Students will measure the acidity of different local fruits by using an iodine/starch solution as an indicator. They will prepare the indicator solution, weigh and grind the fruit samples, add the fruit solution to the indicator and count the number of drops needed to change the color. This will be repeated for 3 test tubes per group. The results will be presented, compared between groups and discussed. The goal is for students to understand the properties of acids and bases through an inquiry-based experiment.

1. Name of School: Nongbaudeang Wittaya School___Week: ___17________
Year level: ___M.2_______Subject: ___Science 3__Prepared by: _Sriwai Kanhathaisong
Overview & Purpose
As a final experience for the learning of acids and bases,
students are invited to pick up some local fruits and take to
school. There they will measure the level of acidity by using an
iodine/starch solution as indicator, hence they will compare their
results with those of other groups
Education Standards Addressed
Standard SC3.1: Understanding of the properties of substances; the
relationship between the properties of substances and the structures and
binding forces between particles; having investigative process for seeking
knowledge and scientific reasoning; transferring and putting the
knowledge into practice
3. Experiment and explain the principles of substance separation
by methods of filtering, crystallization, expunctions, distillation and
chromatography, and put the knowledge into practice.
Standard SC3.2: Understanding of the principles and the nature of change
in the state of substances; the solution formation; the chemical reaction;
having investigative process for seeking knowledge and scientific
reasoning; transferring and putting the knowledge into practice
3. Search for data and discuss about the effects of chemical
substances and chemical reactions on living things and the environment.
Teacher Guide
Learning Objectives
Students shall be able to:
- prepare the indicator (iodine/starch
solution)
- measure the level of acidity of fruit
samples
- compare their results with other
groups
- discuss the experience by analyzing
the procedure and the achieved results.
Methodology
This lesson has been developed by using the enquiry
based learning strategy and the 5-e model has been
instantiated.
At first students’ interest, the Engaging stage, was
raised by informing them about the medical properties
of vitamin C. Then it was asked where it would be
possible to find that medication, to heal their flu, in
local fruit, and which one was the best since
containing the largest amount of medicament.
Students were then asked to Explore the topic by the
experience here after described. That saw them very
keen into its performing because correlated to their
interests. The Explanatory stage was conducted
during the presentation of the results of the
experience: the teacher’s role was to elicit the
explanation of their understanding by asking wh-kind
open questions, and when required, by fixing their
mistakes by asking additional questions that would
cause a re-thinking of their account.
Finally the Evaluation was made by discussing their
final report with the whole class and students had the
chance to choose the paper they considered more
expressive of the obtained results.
As Extension they could perform some experiences at
home, on the base of their ideas, and by other means
easier to find in household products.
Materials needed by 1 group
- Fruit samples
- 3 Beaker 100 ml
- 3 Test tubes , largest size, with rack
- 1 Mortar
- 1 graduated cylinder 10ml
- 1 spatula
- 1 dropper
- 1 glass rod
- 1 funnel
- 1 filter paper
- 1 bottle of de-ionized water
- 1 complete alcohol burner set
- 1 Triple beans scale

2. Assessment
-Observation of students during the
experiment
- Evaluation of the ability to understand
the results
- Evaluation of the communication skills
- Evaluation of the ability to ask
questions
- Report paper
Presentation 10 min
The teacher will say how to perform the experience:
1) Students will be asked to prepare the indicator by mixing 2 spatulas of starch in 200 ml of
about 10 min until it will become transparent and jelly.
2) 100 g of fruit sample will be weighted and grinded in the mortar. When completely smashed
added. The product will be stirred and filtered.
3) In one test tubes will be poured 1 ml of the starch jell prepared at point 1, 9 ml of water and 1 drop of 1% iodine solution. The all will
be shaken.
4) Drops of the fruit solution prepared at point 2 will be added to t
drops required to turn the indicator color from blue to transparent.
5) The experience will be repeated for the 3 test tubes. Students are expected to count and average the number of drops required
the indicator color.
Activitiy 30 min
Students will perform the experience as it was presented, while the teacher will supervise and evaluate their job.
Conclusion 10 min
Students will present the results collected during the experience and they
be initiated by the teacher with questions such as:
“What is the most acid fruit? (that one that requires more or less drops)
“How many drops do you need on average?”
“When did you notice a variation?”
Finally, as H.W., they will write a report of experiment.
Summary
-Some interesting question were asked by
students:
“What indicator can we use, if we would
like to do at home?”
“Is vitamin C present only in fruits?”
“Does chilly contain Vitamin C?”
“What else can we test with this
indicator?”
The teacher answered to some of these
questions,
Other resources
- Handouts explaining
will be distributed
to the number of elements forming the compound.
The teacher will say how to perform the experience:
Students will be asked to prepare the indicator by mixing 2 spatulas of starch in 200 ml of water. Then the mixture will be warm for
about 10 min until it will become transparent and jelly.
of fruit sample will be weighted and grinded in the mortar. When completely smashed, to form a
stirred and filtered.
1 ml of the starch jell prepared at point 1, 9 ml of water and 1 drop of 1% iodine solution. The all will
of the fruit solution prepared at point 2 will be added to the indicator prepared at point 3. Students must count the number of
drops required to turn the indicator color from blue to transparent.
The experience will be repeated for the 3 test tubes. Students are expected to count and average the number of drops required
Students will perform the experience as it was presented, while the teacher will supervise and evaluate their job.
Students will present the results collected during the experience and they will compare their data with those of other groups.
hat requires more or less drops)”
a report of experiment.
Additional notes
-Would be great
some groups cannot conclude the experience
Other resources
explaining the vitamin C (l-ascorbic acid)
will be distributed. Particular evidence will be given
to the number of elements forming the compound.
water. Then the mixture will be warm for
to form a pulp, 100 ml of water will be
1 ml of the starch jell prepared at point 1, 9 ml of water and 1 drop of 1% iodine solution. The all will
red at point 3. Students must count the number of
The experience will be repeated for the 3 test tubes. Students are expected to count and average the number of drops required turning
Students will perform the experience as it was presented, while the teacher will supervise and evaluate their job.
will compare their data with those of other groups. A discussion will
Additional notes
Would be great having more than one period, in fact
some groups cannot conclude the experience.