Download Lesson 1

Science Pull-out Programmes
Enhancing Analytical Thinking Skills through Scientific Enquiries
Lesson 1, 2 and 3 (60 min. x 3)
Level of Students: S.2 and S.3
Duration of Lessons: 3 hours
Specific Objectives:
Students should be able to
(i)
Students should be able to enhance self-analytical skills through the investigation of using the
osmotic potential of potato and beet root.
(ii)
use logic and evidence to formulate scientific explanations and models to explain how water
molecules pass through cell membranes during osmosis.
Materials and Apparatuses for each group:
(a) 1 Cork borer
(b) Fresh potatoes and beet root
(c) Beakers
(d) Salt solution A (20 g sodium chloride in 1 L water = 0.02 g/mL)
(e) Salt solution B (100 g sodium chloride in 1 L water = 0.1 g/mL)
(f) Glucose solution (100 g glucose in 1 L water = 0.1 g/mL)
(g) Salt solution Y (unknown salt concentration)
(h) Petri dishes x 4
(i) Water
(j) Stop watch or timer
Prior knowledge of students:
As students may mix up the structure cell wall and cell membrane, the teacher can ask a few simple
questions about the cell structure and cell functions to consolidate their concept.
http://en.wikipedia.org/wiki/Osmosis#Examples_of_osmosis
Suggested Learning and Teaching Activities:
Time
allocation
Remarks
5 min.
Example of osmosis:
Lesson 1 (60 min)
Teacher uses an example of osmosis to
motivate students to think about the movement
of water from and into cells.
- Roots of plants absorb water from the soil by
osmosis.
- A freshwater fish will die in high salinity water.
Reference:
http://en.wikipedia.org/wiki/Osmosis#Examples_o
f_osmosis
Teacher discusses the basic features of a plant
and animal cell with students.
10 min
Teacher briefs the students the objectives of the 45 min
investigation on the movement of water across
the plants cells (potato and beet root).
Teacher asks the students to discuss the
methods to perform the investigation and
compare the effect of osmosis in potato and
beet root.
This experiment focuses on enhancing
analytical thinking skills of students
(process skill). The terms isotonic,
hypotonic, hypertonic may be difficult for
many students, hence it is better to
introduce these terms after the
experiment. Osmosis can simply be
introduced to students as a movement of
water from and into cells.
Students are required to use a mind map to
answer the 'what', 'why' and 'how'
questions relating to the scientific enquiry
so as to work out an agreed experiment
procedure. Students are encouraged to
challenge others thoughts based on the
scientific knowledge.
Relevant questions may include:

What would happen if the potato /
beet root is immersed in water, salt
solution or sugar solution? Students
are required to predict the results.







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How should the experiment be
started?
What treatment should be done to the
potato strips?
How to cut identical potato strips?
How to measure the strips?
What variable should be kept
constant?
How the time should be measured?
What data should be taken?

What should be the result table
looked like?
How is the control set-up?


One potato strip or more?
Division of labour?
Students are invited to present their mind
maps and work flow. Other students may
criticise and make suggestions. The
teacher concludes the experimental design
after the presentations.
Lesson 2 (60 min)
1 hour
Students’ presentations should include
observation, result (How to plot the
graph? Scaling? Extrapolation?), data
interpretation, conclusion, source of error,
and recommendation to modify the
experiments.
Students are required to present their data and
results.
45 min.
(10 min.
for each
group)
All agree? Questions and further
suggestion? Pool class data? Use of excel?
Experimental technique?
Teacher comments on students’ presentation
and concludes the activity on osmosis.
15 min.
Through this activity, students should
focus more on the process skills needed in
Students are required to perform the
experiments in groups - record the result,
analyze the data collected and discuss among
themselves the conclusion, possible source of
error and suggestion to improve the
experimental design.
Students are required to find out the
concentration of the unknown solution.
Lesson 3 (60 min)
the experimental design, data analysis and
interpretation, and drawing conclusion
based on the evidence.
Extension for very highly able students
Assignme
nt or
activity
(1-2
hours)
More able students are encouraged to
study the concepts of the terms Isotonic,
hypertonic and hypotonic through
researching in the library and on the
Internet. They are also required to write a
summary about these terms.