Find the best solvent

Find the best solvent

Pencil and paper
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Further Resources
This task is about carrying out a practical task to find out which of two liquids are solvents for any three given solids.

How to do this task:

  • Plan and carry out a "fair test" to find out which liquid is the best solvent. (A solvent is able to dissolve another substance, usually a solid).
  • Complete the results table and write a conclusion.
  • Liquids to use: water and cooking oil.
  • Solids to use: salt, sugar, and cocoa.
  • You might like to think about:

What does "best" mean?
What are you going to measure?
What will you need to keep the same?
Will it be a "fair test"?

a) Describe how you are going to carry out your fair test.
 
_______________________________________________________________________
 
_______________________________________________________________________
 
_______________________________________________________________________
 
_______________________________________________________________________
 
_______________________________________________________________________
 
_______________________________________________________________________
 
_______________________________________________________________________

b)
Write your results in the table below.
 
Liquids Solids
Salt Sugar Cocoa
Water      
Cooking oil      
   
c) What was your conclusion?
 
_______________________________________________________________________
 
_______________________________________________________________________
Task administration: 

Equipment:

Water; cooking oil; cocoa; salt; sugar; measuring cup; teaspoon; 6 small containers with lids (e.g., a container which will hold 100 mL when full).

  • This task can be done in groups of three.
  • You may need to assist students by specifying the amount of liquid and solid to be used, and by instructing them to shake each mixture to encourage the solid to dissolve. Approximately 1/4 of a teaspoon of solid, with each container 3/4 full of liquid will give you a result.
  • As an alternative to requiring students to write a conclusion you could ask:

       i) Which was the best solvent?
       ii) Why was it the best solvent?

Level:
4
Curriculum info: 
Science, Investigating in science, Material World
Keywords: 
properties, solvents, fair testing
Description of task: 
Students are given some solids and liquids for this practical task. They plan how they would find out which liquids are solvents for any given solid, carry out the task, and write a conclusion.
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 the importance of controlling variables when using fair testing for an investigation.
Science capabilities: 
Gather and interpret data
Making Better Sense: 
Dissolving
Answers/responses: 
a)
Plan should include:
  • Uses the same general method for each trial, e.g., mixes each solid with each liquid in turn and shakes the jar.
  • Uses the same amount of liquid for each trial.
  • Uses the same amount of solid for each trial.
  • Uses the same method to check if the solid has dissolved, e.g., observing solids left at the bottom of the jar/pouring out the liquid to see if any solid remained.
b) All 6 cells in table filled out with accurate description of whether the solid dissolved or not.
c) Conclusion reflects results, e.g., water is the best solvent.