Acid, alkali or neutral

Acid, alkali or neutral

Pencil and paper
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Further Resources
This task is about identifying the effect of indicators on acid, alkali and neutral substances.
Part A: News from hues
1. Put a drop of red cabbage indicator solution in each spot in the top row of a spotting tile.
2. Cut the red litmus paper into four pieces, place a piece in each spot of the middle row of the spotting tile.
3. Cut the blue litmus paper into four pieces, place a piece in each spot of the bottom row of the spotting tile.
 
 
spotting-tile-labels.png
 
4. Add one drop of white vinegar to each spot in column 1.
5. Add one drop of baking soda solution to each spot in column 2.
6. Add one drop of water to each spot in column 3.
7. Add nothing to each spot in column 4.
8. Write your results in the circles above.
   
Results
a)
Use coloured pencils to colour in the spots on the table above to show the colour changes that have occurred.
NOTE: white vinegar is an example of a weak acid, baking soda solution is a weak alkali, and water is a neutral solution.
 
b)
Complete these sentences
 
Acids make indicators go ______________________.
 
Alkalis make indicators go _______________________.
 

Neutral solutions have _______________________ on the colour of a substance.

 
c)
Why did one column of the spotting tile have nothing added to it?  
 
 
 
 
 
 
 
  Part B: Acid, alkali or neutral 

  • Test each of the substances you have been given and find out if they are acid, alkali, or neutral.
  • Use a similar method to part A. Put a drop of each substance in a spotting tile and then add a drop of red cabbage indicator.
a)
Complete this table to show your results. 
 
Substance tested Colour change? Acid, alkali, or neutral?
Lemon juice
 
 
  
Bleach
 
 
  
Orange drink
 
 
  
Washing powder
 
 
  
Water
 
 
  
Cleaner
 
 
  
 
b)
 
Rank the substances you tested from the strongest acid to the strongest alkali.
 
 
 
 
 
 
 
 
Task administration: 

This task can be completed with pencil and paper and other equipment.

This task has 2 parts. Part B follows on from part A, but can be done at a later stage. Pre teaching of acids, alkalis and neutral solutions is required.

Part A - News from hues

Equipment:

Scissors; spotting tiles; eye-droppers; red and blue litmus paper; coloured pencils (these need to include the colours red, blue, purple, green, and yellow); red cabbage; kitchen blender or similar; hot and cold water; sieve; air-tight jar; white vinegar, baking soda.

Preparation of red cabbage indicator solution:

  1. Cut up a 1/4 of red cabbage and place it in a kitchen blender.
  2. Add 1 cup of hot water.
  3. Blend until a fine mush.
  4. Sieve.
  5. If necessary store in an airtight jar overnight in the fridge.

Part B - Acid, alkali, or neutral

Equipment:

Eye-droppers; spotting tiles; red cabbage solution; a range of household acids and alkalis, e.g., lemon juice, bleach, colour free orange drink sachet, washing powder, water; Mr Muscle – multi purpose foam cleaner.

  • The students may need reminding as to the effect of the red cabbage indicator on acids and alkalis.
  • All substances to be tested need to be in a liquid form.
  • You may want to spray the cleaner in a small container for use by students.
Level:
5
Curriculum info: 
Science, Investigating in science, Material World
Key Competencies: 
Thinking
Keywords: 
properties, acids, alkalis, investigation, indicators, classification, practical
Description of task: 
This practical task has two parts. The first part of this practical requires students to observe the effects of different indicators on different substances. Students use these results to identify if some other substances are acid, alkali, or neutral.
Curriculum Links: 
Science capabilities
The capabilities focus is brought about by the conversations you have and the questions you ask.
Capability: Gather and interpret data
This resource provides opportunities to discuss looking for patterns in oservational data to guide inferences.
Science capability: Gather and interpret data (TKI)
 
Answers/responses: 
PART A
a)

b)

Acids make indicators go red and alkalis make indicators go blue. 
Neutral solutions had no effect on the colour of the indicators.
c) So it can be used as a comparison.
 

 

PART B
a) All colours correctly described (see chart below).
Colours should be described clearly enough to distinguish between differend acids, e.g., shades of red should be used for acids (see chart below).
a)  

Substance tested Colour change Acid, alkali, or neutral
Lemon juice pink Acid
Orange drink light pink Acid
Washing powder blue/green Alkali
Water N/C purple Neutral
Cleaner green Alkali
b) Lemon juice orange drink water washing powder cleaner.