Constructivist Planning of a Chemistry Lesson – Acid and Base

Title of lesson: Acids and Bases

Level: 3^rd year Chemistry

Lesson plan:

I. Goals

The student will be able to:

• Define the terms acid and base
• Explain what makes an acid/base strong or weak
• Calculate the pH or pOH for a given system
• Calculate acid or base concentrations based on titration data

II. Overview

Acids and bases are an important part of our day-to-day lives. The term acid rain comes up frequently when discussing environmental concerns. Acids are defined as being electron pair acceptors, frequently meaning that they donate an H₃O⁺ ion. A base is defined as being an electron pair donor, frequently meaning that they accept H₃O⁺ or donate OH^-. pH is defined as being the negative log of the hydrogen ion concentration [H₃O⁺]. pOH is defined as being the negative log of the hydroxide ion concentration of the solution [OH^-]. The product of the [H₃O⁺] and [OH^-] concentrations is the K_w=1.0 x 10^-14. The more an acid or base dissociates in an aqueous solution, the stronger it is considered to be. For example, HCl is considered to be a strong acid, and NaOH is considered to be a strong base.

Students will be investigating acids and bases using pH tests, titrations, class discussions, lecture and reading.

III. Resources, materials and supplies needed

• pH testing equipment

litmus paper

colorimetric indicators

pH probes and CBLs - one per group of students

• Textbook or other resource with course level appropriate information on acids and bases.

• Burets ­ one per group of students

• Erlenmeyer flasks - two per group of students

• Colorimetric indicators or pH probes and CBLs ­ one dropper bottle of indicator per group, or one pH probe and CBL per group of students

• Standard acid and base solutions (known concentrations) 0.5 M HCl and NaOH solutions 75 ml of each per group of students

• Unknown acid and base solutions 0.75 or 1M concentrations of HCl and NaOH solutions 15 ml of each per group of students

• Titration curves for strong, weak, and polyprotic acids, titrated with a base.

Engagement

Student behaviors / activities:

Using litmus paper, pH indicators, and/or pH probes determine the pH for various household chemicals, tap water (especially in Austin, the water is quite basic), and deionized water.

Answer questions of why this relates to acids and bases.

Create a concept map about acids and bases.

Brainstorm what makes acids and bases strong or weak.

Predict where household products (bleach, vinegar, solution of baking soda, carbonated beverages) would fall on the pH scale.

Teacher behaviors / activities:

Demonstrate technique for using various testing methods.

Observe students while they are performing the experiments. Answer any questions. Make sure students follow lab safety rules.

Facilitate discussions of acids and bases.

Clarify misconceptions about acids and bases.Ask students why two samples of water have a different pH.

Draw pH scale on board.

Ask how the pH of something can be changed.

.

Exploration

Student behaviors / activities:

Experiment with pH by measuring the pH of water before and after adding a drop of acid or base to it.

Graph the relationship between the amount of acid/base added to the pH.

Look at titration curves of strong acids with strong bases, weak bases, and the titration curves of polyprotic acids.

Teacher behaviors / activities:

Monitor students while doing the experiment.

Compile data on the board.

Answer any student questions. Ask students to compare the graphs they generated with the titration curves. How are they related?

Explanation

Student behaviors / activities:

Discuss findings from the exploration.

Hypothesize the relationship between the graphs generated to titration curves.

Discuss how pH relates to acid/ base concentration.

Read about acids/bases and discuss as a class their misconceptions before the reading.

Ask questions.

Teacher behaviors / activities:

Present information on what defines an acid or a base. Discuss what makes an acid/base strong or weak. Relate this concept to solubility.

Explain pH/pOH scale, and how pH/pOH is determined ([H₃O⁺] ion concentration and [OH^-] ion concentration).

Demonstrate pH/pOH calculations.

Review basic log rules.

Elaboration

Student behaviors / activities:

Titrate a strong acid solution with a base. Titrate a strong base with an acid. Determine the concentrations of these solutions.

Teacher behaviors / activities:

Discuss neutralization reactions.

Explain titrations and why they are used.

Demonstrate titration technique.

Demonstrate titration calculations.

Evaluation

Student behaviors / activities:

Generate a basic lab report about the titration experiment.

As a class discuss the findings of the comparisons of titration curves.

Take a quiz about acids and bases, where they must identify something as being an acid or base, determine the pH of a solution, and determine the concentration of an acid or base solution from titration data.

Teacher behaviors / activities:

Facilitate class discussion, and help the students relate titration curves, and the titration process to the topic of acids and bases in general.

Ø Reflection: what was the most difficult aspect of planning? How is planning a constructivist activity different from other types of lesson?

Planning allows teachers to personalize the curriculum and allows them to anticipate instructional needs in advance so materials can be gathered and organized. It provides a script that directs interactions with students and provides a form of psychological or emotional security which reduces the normal anxiety associated with teachers. But planning a constructivist activity is different from other types of lesson and presents some difficulties. It needs much more time to search and think about many types of questions that involve students and lead them to reach the right answers and to achieve the goal of the lesson. Furthermore, these different types of questions should fulfill the hierarchical different levels in the Bloom’s Taxonomy (cognitive domain). In addition, Teacher-learning contexts change and teachers' behavior must change accordingly. The basic problem for teachers is, therefore, to acknowledge that there is no one best way to behave, and then to learn to make decisions in such ways that their behaviors are continually appropriate to the dynamic, moment to moment complexity of the classroom. Thinking and preparing activities that motivate and involve students in a way to lead them to construct their own understanding is not easy at all. It needs lots of materials other than just a textbook to prepare such sort of activities and concrete examples. One needs to prepare graphs, pictures and many others such as the ones listed above in my lesson plan, in order to illustrate clearly the content of the lesson. Finally, the teacher should find a way to know if they students understand the material and their role and the most important thing is that they reach the goal of the lesson.

Interview a teacher about the rules and procedures in his or her classroom.

I’m willing to teach chemistry for the secondary classes, for this reason I have chosen to interview a scientific teacher who instruts adults:

Ø School’s Name : Modern Community School (MCS)

Ø Location : Ain el Remmeneh

Ø Teacher’s Name : Michella Bou Eid

(coordinator & a mathematical teacher of grade 11 & grade 12)

1. What are they?

· Arrival on time

· low rate of absences

· Getting permission to communicate any type of questions

· Handing assignments on time...

2. How are they communicated to students?

They are written on a sheet presented to the students at the beginning of the year or sometimes they are communicated orally.

3. How should you manage a class at the beginning of the year?

Mainly communicate the rules.

Specify the different consequences in case of any misbehavior.

4. What are the consequences for breaking or following the rules?

Following the rules is a must so no extra credit is given for that.

As for breaking the rules the consequence depends on the situation.

5. What are the biggest problem areas?

None, everything could be viewed as minor.

6. Which systems should you adopt for handling disruptions?

Depending on the type of disruption. It Could be a verbal warning or taking out credits or placing a student out of the class, ...

7. Do you prefer to interact with a small group of students or a big one? Why?

One could be more helpful with a small group because more individual time is given to each student but dealing with a large group is a challenge one should be ready to take.

8. How can you deal with individual problems?

Discuss them outside the class. The solution depends on whether they are educational or personal. In the educational case an extra help could be provided to the student. In the personal case, one should mainly try to simplify the problem indicating that there is a solution to everything.

9. In case of too much noise in class, what would you do?

One should avoid getting to that point by giving individual comments, or punishments to the first one who says a word avoiding further noise, but in case things got out of control:

One should stop saying any word for a short while trying to face the students with a great deal of outer seriousness till they calm down.

The worst strategy is to raise ones voice.

10. If someone argue while you want to seat him, what would you do?

Display his options. He either sits in the assigned place or face a consequence you need not argue with him.

Conclusion:

After this conversation with mrs. Michella, I can say that she is authoritative with her student, which is, in my opinion, the right way to deal with them. We can see from her answers that she is firm and very consistent according to the rules and procedures in her classroom, and, at the same time, she is friendly and caring by giving her students an extra help when they need it, or by trying to simplify the problems they are facing.

After interviewing mrs. Michella, and while typing this assignment, I remembered a case that had happened with my general chemistry doctor, in the Lebanese university, and I wish I could have the second chance to ask this teacher two more questions. Since I could not reach her any more, I would like to ask you these two questions:

1- it is the first day of class, you are writing something on the board and a paper wad hits you in the back, what would you do?

2- how do you encourage students to learn ? can a student be forced to learn?

Student teacher Portfolio

Date : 25/3/2008

Grade : grade 9

Instructor: Rita Breidy

Course : Chemistry

Unit : unit 4 – Organic Chemistry

Topic : Esterification

Content : the ester is a family of organic substances. It is produced by the

esterification reaction, which is a combination between an alcohol

and an organic acid.

Goals : students will be able to:

1. know the structural formula of a primary alcohol

2. know the structural formula of a carboxylic acid

3. compare between an organic acid and a mineral acid

4. understand the definition of the esterification reaction

5. compare between the “Esterification” and the “hydrolyze” reaction

Objectives: After completing this section, the students will state the functional

group of each product (alcohol and acid), and will give its name.

they will identify and write the equation of the esterification reaction

with complete accuracy.

Materials : Chemistry Textbook, Pictures, Worksheets.

Introduction: Chapter 2: Section 2.1 & 2.2 Thinking Critically. Introduce New

Science Terms to students through the use of different molecular

models. Students will listen to the explanation of the teacher.

Teacher will encourage the students to use thinking skills in

discussion and questioning.

Development: Teacher will transfer the molecular models into developed formula

on the blackboard. Students will observe, compare, and discuss

the different formulas to understand the characteristics of the

esterification reaction.

Practice : Students will work in pairs to practice identification of alcohol and

acid, of organic and mineral acids, of esterification and hydrolyze,

using their textbook.

Conclusion:

After planning this lesson, I asked Mrs. Antoinette Abi Nader, a chemistry teacher and a coordinator at Besançon school-Baabda, to critique my work. After reading it, she said that it is a good job, and that I have listed the major procedures which have to be mentioned in a lesson plan, continuing that I can add the prerequisites of this lesson (such as, students must know the aliphatic hydrocarbon). Moreover, she said that I can inform them also, at the end of this lesson, about the lesson that might follow as a result of this one, such as, the “Saponification = Ester + Base”.

According to me, this is the first time that I plan a lesson. I have tried to use the different procedures mentioned in the second chapter of this course “Teaching Planning” as a guide. This experience taught me how to organize my ideas and my knowledge, and how to introduce them to my students in a simple way. Furthermore, I have been guided that I should remember my students at the beginning of a class about the prerequisites before introducing a new topic, in a different way; I should link my new lesson to the previous one.

Running head: increasing learning through student involvement

I have chosen to teach a chemistry lesson for the grade 10 (first secondary year). I am going to explain “the solubility of gases in water” which is a unit in the chapter five: “WATER”.

The objective of this unit is to make students recognize the effect of temperature on solubility. This part from the lesson is important for students. It will benefit them. They need to understand the factors affecting solubility so they can accurately grasp the definition and the expression of solubility.

Lesson:

-What about the solubility of Gases?

The maximum amount of solute in grams that dissolves in 1liter of water to make a saturated solution at a given temperature is known as the SOLUBILITY of the solute.

The Solute can be: a solid, a liquid, a gas.Most often we think of solutes as solids. In this lesson we will focus on solutes that are gases.

-A SATURATED solution is one in which no more solute can dissolve.

The SOLUBILITY measures the concentration of a saturated solution.

-Carbon dioxide has a solubility of 1.8 g/L at 20⁰C. This means that 1.8 grams of carbon dioxide will dissolve in 1L of water to make a saturated solution at 20⁰C. No more than 1.8g of carbon dioxide can dissolve in the liter of water as long as the temperature remains constant at 20⁰C.

-In this lesson you will examine the effect of temperature on the solubility of a typical gas which is: CARBON DIOXIDE.

Using the power point as a technology to involve students and to reserve time, I will explain the definition of the solubility. Then I will state the different types of a solute mentioning that in this lesson we will focus on solutes that are gases. Moreover, I will link a previous knowledge which is the saturated solution to the new lesson: Solubility.

Finally, I will give an example of a typical gas which is the carbon dioxide. This typical gas will be used through an activity to involve my students. This activity is followed by an assignment (ten questions) that students have to do in class. These ten questions will involve students by helping them to think, analyze, and discover the effect of temperature on solubility. After each question, students will have enough time to discuss with each other and write their answer which is going to be corrected, through the power point program, in case of a misunderstanding.

At the end of the session, I will summarize the lesson by reminding the students about the definition of solubility and by listing the different criteria and factors related to the solubility of gases. In addition, I will ask them to give their opinion and what did they feel about this activity and the way I have presented it to them. (Affective domain)

Activity:

We are going to do several taste tests on a carbonated beverage which is: PEPSI

Materials:

• 3 canes of Pepsi (at different temperature)

• 3 small plastic cups

• Sample 1: Pepsi that has been in the fridge for at least one day

• Sample 2: Pepsi left at room temperature for few hours (2h)

• Sample 3: Pepsi exposed to the sun for few hours (2h)

You have to:

• Place your tongue in each solution to test for the degree of fizzing on your tongue.

• Then taste each sample. Record the amount of fizz in each sample.

• If you are uncertain which sample has the least fizz, repeat your tongue test and your taste test in reserve order. Be sure to record your results.

• Compare your fizz taste test results with one other classmate. If you find different results between the two of you, then try to find a reason for the difference. Repeat the experiment to see if your results can agree.

Assignment:

Put a paper on your desk and write on it the number of the question followed by the right answer

1- Which sample has the lowest temperature?

• Sample 1

• Sample 2

• Sample 3

2- Which sample had the highest temperature?

• Sample 1

• Sample 2

• Sample 3

3- Which sample had the most “fizz”?

• Sample 1

• Sample 2

• Sample 3

4- Which sample had the least “fizz”?

• Sample 1

• Sample 2

• Sample 3

5- What causes the “fizz” in beverages?

6- Carbon dioxide acts like a typical gas. What happens to the solubility of carbon dioxide gas as the temperature increases?

• The solubility increases as the temperature increases

• The solubility decreases as the temperature increases

• The solubility does not change as the temperature increases

7- Is the solubility of carbon dioxide gas greater at high temperatures or at lower temperatures?

• Higher

• lower

8- When does more gas stay dissolved, at higher temperature or at lower temperature?

• More gas will dissolve when the temperature is lower

• More gas will dissolve when the temperature is higher

9- Oxygen also acts like a typical gas. What happens to the solubility of oxygen gas as the temperature is raised?

• The solubility of oxygen gas decreases as the temperature is raised

• The solubility of oxygen gas increases as the temperature is raised

• The solubility of oxygen gas stays the same when the temperature is raised

10- Does a cooler lake or a warmer lake have more oxygen dissolved in its water?

• A warmer lake has more oxygen gas dissolved in its water

• A cooler lake has more oxygen dissolved in its water

• Both lakes would have the same amount of oxygen dissolved in the water

Summary:

• The solubility of a solute in the solvent at a specific temperature is the number of grams of the solute necessary to saturate 100g of the solvent at that temperature

• Gases are more soluble in cold solvent than in hot solvent

• The solubility of any gas in water decreases when the temperature increases

• The solubility of a gas is greater at lower temperature that is why we put most of the beverages in the fridge

• The fizzy taste of beverages is caused by the present of a gas, called: carbon dioxide.

Conclusion:

According to me, I preferred to give this part of the water lesson through an activity to involve students and let them discover by themselves the effects of temperature on the solubility. If I had just given them the effects without doing the activity, they will directly forget it, especially with the “decreases” and “increases” terms. I used to confuse, when I was at school, between these two terms. Therefore, I have chosen “Pepsi” as a beverage, knowing that all students will enjoy tasting my different samples. I mean who does not like Pepsi? Furthermore, when a student is confused when a gas is soluble, and at what temperature, all he has to do is to remember the experience and the “fizz” taste, and he will recognize the right answer!!