Lemon juice reactions

Lemon juice reactions

Pencil and paperOnline interactive
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Further Resources
This task is about changes to substances when you add lemon juice to them.
 
A physical change is reversible - it is a temporary change. A chemical change cannot be reversed - it is permanent.
 
Rahera was doing some science in the kitchen. She squeezed the juice from two lemons and divided it equally into two glasses.
She put a teaspoon of baking soda (sodium hydrogen carbonate) into one glass.
She put a teaspoon of salt (sodium chloride) into the other glass.

Question

In the glass with baking soda there was lots of fizzing – in fact the foam spilled over the rim of the glass!
What type of change occurred?
 

    • Physical change

    • Chemical change

Explain your decision.

Question

In the glass with salt, the salt seemed to disappear. 
What type of change occurred?

    • Physical change

    • Chemical change

Explain your decision.
Task administration: 
This task can be completed with pencil and paper or online with some auto-marking.
Level:
5
Curriculum info: 
Science, Investigating in science, Material World
Keywords: 
physical changes, chemical change, temporary changes, permanent changes
Description of task: 
A description of two 'reactions' with household chemicals is outlined. For each students identify if the reaction is chemical or physical and provide an explanation for their answer.
Curriculum Links: 
Science capabilities
The capabilities focus is brought about by the conversations you have and the questions you ask.
 
Capability: Use evidence
This resource provides opportunities to discuss criteria used to provide evidence and how the criteria is interpreted in the examples given.
Answers/responses: 
  

Y9 (08/1997)

Y10 (08/1997)
a) i)
ii)		 Chemical change.
Reaction takes place. Fizzing indicates that a gas has been released.		 difficult moderate
b) i)
ii)		 Physical change.
No reaction takes place. The salt particles still exist but are now mixed/dissolved with the lemon juice.		 difficult moderate