Reading and writing task in Chemistry –

Tests find concentration of active ingredient may be too low in some household bleaches (15 July 2009)

Objective:

Through watching TV news and reading news articles of chemistry-related issues, students are guided to relate their chemistry knowledge with daily-life and social affairs. In this activity, students are required to analyse a STSE (science-technology-society-environment) issue using scientific and logical thinking. Moreover, the activity aims to use daily-life related current affairs to activate students’ interest and consequently encourage students to learn chemistry via reading and writing.

Curriculum link:

NSS Chemistry

Topic VII Redox Reactions, Chemical Cells and Electrolysis

Topic XIII Industrial Chemistry

CE Chemistry

Section 5 Chemistry Cells and Electrolysis

Section 6 Products from Important Process

Tasks:

Activity 1 – Watching TV news

Students watch a news clip about the tests on the concentration of active ingredient in household bleaches (15 July 2009):

http://mytv.tvb.com/news/newsroundup/7776/613

While watching the news, students should write down in the worksheet three queries about the news. The queries should be science or chemistry related, such as “why is household bleach unstable?”

Activity 2 – Reading activity

1. Students read the article from the Consumer Council released on 15 July 2009:

“Consumers advised to pay attention to household bleach concentration for proper dilution for use as disinfectant – CHOICE #393” (http://www.consumer.org.hk/website/ws_en/news/press_releases/p39301.html)

2.  From the article, students try to find the answers for their three queries.

3.  Teacher discusses the queries and the answers with the students in the class.

4.  If answers are not found from the article, students search for answers for their queries on the internet or in reference books.

Activity 3 – Writing activity

The student is assigned the role of a reporter for the school newspaper. The student is required to write an article for the coming issue of around 300 words based on the test results on household bleach from the Consumer Council. The article should include the following:

(a)  The chemical properties of sodium hypochlorite in relation to its bleaching and disinfecting action

(b)  Give advice on the purchase and safe use of household bleach. Relevant explanation with chemical equations (if appropriate) should be provided.

References:

http://en.wikipedia.org/wiki/Sodium_hypochlorite

http://en.wikipedia.org/wiki/Hypochlorite

Cotton, F.A; G. Wilkinson (1999). Advanced Inorganic Chemistry (Sixth Edition). John Wiley and Sons Inc. (ISBN 0-471-17560-9)

http://www.astm.org/Standards/D2022.htm - ASTM D2022-89(2008) Standard Test Methods of Sampling and Chemical Analysis of Chlorine-Containing Bleaches.


Worksheet

Reading and writing task in Chemistry –

Tests find concentration of active ingredient may be too low in some household bleaches (15 July 2009)

Activity 1

Write down three queries while watching the TV news

1.
2.
3.

Activity 2

From the reading article, answer the queries you have written down.

Answer 1
Answer 2
Answer 3