Aldine I.S.D.
Science Grade 8
8.9C (Old) TEKS and 8.5D (New) TEKS
Chemical Formulas
LESSON
PLAN
Summary
In order to make it easier to describe elements and molecules, chemical formulas are used. For
example, H represents one atom of hydrogen and "O" represents one atom of oxygen. If we
want to represent two atoms of hydrogen, instead of writing H H, we write H2. The subscript
"2" means that two atoms of the element hydrogen have joined together to form a molecule. A
subscript is only used when more than one atom is being represented. The graphic below
illustrates the formula for water using symbols.
TEKS
(Old TEKS) – 8.9C The student will be able to recognize the importance of formulas and
equations to express what happens in a chemical reaction.
(New TEKS) – 8.5D The student will recognize that chemical formulas are used to identify
substances and determine the number of atoms of each element in chemical
formulas containing subscripts.
College Readiness Standards
VII. Chemistry
F. Chemical nomenclature
1. Know formulas for ionic compounds.
2. Know formulas for molecular compounds.
ELPS
1A – Use prior knowledge to understand meanings
1C – Use techniques such as concept mapping, drawing, memorizing, comparing, contrasting,
and reviewing to learn new vocabulary
2C – Learn new language heard in class
2H – Make inferences and predictions appropriate to grade-level
3D – Speak using grade-level content area vocabulary in context
4J – Use inferential skills such as predicting, making connections, drawing inferences, and
finding supporting text evidence
5B – Write using newly acquired basic vocabulary and content-based grade-level vocabulary
Resources
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District adopted textbooks and ancillaries.
Region IV Warm Up to Science TEKS-based Engagement Activities for Grade 8
Region IV TAKS Science Preparation Grade 8
Instructional Strategies (check those that apply)
X
X
X
Enhanced context strategies
Collaborative grouping strategies
Questioning strategies
Robert Marzano’s strategies
District strategies
Scientific investigations and reasoning (NOS,
X
X
descriptive and comparative investigations)
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X Inquiry strategies
X Manipulation strategies
X Assessment strategies
X Instructional technology strategies
Science Grade 8
Lab safety rules and procedures addressed
Appropriate modifications
Enhanced material strategies
X
Notes (procedures/5E model)
Engage: Activity/Warm-Up
1. Use bulletin board paper, a timer or a clock for the following activity.
2. Arrange students in cooperative teams and challenge them to write the list of ten words
in their journal as quickly as possible. The winner from each group will challenge the
teacher. (FYI - The teacher will write the abbreviations as fast as possible)
3. There are many forms of communicating such as texting, writing, and other forms of
communication.
1. PowerPoint
2. Texas
3. United States of America
4. Street
5. Drive
6. As Soon As Possible
7. Average
8. Organization
9. Laugh Out Loud
10. By The Way
4. Discuss with students the amount of time it took you to write each of the following
words and the importance of writing chemical formulas. ( Correct answers: ppt, TX.,
USA, St., Dr, ASAP, avg., org., lol, btw)
Explore: Field or laboratory investigation, mini-lab hands-on activity, construct a model, etc
1. Print chemical formula cards from the file CHEMICAL FORMULAS
MANIPULATIVE – HOUSEHOLD CHEMICALS (download from TRIAND).
2. Copy the two pages of cards on card stock and laminate before cutting apart.
3. Place each set in a baggie for each group.
4. Overview reasons scientists use chemical formulas instead of writing the chemical
names. Let students know the formulas they will be looking at are similar to the
chemical names.
5. Place students in cooperative teams.
6. Provide each group with a baggie of cards.
7. Ask students to spread out the cards with the black cards as the headers of the three
columns. Place all the common names under the COMMON NAME column then find
the matching chemical names and place it under the CHEMICAL NAME column.
Finally, the formula card that best matches the chemical name should be placed under
the FORMULA column.
8. Monitor students as they work and provide assistance as needed.
9. Once completed, call on students to read a common name, matching chemical name,
and matching formula. Make corrections as needed then call on a new student.
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Aldine I.S.D.
Science Grade 8
Explain: Student-Centered /Teacher Explanation/Student Analysis/Questioning/Note-taking
1. Read and prepare materials for the Explain activity in the Region IV TAKS Science
Preparation Grade 8 booklet pages 1119 – 124. This activity allows students to build
compounds and chemical equations while determining
the number of atoms in the reaction. (see picture to right)
2. Follow instructions provided in the activity.
3. See attached documents for notes. They can be placed on
the ELMO or written on the board for students to copy.
4. Provide students with a copy of Region IV Warm Up to
Science TEKS – based Engagement Activities for Grade
8 pages 111 and 113.
5. Discuss the answers and provide feedback.
Elaborate: Individual or Group Activity/Problem
Solving/Decision Making
1. Provide students with the worksheet titled COUNTING ATOMS with CHEMCIAL
EQUATIONS on the back. Each side has a brief description of the process of counting
atoms and looking at the reactants and products of a chemical equation. Although
students are NOT required to learn how to balance chemical equations in the 2009-2010
TEKS, they should be able to identify if the atoms are equal on both sides of the
equation. Students should be able to identify the reactants and the products of any
reaction provided.
2. Read through the description with students and the examples. Provide time for
independent practice.
3. Discuss the correct answers with appropriate feedback.
4. Provide students with a copy of Region IV TAKS Science Preparation Grade 8 pages
119-124 for independent practice. Teacher will determine if this practice is graded.
Evaluation: Closure, Performance Assessment/Journal entry, produce a product with a rubric
1. Provide students with a copy of the assessment titled STUDENT PAGE –
EVALUATION – CHEMICAL FORMULAS.
2. This is an independent practice activity that the teacher will grade and provide
appropriate feedback.
Materials (individual)
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Paper models for the EXPLAIN activity
Scissors
Journal
Bulletin board paper (per group)
Assorted markers
Timer or clock (teacher)
Vocabulary (define)
Chemical equation- The recipe that describes what you need to do to make a reaction take place.
Reactants- are the starting substances in a chemical reaction
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Aldine I.S.D.
Products- are the substances that are formed in a chemical reaction.
Science Grade 8
Chemical formulas – is a notation that shows the elements a compound contains and the ratio of the
atoms or ions of these elements in the compound.
Subscript – is a number, figure, symbol, or indicator that appears smaller than the normal line of
type and is set slightly below or above it subscripts appear at or below the baseline.
Coefficients- in science, a coefficient is the number in front of the chemical formulas. Also, the
coefficient indicates how many molecules take part in the reaction.
Daily Assessment
Provide students with the evaluation sheet where students will match the chemical formulas to
their names and explain why chemical formulas are important.
Homework Details
Write down 10 words or things you know the abbreviation. Explain why is it so important to
use and know abbreviations.
Homework Modifications
Follow IEP’s
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Aldine I.S.D.
Science Grade 8
Blackline
Masters
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Aldine I.S.D.
Science Grade 8
Notes for Chemical Formulas and Equations
 A formula tells the number and kinds of atoms in a molecule or compound.
 An oxygen molecule contains two oxygen atoms, so the formula for oxygen gas
O2.
 A carbon dioxide molecule contains one carbon atom and two oxygen atoms, so
the formula for carbon dioxide is CO2.
 Formulas and equations are used to describe a chemical reaction.
 For example, carbon reacts with oxygen to form carbon dioxide.
 This reaction equation with two sides.
 The reacting substances, or reactants, are shown on the left and the new
substances, or products, are shown on the right.
6H2O + 6CO2
Reactants

6O2 + C6H12O6
produce
Product
 In chemical reactions, atoms are neither created nor destroyed.
 The atoms of the reactants are simply rearranged into one or more new
substances.
 This means that the number and kind of atoms on the left number and kind of
atoms on the right side of the equations.
 Matter is conserved in all chemical reactions.
 Refer to pages 90-95 in the Glencoe textbook for additional clarifications.
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Aldine I.S.D.
Name:
Science Grade 8
Period:
Date:
Counting Atoms
Scientists use chemical formulas to simplify their communication with other scientists.
Elements in the Periodic Table are universal, meaning all chemists know H represents hydrogen,
H2O represents dihydrogen oxide or water. If a chemist had to write out every formula in every
equation, they would be writing a long time!
When working with chemical formulas and equations, it is important you understand the
parts. For example, carbon dioxide is composed of two different elements – carbon and oxygen.
Notice the prefix ‘di’ in front of the oxide. The prefix is very important when you are trying to write
chemical formulas. In this case, ‘di’ means 2 so there are 2 atoms of oxygen in the compound
carbon dioxide. There are a total of three atoms in the compound carbon dioxide – one carbon atom
and two oxygen atoms.
The formula for a compound indicates the elements that make up the compound and the
number of atoms of each element present in the compound. These numbers of atoms are indicated by
the use of small numbers called subscripts.
In the following examples, list each element in the compound and the number of atoms of
each element present. The first example has been done for you. You may already familiar with some
of the compounds. Try completing the table below. Use the examples to help you.
NAME
FORMULA
Limestone
CaCO3
Aspirin
C8H8O4
Moth Crystals
C6H4Cl2
Acetic Acid (Vinegar)
C2H4O2
Rust
ATOMS IN FORMULA
Ca = 1 atom of Calcium
C = 1 atom of Carbon
O = 3 atoms of Oxygen
C = 8 atoms of Carbon
H = 8 atoms of Hydrogen
O = 4 atoms of Oxygen
Fe2O3
Pyrite (Fool’s Gold)
FeS2
Sugar
C12H22O11
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TOTAL ATOMS
1 + 1 + 3 = 5 atoms
8 + 8 + 4 = 20 atoms
Aldine I.S.D.
Science Grade 8
Chemical Equations
Chemical formulas are used to communicate the reactants and products in a chemical reaction. For
example, plants use the light from the Sun to carry out the process of photosynthesis to produce their
food. Plants take in water and carbon dioxide from the atmosphere to produce oxygen and sugar.
Scientists would take a long time if they had to write out every chemical reaction they worked with
in the lab.
Chemical reactions are a lot like baking. If you are making a cake, the ingredients or
reactants are mixed and then baked. The product is the cake. If we wrote it as an equation, it might
look like this:
2 eggs + 1 cup water + 1/3 cup oil + 1 cake mix  1 cake
If we look at the equation for photosynthesis, we can use the element symbols to abbreviate
the actual element names. The equation would look like this:
6H2O + 6CO2

6O2 + C6H12O6
Reactants produce
6(2 + 1) + 6(1 + 2)
6(3) +
6(3)
18
+
18
=
=
36
=
= 36
Product
(6X2) + (6+12+6)
12 +
24
12 + 24
Notice the total number of atoms is equal on both the reactant and product side. If a
chemical equation is written properly, the total atoms will balance.
Complete the data table below by identifying the reactants and the products of each chemical
equation. Follow the example provided.
Cl2 + 2NaBr  2NaCl + Br2
Products
Reactants
2 Chlorine atoms
2 Chlorine atoms
2 Sodium atoms
2 Sodium atoms
2 Bromine atoms
2 Bromine atoms
This chemical equation has equal number of atoms on both sides of the equation so it is balanced.
H2O + Fe  Fe2O3 + H2
Products
Reactants
Is the equation balanced as written? Explain.
Na2O + CO2  Na2CO3
Products
Reactants
Is the equation balanced as written? Explain.
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Aldine I.S.D.
Science Grade 8
Name _______________________________________ Period____ Date ___________________
Student Page – Evaluation
Chemical Formulas Assessment
Matching: Select the correct name that represents the chemical formula to the left.
1. _____ NaCl
a. Magnesium Chloride
b. Sodium Chloride
c. Potassium Bromide
d. Sodium Sulfate
e. Carbon Dioxide
f. Potassium Hydroxide
g. Calcium Hydroxide
h. Ammonium Cyanide
i. Iron Oxide
j. Dihydrogen oxide
k. Lithium Chloride
l. Calcium Sulfid
2._____ KBr
3.______ CO2
4.______ Na2SO 4
5._____ Fe2O3
6._____ KOH
7. _____ Ca OH
8. _____ MgCl2
9.______ H2O
10. Explain why it is important for scientists to use chemical formulas or equations in science.
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Aldine I.S.D.
Science Grade 8
ANSWER KEY
Teacher Page – Evaluation
Chemical Formulas Assessment
Matching: Select the correct name that represents the chemical formula to the left.
1. ___B__ NaCl
a. Magnesium Chloride
b. Sodium Chloride
c. Potassium Bromide
d. Sodium Sulfate
e. Carbon Dioxide
f. Potassium Hydroxide
g. Calcium Hydroxide
h. Ammonium Cyanide
i. Iron Oxide
j. Dihydrogen oxide
k. Lithium Chloride
l. Calcium Sulfid
2.__C___ KBr
3.___E___ CO2
4.___D___ Na2SO 4
5.___I__ Fe2O3
6.___F__ KOH
7. __G___ Ca OH
8. ___A__ MgCl2
9.___J___ H2O
10. Explain why it is important for scientists to use chemical formulas or equations in science.
Scientists use chemical formulas to minimize the amount of work and time spent on writing
out the whole chemical names. The Periodic Table is universal and scientists around the
world are able to write a symbol and everyone knows what is meant. Writing chemical
formulas are easily broken down by scientists and communicated easily.
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