Factors Affecting Rates of Reactions:Nature of Reactants and Surface Area

I. ObjectivesAt the end of the lesson, the students should be able to:

1. Demonstrate the effects of changing factors in the rate of chemical reactions

2. Explain the factors affecting reaction rates in terms of the collision theory

3. Recognize the value of these different factors by citing their applications in given situations.

II. Subject MatterA. Topic: Factors Affecting Rates of Reactions: Nature of Reactants and

Surface Area1. Collision theory

- states that for a reaction to occur, particles must collide in the right orientation and with sufficient energy

2. Factors Affecting Rates of Chemical Reactionsa. Nature of Reactants

- the nature (composition, properties, phase) of the reactants involved in a reaction

b. Surface Area- size of the reacting substances, i.e., for the same amount

of reactant, smaller particle size means greater surface area

B. References:Bureau of Secondary Education. (n.d.). Module 17: Reaction

Rates and Equilibrium.Chang, R. (2010). Chemistry. (10th ed). USA: Mc-Graw Hill.Harned, Slatoff, & Stanchock. (n.d.). Mentos Investigation.

Retrieved from http://www.eastpennsd.org/teacherpages/nstanchock/downloads/Mentos%20Investigation.doc

Royal Society of Chemistry. (n.d.). The Mentos Explosion. Retrieved from http://www.rsc.org/images/The_Mentos_explosion_tcm18-194232.pdf

Spangler, S. (n.d.). Mentos Diet Coke Geyser. Retrieved from Steve Spangler Science: http://www.stevespanglerscience.com/lab/experiments/original-mentos-diet-coke-geyser

C. Strategy: Problem-Based Learning (Guided discovery approach)Students work in small groups to research and pose solutions to

problems, both a collaborative and multifaceted environment is

created. Within this environment, students can explore multiple solutions and best practices for tackling projects.

D. Vocabulary:1. Reactants – chemical substances involved in a reaction2. Nature of reactant – qualities of a reactant (e.g. phase,

composition, properties), which can affect the rate of a reaction 3. Surface area – total area covered by the surface of an object; how

much surface is exposed for reaction E. Skills Development / Values Integration:

1. Time/resource management2. Communication and collaboration3. Leadership and responsibility4. Critical thinking and problem solving5. Information literacy (graphing and presentation of data)6. Social responsibility and accountability

F. Integration with Other Subject Areas:1. Mathematics – the activity requires the students to evaluate,

analyze, and summarize data they collected.2. Language arts – each group must be able to communicate their

ideas effectively and efficiently to convince ‘the DOST’ to select them for a full-scale test.

G. Materials:1. For presentation:

- Projector- Laptop

2. For activity (per group):- Mentos-Coke Explosion activity sheet- KWLH chart- 1 roll each of mint- and fruit-flavored Mentos candies- 500mL each of regular Coke and Coke Zero- 2 x 100mL graduated cylinder

H. Time Frame: 240 minutes

Activity Time Target SkillsScience

ConceptsDAY 1

Pre-lab & PlanningReport of Plan

40 min.20 min.

Communication and collaborationTime/resource management Collision Theory

Factors Affecting Reaction Rates: Nature of Reactants and Particle Size

DAY 2Testing 60 min. Leadership and responsibility

DAY 3Write-upFinal ReportPost-lab

20 min.30 min.10 min.

Information literacy

DAY 4

DiscussionApplicationValuing

25 min.25 min.10 min.

Critical thinking and problem solvingSocial responsibility and accountability

TOTAL 240 min.

III. ProcedureA. Routine

1. Greeting2. Prayer3. Attendance

B. MotivationThe teacher presents a video of a YouTube clip (Mentos and Diet

Coke Experiments). The Mentos and soda fountain will play an important part of the student’s next activity. This serves to prepare them for that.

C. Lesson Proper1. PROBLEM: Coke-Mentos Explosion

The teacher has the students feel under their armrests for their group assignments. He has them seat with their group mates and presents the problem:

As a highly regarded chemist at the University of ___________, you are one of four researchers awarded with a multi-hundred peso research grant to investigate a phenomenon that has puzzled scientists from all over the globe: The Coke-Mentos Explosion. You will have to present your team's findings to the Department of Science and Technology. The team that convinces their colleagues and the DOST shall do a full scale test. Success depends on presentation of data and the ability to answer questions of the Department. Will it be your team that solves the case?

Each group must have:1. a Chemist to take charge of executing the experiment

and presenting findings to the DOST2. a Research Assistant to assist the chemist in executing

the plan3. a Lab Journalist to record the team’s data and prepare a

report to present to the DOST4. at least one Custodian to claim supplies form the DOST

and maintain order in/of the work areaPhases:

DAY 11. Pre-lab & Planning (40 min)2. Report of Plan (20 min)

The teacher allows time for students to answer the KWLH sheet (Know, Want columns). Each group shall present their plans. Groups shall rate each other (Colleague Evaluation Checklist) during presentation, the teacher shall do the same.DAY 23. Testing (60 min)

The teacher uses a checklist to assess each group’s performance. The day’s assignment is to gather information of the Mentos-Coke experiment for the final report.DAY 34. Write-up (20 min)5. Presentation of Findings (30 min)6. Post-lab & full-scale test (10 min)

Each group shall present their findings and conclusions. Groups shall rate each other during presentation, the teacher shall do the same. The teacher shall ask questions relating to their data.

2. DISCUSSION: Collision Theory & 2 Factors Affecting Reaction RatesDAY 4

The teacher gathers responses from the class stating their explanations for the results of the experiment. The teacher goes on to explain that the results of the experiment can be better explained by the Collision theory.

After giving a brief explanation, he goes into detail on 2 factors affecting chemical reactions as consequences of the Collision theory.

The teacher goes back to the results of the experiment. He explains the process behind the formation of bubbles in Coke.

Questions:- Look at the ingredients of regular Coke and Coke Zero.

What ingredient was different? Did this affect the eruption height? How do you think this difference could have affected the results? (Nature of Reactants)

- Fruit-flavored Mentos candies have a carnauba wax coating. Explain, using the collision theory, how this could make a difference in the rate of gas formation. (Nature of Reactants)

- Which has a greater surface area: a sugar cube or powdered sugar of the same mass? Which of them will burn faster? (Particle Size)

D. GeneralizationThe teacher writes important terms of the lesson on the board

(Collision theory, Reaction Rate, Nature of reactants, Particle size)

and calls on a few students to use these terms to summarize the lesson. Students are given time to answer the KWLH sheet (remaining sections)

E. ApplicationThe teacher asks a representative of each group to pick one of 4

folded cards. On the cover of each card is a different picture, corresponding to the theme of the questions. Inside the card is a question, which the students must answer using their knowledge of the factors affecting reaction rates. Questions are worth 5 points.

Example:- “Alkali metals are usually stored as big lumps of metal in

glass containers filled with kerosene. What could be the reason/s behind this procedure?”

- “Analogies are a great way to improve understanding. Imagine you and your friends in Divisoria, where to bump someone can cost you a watch or a necklace. By applying the concepts you learned today, how can you DECREASE the likelihood of a theft happening to you?”

- In the movies, people make cars explode by igniting the fuel tank (filled with liquid gasoline). This is not possible outside of Hollywood. A leaking gas stove however, is a different story. Explain the difference.

- During the dry season, flour mills face a constant threat of dust explosion, not from the sacks of flour, but the flour dust. The same danger exists in lumber mills, due to sawdust. What factors could possibly contribute to this threat?

F. Valuing: Social Responsibility and AccountabilityThe teacher poses this situation to the class:

Tetraethyl lead is a fuel additive used to control the premature combustion of fuel inside an internal combustion engine. This reduces the ‘knocking’ that causes inefficient combustion of fuel, thus the term anti-knocking agent.

Recent reports however reveal that tetraethyl lead can cause acute or chronic lead poisoning if inhaled or absorbed through the skin. In addition to this, its products are detrimental to catalytic converters used to nullify other substances in exhaust.

Consider yourself in the following situations:(a) You are the chief manufacturer of this additive who

just now understood the health risk. What can you do?(b) You are an average citizen with knowledge of the risks

of tetraethyl lead. What can you do?

IV. AssignmentThe teacher gives the assignment to prepare the class for the

next discussion: 3 more factors affecting rates of chemical reactions. The teacher gives instructions to answer the questions in the students’ science notebook.

- Why does food cook faster using a pressure cooker than it does using other means?

- Hydrogen peroxide bubbles vigorously when you apply it on a wound. What causes this reaction?