Exploring Our Fluid Earth

Teaching Science as Inquiry

 

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Activity: Solubility
Table of Contents
Activity: Solubility
Materials
  • Distilled water
  • Ethyl alcohol
  • Vegetable oil
  • Sodium chloride (table salt)
  • Sugar
  • Starch
  • Baking soda
  • 10 mL graduated cylinder
  • Stopper to fit graduated cylinder
  • Containers and lids to store solutions
  • Labeling tape
  • Waterproof marking pen
Table 3-3. Chemical structure, polarity, and bonding of selected liquids.

Liquid

Bonding

Polarity

Model Molecule

Distilled water*

Covalent

Highly polar

 

Alcohol

Covalent

Slightly polar

 

Oil **

Covalent

Nonpolar

 
* Distilled water is water that has had dissolved ions removed. It is pure H2O. 
**Oils are usually mixtures of different kinds of molecules
 
Procedure
  1. Use the information on the liquids in Table 3.3 and solids in Table 3.4 to predict how much of each solid solute the solvent will dissolve.
    1. Record the properties of each solvent and solute in Table 3.5. 
    2. Using the terms all, some, and none, record your predictions about how much of each solute will dissolve in each liquid in Table 3.5.
  2. Determine how much solid solute each solvent can dissolve.
    1. Obtain the solvents and solutes you are assigned to work with.
    2. Test the solubility of the solutes in the solvent. Put 2 mL of your first solute into a 10 mL graduated cylinder, then fill the graduated cylinder to the 10 mL line with your solvent liquid. 
    3. Stopper the cylinder, shake the contents gently for 10 seconds, and let the mixture stand until settling stops, approximately 20 seconds. Shaking vigorously may temporarily form a suspension.
    4. Determine how much of the solid dissolved. Record your observations as all, some, or none in Table 3.4.
    5. Optional: Save your solution to test conductivity. Store in containers with airtight lids to prevent evaporation. Label the containers with your name and the solution.
    6. Wash the graduated cylinder and stopper and rinse with tap water. 
    7. Repeat steps (b) to (g) for each of the other solids shown in Table 3.5
  3. For your assigned solvent, predict how much of each of the other liquids it can dissolve. Using the terms all, some, and none, record your predictions in Table 3.6.
  4. Determine the capacity of each liquid solvent to dissolve other liquids.
    1. Put 2 mL of test liquid solute into a 10 mL graduated cylinder; then fill the graduated cylinder to the 10 mL line with your solvent liquid. 
    2. Stopper the cylinder, shake the contents gently for 10 seconds, and let the mixture stand till settling stops.
    3. Observe how the solvent liquid dissolved in the test liquid. Determine how much of the test liquid dissolved.  Record your observations as all, some, or none.
    4. If there is a separation of the liquids, measure the volume of the bottom layer. Record the volume and identity of the bottom layer in Table 3.6.
    5. Wash the graduated cylinder and stopper and rinse with tap water. 
    6. Repeat steps (a) to (e) for each of the other solvents shown in Table 3.6
Table 3-4. Chemical structure of selected solutes.

Solute

Chemical Formula

Bonding

Polarity / Charged Ions

Model Molecule

Salt

NaCl

Ionic

Highly polar

 

Table Sugar (sucrose)

C12H22O11

Covalent (one glucose sugar and one fructose sugar bonded together)

Polar (due to negatively charged OH- groups)

 

Starch

(C6H10O5)n n is usually a large number

Covalent (long chains of the sugar glucose)

Nonpolar (due to branching of molecule)

 

Baking soda

NaHCO3

Ionic (compound of a covalent polyatomic ion HCO3- and Na+)

 

Charged ions

 

 

Activity Questions
  1. How do you know when:
    1. a solid has completely dissolved in a liquid?
    2. a liquid has completely dissolved in another liquid?
  2. What statements can be made about the solubility of polar, nonpolar, and ionic solutes in
    1. nonpolar liquid solvents 
    2. slightly polar liquid solvents
    3. ionic solvents
  3. Knowing that water is polar, what generalization can you make about powdered drink mix?
  4. Minerals dissolve and are carried from the land in stream water. Soil is also carried in stream water, but does not dissolve. What can you infer about minerals and soil?
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.