Year 10 Science · Unit 2 · Lesson 19
Challenge Worksheet
Learning Goals
Evaluate the claim
Someone claims...
"Mixing bleach and vinegar makes a more powerful cleaner. Bleach kills germs and vinegar cuts grease, combine them and you get both benefits at once. I've been doing this for years and my house has never been cleaner. The chemical reaction between them makes an even stronger disinfectant. Natural vinegar balances the harshness of bleach, making it safer on surfaces."
(a) What chemistry actually occurs when bleach (NaOCl) is mixed with vinegar (acetic acid, CH₃COOH)? Name the products formed and identify whether any are hazardous. Include the reaction type.
(b) Identify two specific scientific errors or misleading statements in the claim above. For each error, explain the correct science.
(c) The person says "I've been doing this for years and my house has never been cleaner." Explain why this personal experience (anecdote) is not reliable evidence that the mixture is safe or effective. What type of evidence would a chemist or toxicologist require?
1. "Paracetamol is synthetic and therefore more dangerous than natural herbal remedies." Evaluate this claim using at least one specific example and the principle that "dose determines toxicity."
2. A science blog post is funded by a chemical company and claims their new fertiliser has no environmental impact. Describe two features of this source that should make you question its reliability, and explain how you would find more trustworthy information.
Wrap Up
In one sentence, explain why a dangerous household chemistry claim needs to be rebutted using chemistry knowledge rather than just saying "I read it online that it's dangerous."