Unit 12 A Health Body

Topic

Hanging up bananas

Curriculum Link

6.2 Illustrations for the support of the claims of the particle theory: particle movement
12.2 Food substances: food test

Estimated Lesson Time

80 minutes

Introduction

Hanging up the bananas in fruit stores is a common daily life example which involves scientific concept. In this activity, students are required to think a reason for explaining this practice and design an experiment to test for the hypothesis. Students should apply the concepts of reducing sugars and food test. At the end of this activity, they need to justify the hypothesis based on the data collected.

Due to the limitations of scientific methods as well as a school laboratory, not all the hypotheses can be tested. In this case, the sweetness can be tested but the 'feeling of banana' cannot be tested. The sweetness is caused by the sugar content. Mature bananas can produces more sugar. Benedict's test can be used to quantify the sugar content in bananas. This test can work for all simple sugars except sucrose. The amount of brick-red precipitates produced in Benedict's test indicates the sugar content.

It is found that a plant hormone called ethylene can promote the maturation of fruits. Hanging up can reduce the absorption of ethylene diffusing from other fruits like apple. Thus, the maturation of bananas will be hampered and less sugar can be produced. Thus, the storage period of bananas can be extended.

Key Question

Why bananas are usually hanged up?

Learning Objectives

In this activity, the students should be able to

  1. recognise the hypothesis which can be tested scientifically;
  2. design an experiment to test the hypothesis for hanging up bananas (SP3);
  3. conduct the designed experiment (SP4);
  4. analyse and interpret data to draw a conclusion (SP5);
  5. revise own planning to test alternative hypothesis;
  6. recognise the concepts of limitations in a scientific study.

Teaching Plan

Task (Time) Brief Description Materials Objectives

Engagement
(10 min)
  • Students are engaged by the scenario to discuss and justify which reason can be tested scientifically.
 (1) & (6)

Exploration
(40 min)
  • After designing the experiment, students explore to test the reason.
  • Teachers can prepare two groups of bananas, one hanging up and one just lying on the table/floor for a few days.
 (2) & (3)

Evaluation & Explanation
(15 min)
  • Students record and interpret the data.
  • Students evaluate the data of their own group and decided if the results supporting / not supporting the hypothesis.
  • Students explain why other groups show different data.
  • Students draw a conclusion.
 (4) & (6)

Elaboration
(15 min)
  • Students elaborate another hypothesis and experimental set-up based on the present practical work if their results do not support the previous hypothesis.
 (5)

*Apparatus and materials required: