Transcript 8th Grade Chemistry Focus Activities

Chemistry Focus Activities
Chemical Formulas & Equations
8th Grade
The focus activities in this presentation are intended to provide students
opportunities to:
 interpret and analyze graphs
 explain their reasoning when choosing an answer
in multiple choice questions.
Teacher Instructions
• Choose from the focus activities provided and use as needed.
Examples:
 Segment the graphs and questions and use them individually or in pairs for warm-ups
and exit tickets.
 Incorporate the items as a group or individually into intervention strategies.
 Methodically work through answers with students in support of building test
taking/processing skills and assessing their logic (metacognition).
 Follow-up questions could be used as prompts for journal entries.
• Provide students opportunities to discuss their answers with their peers.







Round Robin (write/share/add-on/pass)
Rally Table (write/share/revise)
Quiz-Quiz-Trade
Numbered Heads Together (write/share/discuss/consolidate/represent)
A-B Pair Share
Shoulder Partner
(think/pair/share)
Stand Up/Hand Up/Pair Up
• Provide the STAAR Grade 8 Science Reference Materials (Formulas and
Periodic Table of the Elements) as an anchor of support.
Chemical Formulas (8.5F)
•
8.5: Matter and energy. The student knows that matter is composed of atoms and has
chemical and physical properties. The student is expected to:
8.5F: recognize whether a chemical equation containing coefficients is balanced or not
and how that relates to the law of conservation of mass.
•
Review
6.5A: know that an element is a pure substance represented by chemical symbols.
6.5C: differentiate between elements and compounds on the most basic level.
7.6A: identify that organic compounds contain carbon and other elements such as
hydrogen, oxygen, phosphorus, nitrogen, or sulfur.
8.5D: recognize that chemical formulas are used to identify substances and determine the
number of atoms of each element in chemical formulas containing subscripts.
8.5E: investigate how evidence of chemical reactions indicate that new substances with
different properties are formed.
•
Skills TEKS: 8.2C-E
Interpreting Graphs
Focus Activities
Part I: Components of a Graph
1. What type of graph is
represented?
2. Label the x-axis with an “X”
and the y-axis with a “Y”.
3. What information is provided
on the x-axis?
4. What information is provided
on the y-axis?
5. Which axis represents the
independent variable? What was
the independent variable for this
experiment?
6. Which axis represents the
dependent variable? What was
the dependent variable for this
experiment?
7. What trends do you notice on
the graph?
8. Create a table from the
information in the graph.
Part II: Analyzing the Graph
1. How does the volume of CO2
change over time?
2. How long does the reaction
take?
3. During the reaction, when does
the maximum amount of CO2
produced?
4. How long does it take to
produce 100 cm3 of CO2 during
the reaction?
5. What is the difference in
volume of CO2 between 200
seconds and 1200 seconds?
Follow Up Discussion Questions
1. Is the chemical equation for this reaction
balanced?
2. What evidence supports your position?
Justify Your Answer
Focus Activities
1. Students read the question and select the correct answer.
2. Students write a statement for each answer selection stating why it is correct or incorrect.
3. Students choose the correct answer choice based on their analysis of each answer selection.
Review (6.5A): Use your periodic table as a resource. What is the
elemental symbol for sodium?
Answer Choice
A. S
B. Na
C. 11
D. N
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Review (6.5C): Why is carbon considered to be an element, but
carbon dioxide is classified as a compound?
Answer Choice
A. Carbon dioxide is a gas.
B. Carbon dioxide has two different
elements.
C. Carbon is found in living matter.
D. People exhale carbon dioxide.
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Review (7.6A): Look at the table provided. Which of the following
compounds belongs in the Y Compounds column in the table?
Answer Choice
A. Fe2O3
B. CH3COOH
C. C15H31CO2C30H61
D. C8H10N4O2
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Review (8.5D): (NH4)2CO3
How many atoms of hydrogen (H) are found in this substance?
Answer Choice
A. 2
B. 4
C. 6
D. 8
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Review (8.5D):
What is the best formula for the above substance?
Answer Choice
A. H2 and O2
B. H2O2
C. H2O
D. H2O2
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Review (8.5E): Students perform an experiment in which a crystalline
substance is added to a beaker filled with water. The crystals dissolve, and a
precipitate is formed. The bottom of the beaker feels warm to the touch. The
temperature is monitored and the temperature data is recorded. Which
observation in the above experiment tells you that a chemical reaction has
occurred?
Answer Choice
A. A decrease in temperature
B. The crystals dissolve.
C. A gas is produced.
D. The formation of a precipitate
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Review (8.5E): A crystalline substance is
added to a beaker filled with water. The
crystals dissolve, and a precipitate is
formed. The bottom of the beaker is too
hot to touch. The temperature is
monitored and the temperature data is
shown on the graph below.
At which time did the temperature first
reach 65ºC?
Answer Choice
A. 40
B. 48
C. 72
D. 80
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
A student writes the following chemical equation. Did the
student write a balanced equation?
Na2SO4 +
Answer Choice
Yes
No
K2Cl
e Na2Cl +
K2SO4
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Follow Up Discussion Questions
1. What strategy did you use to determine if the
chemical equation was balanced?
2. Why must a chemical equation be balanced?
3. Which law defines this explanation?
Complete an atom “inventory” to decide if the following
chemical equation is balanced.
Sn +
Answer Choice
Yes
No
HF e SnF2
+
H2
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Follow Up Discussion Questions
• Describe what occurs during a chemical reaction and how this
process can be visualized by writing a chemical equation. In
your description, include answers to these questions.
– What are the reactants, and what occurs to them?
– What are the products, and what occurs to them?
– Why is it important that the chemical equation be
balanced?
– What must be equal in a balanced equation?
Complete an atom “inventory” to decide if the following
chemical equation is balanced.
SiO2
Answer Choice
Yes
No
+
C e SiC +
CO
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Complete an atom “inventory” to decide if the following
chemical equation is balanced.
Al(OH)3
Answer Choice
Yes
No
+
3HCl
e AlCl3
+
3H2O
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Which number could replace the “?” to balance this equation.
H2 +
Cl2 e ?HCl
Answer Choice
A. 1
B. 2
C. 3
D. 4
Justify why each answer is either correct or
incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect) because…
Follow Up Discussion Questions
1. How many atoms of each element are in the
reactants?
2. How did you know?
3. What part of the chemical equation tells you
the number of atoms in the reactants?
4. What is the “?” in the products called?
Which of the following is true about the Law of Conservation of
Mass?
Answer Choice
A. Matter must first be destroyed in order
to be created.
B. The mass of the products is always less
than the mass of the reactants.
C. The mass of the reactants must always
equal the mass of the products.
D. The mass of the products is always
greater than the mass of the reactants.
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Follow Up Discussion Questions
1. In your own words, define the Law of
Conservation of Mass. Make sure to relate
the Law of Conservation of Mass to these
terms: subscripts, coefficients, products, and
reactants.
Is the Law of Conservation of Mass conserved in this
reaction?
2H2O → 2H2 + O2
Answer Choice
A. Yes, because the number of atoms of
each element on both sides of the
equation has not changed.
B. No, the number of molecules must be
the same on both sides of the chemical
equation.
C. No, this chemical reaction is not
possible.
D. Yes, because the mass of the products
is always greater than the mass of the
reactants.
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Look at the following four chemical equations. Choose
the correctly balanced chemical equation.
Answer Choice
A. 2HClO → 2H2O + 2Cl2O
B. CuO + 2HCl → 2CuCl2 + H2O
C. MgCl2 + NaF → MgF2 + NaCl
D. 2C2H2 + 5O2 → 4CO2 + 2H2O
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
With respect to the Law of Conservation of Mass, what
is the most accurate way to describe what happens to
the atoms involved in a chemical reaction?
Answer Choice
A. The reactant atoms are destroyed, and
new product atoms are formed.
B. The reactant atoms are rearranged to
form new compounds called the products.
C. Nothing happens to the atoms during
the reaction.
D. Additional atoms are required in order
to make the products.
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Which equation best obeys the Law of Conservation of
Mass?
Answer Choice
A. N2 + 3H2 --> 2NH3
B. H2 + O2 --> 2H2O
C. 2Ag2O --> Ag2 + O2
D. N2 + H2 --> NH3
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
What is wrong with the chemical equation shown
below?
CH4 + O2
--> CO2 + H2O
Answer Choice
A. It is not balanced. It follows the Law of
Conservation of Mass.
B. It is not balanced. It does not follow the
Law of Conservation of Mass.
C. It is a balanced equation. There is
nothing wrong with it.
D. It is a balanced equation. It follows the
Law of Conservation of Mass.
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…
Which equation below is correctly balanced?
Answer Choice
A. C12H22O11 + 12O2 --> 6CO2 + 11H2O
B. 2C12H22O11 + 12O2 --> 24CO2 + 11H2O
C. C12H22O11 + 12O2 --> 12CO2 + 22H2O
D. C12H22O11 + 12O2 --> 12CO2 + 11H2O
Justify why each answer is either correct
or incorrect by drawing or writing a clear
statement to show your reasoning.
This answer choice is (correct/incorrect)
because…