Unit 7 Living Things and Air

Topic

What are the products of photosynthesis?

Curriculum Link

7.1 What is air made up of: test for oxygen, carbon dioxide and water
7.4 How do green plants obtain energy: starch and oxygen are products of photosynthesis

Estimated Lesson Time

80 minutes

Introduction

In this activity, students will deduce the products of photosynthesis based on different hands-on practical. At the end of lessons, they are expected to state the two products of photosynthesis, starch and oxygen, when the plant is placed under light. In addition, they should describe the energy conversion involved and its significance to plants. Moreover, they should be aware that not only leaves but also other parts of the plant contain starch even they cannot carry out photosynthesis.

Key Question

What can plant produce in the presence of light?

Learning Objectives

In this activity, the students should be able to

  1. conduct gas test and iodine test (SP 4);
  2. deduce that plant can produce oxygen and starch in the presence of light (SP 5);
  3. modify the existing set-up for a new experimental objective;
  4. describe the conversion of energy in sunlight to chemical energy in green plants and its significance;
  5. recognise that not only leaves but also other parts of the plant contain starch even they cannot make starch.

Teaching Plan

Task (Time) Brief Description Materials Objectives

Exploration
(15 min)
  • Students explore the tests for different gas released from the water plant.
  • Teacher should prepare the set-up before the lessons. What the students do is just to test any gaseous product. If the relevant apparatus are not sufficient, teacher can demonstrate the tests.
 (1) & (2)

Elaboration
(10 min)
  • Students elaborate how the set-up can be modified in order to study the effect of light intensity on the rate of products released.
  • Students analyse the data given to draw the conclusion.
 (3)

Exploration & Explanation
(40 min)
  • Students explore if two types of leaves (illuminated and non-illuminated), two soil samples and different solutions can turn iodine solution to blue-black. Hence, students deduce that only starch can turn iodine solution to blue-black and the starch can be only found in plant under the presence of light. The iodine test on leaves can be commonly found in local textbooks.
  • Students explain the significance of the energy conversion of food making process in plants.
 (1), (2) & (4)

*Apparatus and materials required: