Lesson 20

Lesson 20: Microorganisms Can Spoil Food

Learning Objective

Understanding food spoilage

Syllabus Correlations

· Theme: Investigating Materials

· Learning Area: Food Preservation

· Learning Objective: Understanding food spoilage

Learning Outcomes:

Pupils should be able to:

· state that microorganisms can spoil food;

· state the conditions for microorganisms to grow.

Concept(s) Introduced:

· microorganisms can spoil food;

· conditions for microorganisms to grow.

Skills Covered:

· Observing, classifying, making inferences, interpreting data, making conclusions, comparing and contrasting.

Vocabulary/ New Words:

· food spoils, microorganisms, food poisoning, vinegar, pH paper, decayed, food spoilage

Value(s) Incorporated:

· Having an interest in and curiosity about the environment.

· Being diligent and persevering.

· Realising that science is a means to understand nature.

· Thinking rationally

· Analysing the things around us

Materials Needed:

-

Point(s) to Note:

Explain what are microorganisms and the conditions for them to grow.

Teaching Strategies
Set Induction	Show picture of three examples of food with fresh and spoilt conditions. Tell pupils what cause the food to spoil. Emphasise that microorganisms cause food to spoil. Encourage pupils to suggest some other possible causes of food spoilage. Discuss it in the class Component: Introduction
Step 1	Play the content component. Pupils watch the videos of microorganisms. Teacher explains to pupils that microorganisms require a specific condition to live. Ask pupils what is the effect of microorganisms to food. Teacher explains that microorganisms cause damages to food by releasing chemical substances that act on the food. Emphasise that these chemical substances are harmful to human body. Ask pupils whether any of them had food poisoning before. Play the content component. Ask pupils the five conditions for microorganisms to grow. Play the content component. Teacher highlights on microorganisms’ need for air. Explain that microorganisms grow in damp air in dark place. Ask pupils whether microorganisms can grow without air. Play the content component. Teacher highlights on microorganisms’ need for water. Explain that microorganisms are active in moist conditions. Ask pupils whether microorganisms can grow without water. Play the content component. Teacher highlights on microorganisms’ need for nutrients. Ask pupils what food has the nutrients required by microorganisms. Show the video on the process where milk becomes spolit. Explain that milk has the required nutrients. Ask pupils whether microorganisms can grow without nutrients. Play the content component. Teacher highlights on microorganisms’ need for suitable temperature. Ask pupils what is the required temperature. Explain that the optimum temperature is room temperature. Ask pupils whether microorganisms can grow at other variable temperatures. Play the content component. Teacher highlights on microorganisms’ need for suitable level of acidity. Ask pupils what is the required level of acidity. Explain that microorganisms cannot grow in a very acidic medium. Ask pupils what solutions are acidic. Play the content component. Teacher makes a summary of the different types of conditions for mircoorganisms to grow. Component: Content
Step 2	Play the activity component. Help pupils to identify conditions for microorganisms to live. Pupils need to fill in the blank of an incomplete sentence to complete this activity. Click check to verify their answer. Pupils can discuss with their friends to do this activity. Component: Activity
Step 3	There are five questions in this component covering the learning outcomes. Questions 1 to 3 are objective questions. Q4 is a drag and drop activity. Pupils drag and drop the correct answers for the questions. Q5 consists of true or false questions. Pupils need to identify whether the statements are true or false. Use evaluation sheets to assess the pupils’ understanding of this lesson. Component: Evaluation
Step 4	Explore the method to measure acidity and alkalinity of a solution. Teacher introduces to pupils the use of litmus paper and pH paper. Teacher explains to pupils the pH scale. pH 1 indicates that the solution is acidic. pH 14 indicates that the solution is alkaline. pH 7 indicates that the solution is neutral. Emphasise that microorganisms grow well under neutral condition. Suggest to pupils to carry out a finding on different types of solutions and present their finding in the class. Component: Extension
Conclusion	Conclude the lesson by playing this component to further reinforce understanding of the lesson. Help pupils to identify what causes food spoilage. Highlight the five conditions that enable the microorganisms to grow. Component: Summary