chemistry focus activities chemical formulas & equations 8 th grade the focus activities in this...

Chemistry Focus Activities

Chemical Formulas & Equations8th 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 ShareShoulder 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.

• Review6.5A: 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

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 I: Components of a 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?

Part II: Analyzing the Graph

Follow Up Discussion Questions

1. Is the chemical equation for this reaction balanced?

2. What evidence supports your position?

Justify Your Answer

Focus Activities1. 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 ChoiceJustify why each answer is either correct or incorrect by drawing or writing a clear

statement to show your reasoning.

A. S This answer choice is (correct/incorrect) because…

B. Na

C. 11

D. N

Review (6.5C): Why is carbon considered to be an element, but carbon dioxide is classified as a compound?



A. Carbon dioxide is a gas. This answer choice is (correct/incorrect) because…

B. Carbon dioxide has two different elements.

C. Carbon is found in living matter.

D. People exhale carbon dioxide.

Review (7.6A): Look at the table provided. Which of the following compounds belongs in the Y Compounds column in the table?



A. Fe2O3This answer choice is (correct/incorrect) because…

B. CH3COOH

C. C15H31CO2C30H61

D. C8H10N4O2

Review (8.5D): (NH4)2CO3

How many atoms of hydrogen (H) are found in this substance?



A. 2 This answer choice is (correct/incorrect) because…

B. 4

C. 6

D. 8

Review (8.5D):

What is the best formula for the above substance?



A. H2 and O2This answer choice is (correct/incorrect) because…

B. H2O2

C. H2O

D. H2O2

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?



A. A decrease in temperature This answer choice is (correct/incorrect) because…

B. The crystals dissolve.

C. A gas is produced.

D. The formation of a precipitate

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?




B. 48

C. 72

D. 80

A student writes the following chemical equation. Did the student write a balanced equation?

Na2SO4 + K2Cl Na2Cl + K2SO4



Yes This answer choice is (correct/incorrect) because…

No


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 + HF SnF2 + H2




No


• 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?


SiO2 + C SiC + CO




No


Al(OH)3 + 3HCl AlCl3 + 3H2O




No

Which number could replace the “?” to balance this equation.

H2 + Cl2 ?HCl

Answer ChoiceJustify why each answer is either correct or

incorrect by drawing or writing a clear statement to show your reasoning.


B. 2

C. 3

D. 4


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?



A. Matter must first be destroyed in order to be created.

This answer choice is (correct/incorrect) because…

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.


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



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.

Look at the following four chemical equations. Choose the correctly balanced chemical equation.



A. 2HClO → 2H2O + 2Cl2OThis answer choice is (correct/incorrect) because…

B. CuO + 2HCl → 2CuCl2 + H2O

C. MgCl2 + NaF → MgF2 + NaCl

D. 2C2H2 + 5O2 → 4CO2 + 2H2O

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?



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.

Which equation best obeys the Law of Conservation of Mass?



A. N2 + 3H2 --> 2NH3This answer choice is (correct/incorrect) because…

B. H2 + O2 --> 2H2O

C. 2Ag2O --> Ag2 + O2

D. N2 + H2 --> NH3

What is wrong with the chemical equation shown below?CH4 + O2 --> CO2 + H2O



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.

Which equation below is correctly balanced?



A. C12H22O11 + 12O2 --> 6CO2 + 11H2OThis answer choice is (correct/incorrect) because…

B. 2C12H22O11 + 12O2 --> 24CO2 + 11H2O

C. C12H22O11 + 12O2 --> 12CO2 + 22H2O

D. C12H22O11 + 12O2 --> 12CO2 + 11H2O

chemistry focus activities chemical formulas & equations 8 th grade the focus activities in this...

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