O
O
__________ 11. salt (sodium chloride)
Na
__________ 12. carbon monoxide
Cl
_________ 13. silver nitrate
H
H
O
C
_________ 14. nitrogen dioxide
O
O
O
N
N
O
Ag
O
TAKS Objective 3
page 32
TEKS 8.10 A
Compounds, Chemical Formulas, and Chemical Equations
For each of the following:
(a) List the elements.
(b) Indicate how many atoms there are for each element on each side of the equation.
(c) Complete the missing information so that each side of the equation in balance.
1. 2C2H6 + 7O2 → 4CO? + 6H2O
Ethane + Oxygen yields Carbon Dioxide + Water
(a)
(b)
(c)
2. ?Al + 3O2 → 2Al2O3
Aluminum + Oxygen yields Aluminum Oxide
(a)
(b)
(c)
TAKS Objective 3
page 33
TEKS 8.10 A
3. CO2 + 4H2 → CH4 + H?O
Carbon Dioxide + Hydrogen yields Methane + water
(a)
(b)
(c)
4. ?Mg + P4 → 2Mg3P2
Magnesium + Phosphorus → Magnesium Phosphide
(a)
(b)
(c)
5. 2H2 + O? → 2H2O
Hydrogen + Oxygen yields water
(a)
(b)
(c)
TAKS Objective 3
page 34
TEKS 8.10 A
6. K2O + H2O → ?KOH
Potassium oxide + water yields potassium hydroxide
(a)
(b)
(c)
7. I2 + 2Na2S2O3 → 2NaI + Na?S4O6
Iodine + Sodium Thiosulphate yields Aluminum Oxide + Copper
(a)
(b)
(c)
8. ?Al + 3CuO → Al2O3 + 3Cu
Aluminum + Copper Oxide yields Aluminum Oxide + Copper
(a)
(b)
(c)
TAKS Objective 3
page 35
TEKS 8.10 A
9. C?H8 + 5O2 → 3CO2 + 4H2O
Propane + Oxygen yields Carbon Dioxide + water
(a)
(b)
(c)
10. 3H2 + N2 → 2NH?
Hydrogen + Nitrogen yields ammonia
(a)
(b)
(c)
11. List the names of five elements from problems 1-10 above.
12. List the names of five compounds from problems 1-10 above.
13. Describe in words how to calculate the number of hydrogen and oxygen atoms for
the following: 6H2O
TAKS Objective 3
page 36
TEKS 8.10 A
Chemical Formulae and Equations
For each of the following, identify the elements present and the number of atoms of each
element in the molecule.
1. Aspirin - C9H8O4
Elements Present
Number of Atoms
of each Element
2. Tylenol - C8H9NO2
Elements Present
Number of Atoms
of each Element
3. Coke - C17H21NO4
Elements Present
Number of Atoms
of each Element
4. Bleach - NaOCl
Elements Present
Number of Atoms
of each Element
5. Caffeine - C8H10N4O2
Elements Present
Number of Atoms
of each Element
6. Hydrogen peroxide - H2O2
Elements Present
Number of Atoms
of each Element
7. Rubbing alcohol - C6H12O6
TAKS Objective 3
page 37
TEKS 8.10 A
Elements Present
Number of Atoms
of each Element
8. Sugar - NH3
Elements Present
Number of Atoms
of each Element
9. Table salt - NaCl
Elements Present
Number of Atoms
of each Element
10. Benzoyl peroxide - C14H10O4
Elements Present
Number of Atoms
of each Element
11. wintergreen flavor - C8H8O3
Elements Present
Number of Atoms
of each Element
12. Lotion - CH4N2O
Elements Present
Number of Atoms
of each Element
TAKS Objective 3
page 38
TEKS 8.10 A
13. Ethanol - C2H5OH
Elements Present
Number of Atoms
of each Element
14. Theobromine (main ingredient of chocolate) - C7H8N4O2.
Elements Present
Number of Atoms
of each Element
15. Lycopene (bright red pigment in a tomato) - C40H56
Elements Present
Number of Atoms
of each Element
16. Corn Syrup - C6H12O6 + H2O
Elements Present
Number of Atoms
of each Element
Vocabulary:
An atom is a unit of matter, the smallest unit of an element, having all the characteristics
of that element and consisting of a dense, central, positively charged nucleus surrounded
by a system of electrons.
A molecule is the smallest physical unit of an element or compound, consisting of one or
more like atoms in an element (e.g., H, O, or N etc.) and two or more different atoms in a
compound (e.g.,. H2O, CO2, etc.).
TAKS Objective 3
page 39
TEKS 8.10 A
Use the formulae given the answer the questions concerning the formulae.
Water → Hydrogen + Oxygen
2H2O → 2H2 + O2
1. How many molecules are on the left side of the equation?
2. How many molecules are on the right side of the equation?
3. How many H atoms are on the left side of the equation?
4. How many H atoms are on the right side of the equation?
5. How many molecules are in O2?
____
6. How many O atoms are in 2H2O?
____
7. How many H atoms are in 2H2?
____
____
____
____
____
Methane + Oxygen → Carbon Dioxide + Water
CH4 + 2O2 →
CO2 + 2H2O
8. How many molecules are on the left side of the equation?
9. How many molecules are on the right side of the equation?
10. How many C atoms are there in CH4? ____
11. How many H atoms are there in CH4? ____
12. How many H atoms are there in 2H2O? ____
13. How many O atoms are there in 2H2O? ____
____
____
Sodium + Water → Sodium Hydroxide
Na2O + H2O → 2NaOH
14. How many molecules are on the left side of the equation?
15. How many molecules are on the right side of the equation?
16. How many Na atoms are there in Na2O?
____
17. How many O atoms are there in Na2O?
____
18. How many Na atoms are there in 2NaOH?
____
19. How many O atoms are there in 2NaOH?
____
20. How many H atoms are there in 2NaOH?
____
carbon dioxide + water + light energy →
glucose +
____
____
oxygen
6CO2 + 6H2O + photons → C6H12O6 + 6O2
21. How many molecules are on the left side of the equation?
22. How many molecules are on the right side of the equation?
23. How many molecules are in 6CO2?
____
24. How many molecules are in C6H12O6? ____
25. How many H atoms are in 6H2O?
____
26. How many O atoms are in 6CO2?
____
27. How many C atoms are in C6H12O6?
____
TAKS Objective 3
page 40
____
____
TEKS 8.10 A
28. Draw 2NaOH:
TAKS Objective 3
page 41
TEKS 8.10 A
Chemical Equations
Vocabulary
Molecule – two or more atoms combined
Element – a pure substance made of only one kind of atom
Compound – a substance made of more than one kind of atom
Physical Change – a change in which no new substances are produced
Chemical Change – a change in which new substances are produced
A chemical equation describes what happens in a chemical reaction (a reaction in which a
chemical change occurs). It is important to note that in a chemical reaction:
(a) atoms are NOT destroyed
(b) atoms are NOT created
(c) atoms are NOT changed into other kinds of atoms
So if none of these things happen in a chemical reaction, just what do we mean when we
say “new substances are produced in a chemical reaction”? We mean that the atoms in
the molecules on the left side of the arrow are rearranged into the molecules on the right
side of the arrow.
A correctly written chemical equation will be balanced. This means that there are equal
numbers of each kind of atom on both sides of the arrow.
Directions:
(1) For each of the following, count up the number of atoms of each element on both
sides of the equation to determine whether each equation is balanced.
(2) Also, draw the molecules present on each side of equation in the space provided.
1. The following chemical equation describes the hydrolysis of water in which water is
broken down into hydrogen gas and oxygen gas.
Water
yields
2H2O
→
Hydrogen and Oxygen
2H2
H=
H=
O=
O=
H
+
O2
Is the equation balanced?
H
H
O
H
→
H
H
O
+
H
H
O
O
TAKS Objective 3
page 42
TEKS 8.10 A
2. The following chemical equation describes carbonic acid breaking down into water
and carbon dioxide (the bubbles in soda).
Carbonic Acid yields Water
H2CO3
→
and
Carbon Dioxide
+
CO2
H2O
Is the equation balanced?
3. The following equation describes the combustion of propane gas in which propane and
oxygen form carbon dioxide and water.
Propane and Oxygen yield Carbon Dioxide and Water
C3H8
+
5O2
→
3CO2
+ 4H2O
Is the equation balanced?
4. The following equation describes the photosynthesis, in which carbon dioxide and
water react to form glucose (a simple sugar), oxygen gas, and water.
Carbon Dioxide and Water and Light Energy yield Glucose and Oxygen and Water
6CO2
+ 12H2O +
photons
→ C6H12O6 +
6O2
+ 6H2O
Is the equation balanced?
TAKS Objective 3
page 43
TEKS 8.10 A
Chemistry Computer Lab
Go to the following website:
http://www.learnalberta.ca/content/secs/html/matter_and_chemical_change/ChemicalAnd
PhysicalChange/index.html
In the lower right hand corner, click on the word, “guide” and then close the blue
introduction frame. You may close the blue introduction frame by clicking on the “X”
located at the top right hand corner of the blue introduction frame.
View each of the 10 videos which are titled below. Answer the following questions for
each video listed below. Remember the neumonic:
–
–
–
–
–
Please- Precipitate (2 clears make cloudy)
Excuse- Energy change (heat, light, sound, electricity)
Coughs- Color change (unexpected)
Sneezes- Smell Change
Burps- Bubbles or fizzing (gas produced)
Video 1 - Blazing Glory
1. What happens when glycerine is added to the container of potassium
permanganate?
2. Is this a physical or chemical change?
Video 2 – Tiny Bubbles
3.
What is the first measuring tool used in this experiment?
4. What is added to the beaker?
5. What happens?
6. Is this a physical or chemical change?
Video 3 – Gone but Not Lost
7.
How much water is in the test tube?
8. What is added to the test tube?
9. What happens?
10. Is this a physical or chemical change?
TAKS Objective 3
page 44
TEKS 8.10 A
Video 4 – Shower of Yellow
11. What containers are shown in this video?
12. Is this a physical or chemical change?
Video 5 – Seeding Crystals
13. What happens when sodium acetate is added to water?
14. Is this a physical or chemical change?
Video 6 – Swell Marshmallows
15. What happens to the marshmallow when the pressure is increased?
16. What happens to the marshmallow when the pressure is decreased?
17. Is this a physical or chemical change?
Video 7 – Sugar Power
18. What happens when sugar and potassium chlorate are combined?
19. What happens when sulphuric acid is added to sugar and potassium
20. Is this a physical or chemical change?
Video 8 – Cold but Sublime
21. What happens when dry ice is added to water?
22. Is this a physical or chemical change?
TAKS Objective 3
page 45
TEKS 8.10 A
Video 9 – Now That’s A Gas
23. What happens when water and phenolphthalein indicator are combined?
24. What happens when water and phenolphthalein solutions are combined with
calcium carbide?
25. Is this a physical or chemical change?
Video 10 – Trading Places
26. What happens when copper chloride is combined with aluminum?
27. Is this a physical or chemical change?
TAKS Objective 3
page 46
TEKS 8.10 A
TAKS ObjectiveTEKS
3 8.10
pageA 47