Acids and bases II

Acids and bases II

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Overview
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Marking Student Responses
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Further Resources
This task is about acids and bases.

The pH of a substance indicates whether it is acidic, basic, or neutral:

  • Acidic substances have a pH of less than 7.
  • Neutral substances have a pH of 7.
  • Basic substances have a pH greater than 7.

Using the table of pH values below, answer the following questions.

Substance pH
lemon juice 2
vinegar 3
milk 7
tap water 7
baking soda 9
milk of magnesia 11

Question 1Change answer

a)  i)  Wasps stings are basic.
         Name one substance from the table you would apply to a wasp sting to make it less painful.
     ii)  Why did you choose this substance?
 

Question 1Change answer

b)  A white substance is found on some nails in the garage. You scrape a little bit off and find its pH to be 8. 
     Name two substances from the table you could use to remove the white substance from the nails.
1. 
2. 

Question 1Change answer

c)  If the concentrations and volumes are equal, a basic substance will  an acidic substance when they are mixed together, and the new substance will have a pH of 7.
Task administration: 
This task can be completed online or with pencil and paper.
Level:
5
Curriculum info: 
Science, Investigating in science, Material World
Keywords: 
properties, acids, bases, alkalis, pH scale, neutralisation, acid-base reactions, table interpretation
Description of task: 
Students use a table of some substances and their pHs to answer four questions.
Curriculum Links: 
Science capabilities
The capabilities focus is brought about by the conversations you have and the questions you ask
 
Capability: Interpret representations
This resource provides opportunities to discuss the different ways information is represented in science e.g., pH scales, logarithmic scales.
Science capabilities: 
Interpret representations
Answers/responses: 
   Y10 (09/1997)
a) i) Lemon juice or vinegar.
ii) It will neutralise the sting, it has a low pH value.		 easy
difficult
b)
  • lemon juice
  • vinegar
 moderate
c) Neutralise difficult
Diagnostic and formative information: 
   Analysis of Correct Responses
a) i) 29% lemon juice, 71% vinegar.
Most common wrong answer, baking soda 21% of all scripts.
b) Baking soda and milk of magnesia answer in 22% of all scripts.