Teachers TryScience

Blame it on the pH!

May 24 2016

Source: LLF India

Summary Information

Topic:

Chemistry

Workplace Skills:

Investigation Design

Discussion

Teamwork

Target Grade (Ages):

Grade 10 (Ages 15-16)

Diversity Indicators:

Grade 10- Students

Tab Wrapper

LESSON

Goals and Prerequisites

Goals:

To understand the importance of pH in our lives.
To learn the method of making own indicator using red cabbage and test its accuracy when evaluated against a readymade indicator.
To get introduced to the concept of hydroponics agricultureand understand the importance of pH while growing plants.

Prerequisites:

Knowledge of basic properties of acids and bases.
Knowledge of the pH scale and checking the pH of a liquid using a litmus paper or litmus indicator.
Ability to differentiate between acids and bases. e.g. by taste.
Knowledge of basic requirements to grow plants.

Instructional Objective(s)

At the end of the lesson, students should be able to:

Differentiate between acids, bases and neutral things around us.
Understand the importance of pH value in their lives.
Learn the importance of pH value for the growth of plants.
Understand the role of environment and habits and how these are critical to maintaining the pH value balance on the earth.
Understand how, with the knowledge of, basic concept of acids and bases, engineers are able to create a lot of things that contribute to the health, happiness and safety of society.

Instructional Resources

Background:

Instructional Resources

Introduction –

Ascertain students’ prior knowledge about the acid and bases we see around us and encounter daily in our lives.Kindle their minds by encouraging a large group discussion about the need for these acids and bases for the survival on this earth. Put forward some questions like:

What would be the consequences if acids were wiped out from this planet?
Do you think our advance technology allows us to be the whole and soul manipulators of acids and bases on this earth? Discuss.
How do you think acids and bases effect what we eat?
How is measuring pH important to engineers?

Conclude the discussion by showing them the video with link

https://www.youtube.com/watch?v=A8bKPPOB0Rs

which will explain the importance ofpH around us, giving an overview of the topic and

https://www.youtube.com/watch?v=LS67vS10O5Y

will also introduce the detailed ionic concepts of pH.

Divide the class in groups of 6 and give each group a K-W-H-L chart. Have each group fill ‘K’ , ‘W’ and ‘H’ columns about acids, bases and pH and how important is pH in our lives. Check and discuss K-W-H-L charts with each group.

Inform the students that they are going to developpH indicator strips using red cabbage,taking advantage of its natural ability to perform as a pH indicator and evaluate their accuracy, by testing the pH of the liquids using an engineer-designed tool, pH indicator strips.Using red cabbage indicator the students further study the affect f acid rain on plants. Ask the students to give their engineering teams interesting names.

Pass the set of material to each group.
Instruct the students that they have to make the pH indicator strips using the red cabbage, then test the accuracy against the given readymade pH strips. The students plant the given stems in three beakers in which the water will be acidic, neutral and basic and study the growth to draw conclusions.
Students will spend time in investigating, planning, creating, manipulating and evaluating during the entire activity.

Integration of the concept with other STEM Subjects:

Topic as integrated with Science (Biology)- Monitoring the growth of plants and the effect of pH value on the growth.Students also learn the basics of hydroponics. Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral solution only, or in an inert medium, such as perlite or gravel.

Topic as integrated with ELA (English language art)- Improving vocabulary by learning new terms and meanings, making inferences, writing a report and summarizing.

Topic as integrated with Math- Statistics and data analysis to monitor the growth of plants and numerical comparison of pH values observed from two different indicators.

Materials:

Material Needed

For each student:

Hand Gloves
Safety Goggles
Aprons
Engineering Design Process Workbook
Handout for students
KWHL Chart: http://coolaustralia.org/wp-content/uploads/2013/03/KWHL1.jpg

For each group:

1 red cabbage
large pot, water, stove/Bunsen burner, strainer
bowl to hold red cabbage indicator from pot
Rimmed rack
03 clear glasses or clear glass bottles
Marker to label bottles
filter paper (coffee filter paper works well) – cut the coffee filter paper into rectangle (it is usually available round)
2tablespoon/ 2 ink droppers
Baking soda(mix 1 teaspoon with 1 tablespoon of water)
Vinegar
6 pH indicator strips
pH colour chart (chart given in the handbook)
Paper
Pencil
03 Cuttings of money plant /mint leaves/ tomato plant
Chart paper (for poster)
Internet facility for research work

For the entire class:

To create a mini field with optimum yield!

Camera
Liquid pH indicator orpH strips (to test the accuracy of the prepared red cabbage indicator strips)
Measuring tape
3 packs of sketch pens/ crayons

Handout for students

Procedure:

Engineering Designing/STEM Based Project

Introduction

To start, you may want towatch the - What is Environmental Engineering video below

https://www.youtube.com/watch?v=ZdYnTbgwVis

and then initiate a discussion regarding as to how pH is an important aspect of engineering. Environmental and chemical engineers examine pollutant substances to find out whether they are acid or base to know what kind of reactions they cause. Electrical engineers design batteries. Chemical engineers design everything from pharmaceuticals to soap to glue to bubble gum using pH value. Civil engineers design water and waste treatment plants maintaining pH levels for towns and factories.

Encourage the students to follow the engineering design process in their following activity too. Explain the process if they are unaware of the process or if time permits you can show them the video https://www.youtube.com/watch?v=fxJWin195kU.

Part – 1 –Planning and developing the indicator

Discuss with students about environmental and chemical engineers who have an important and challenging task to develop their own natural pH indicators and use them to study the growth of plants in different pH levels of water and thereby stating the dangerous effects of acid/bases on plants and further enlist the causes of the danger and the steps we can take to overcome them. Conclude with the video https://www.youtube.com/watch?v=Nf8cuvl62Vc which explains about acid rain.

Encourage students to sit in selected teams and brain storm. Students first need to understand the problem at hand and then work towards it by planning their activity.

While planning, students need to follow some norms:

Equal distribution of work within teams is a must for timely completion.
Teams need to prepare their own pH indicator and evaluate its accuracy using the readymade indicator given to them.
All observations need to be noted in the workbooks made available to them.
Three bottles/ jars need to be labelled A-acidic, B-neutral, C-basic with their respective pH levels.
Students need to adjust the amount of vinegar and baking soda in the three bottles of water to get the required pH levels.The task is to study the effect of acidic water on plants to understand the importance of correct pH for good growth of plants and how pollution is disturbing the pH the soil.
Teams are required to monitor and record growth of plants for 2 weeks(use Engineering Design Workbook) and present their findings with their conclusions and suggestions either as a report, or a poster or a Power Point presentation or a combination of these.
A plant takes time to grow. Whileplanning students should set up an observation schedule and pH maintenance rotation to participate in. Each student in a team will serve as a ‘plant caretaker’ to ensure their plants are getting sunlight, water with pH levels as set and make observations to make sure they are able to grow within the two week time frame.
The method to prepare the red cabbage indicator is given in the handbook.

Reassemble the class as a whole group and take them through the presentation using link http://theplantdoctor.pbworks.com/f/Introduction+to+Hydroponics.ppt that introduces them to hydroponics(growing plants in water). Also take the opportunity to discuss the advantages of hydroponics keeping the pH level in mind. (Teachers can skip or hide slides which are out of the scope of students learning or requirement.)

Part – 2 –Evaluating Accuracy of Prepared pH Indicator

Students to make an acidic solution in a beaker by adding vinegar drops to it.
Students insert the red cabbage indicator strip in the solution. Once the colour changes, they note the pH of the solution using the given pH colour chart (Handbook)
Students measure the pH of the solutions using red cabbage indicator and also by using readymade litmus indicator (litmus pH indicator given by teacher). They compare both readings to evaluate accuracy of the prepared red cabbage indicator. If the variance ishuge,teamsshould introspect to understand what went wrong and perhaps redo the experiment.

Part – 3 –Test and Re-engineer for Required pH Levels in Planters

Students fill three beakers/flasks/ glasses (any transparent containers with a little narrow mouth).
Label the containers – A, B, C(use markers or stickers)
Students test and re-engineer the process of adjusting the amount of vinegar and baking powder. The attempt should be to adjust the pH value of containers – Container A to below 5, Container B to 7 and Container C to above 9 respectively.

Part – 4 –Planting and Observing Growth

Teams are required to plant given (teacher brings same plant stems for all teams) stems in the three labelled planters and keep them either in the chemistry lab or classroom.In the forthcoming two weeks, after introduction of the conceptand conduct of the experiment -

Students need to record growth of the plants and pH value of the different medium used in the table given in their respective Engineering workbooks.
Students need to maintain the pH value of the three planters to the ones set at the beginning of the activity.

Part – 5 –Inferences,Summarization and Presentation

After two weeks students should be given time to reassemble in their respective groups to share their learning, draw inferences from the tabulated readings, do research work on the causes and effect of too acidic/too basic water and soil.
They list and record environmental conditions which cause the damage.
They also list prevention methods and the difference each one of us can make to avoid the harm being caused to not only mankind but to all life on earth.
The teams need to make their posters illustrative, with appropriate slogans and present them in an effective manner.
Culminate the activity by asking students to reflect on the entire design process. Have students fill in the L column of the K-W-H-L.
A question answer round, led by teachers should be conducted.
To conclude ask the students to answer summative questions in the workbook.

Rubric

Rubric Presentation

Extensions

Students cancreate water garden (Aquaponics Lab) to produce leafy plants from water and without soil. They can note the importance of pH for the fish and the plants.
Students can collect water from their homes, school, tanks, canals and rivers in their vicinity or city and test the pH value of each sample collected. They can list the dangers of consuming and using acidic i/basic and polluted water. (including ground water). They can suggest projects of making the water safe for the cities consumption.
Students can collect tablets of certain broad spectrum antibiotics and check the pH value of their solutions (only under supervision!). They can make inferences and list the effect they have on our body’s pH level, thus, understanding why the doctor prescribes an antacid along with an antibiotic!

Assessments and Rubrics

Pre-activity – Discussion questions

Review with students what they know about pHcolour chart? How was it possible to know the pH value of a substance without the chart during earlier times?
Why do you think chemicals in inside our body are both useful and harmful for us?
Do the chemicals have the same effect on the plants too? Explain.
How are we responsible for increase in the chemical content and acidification of the water and soil on earth?

Activity Embedded – (Formative Assessment)

Evaluate the student on her knowledge of the topic and contribution to team, while building the model and documentary using the suggested rubric. Many such rubrics are also available on the net.
Evaluate the student workbook book to gauge the student’s thinking, creativity and learning while on the project.

Post activity –

Show and tell – Evaluate the teams on their posters and presentations using the given rubric.

Engineering Design Workbook

Rubric

Rubric Presentation

Credits

Credits