Lab: Properties of Ionic and Covalent Compounds Procedure
TEST ONE: Solubility in Solution
Solubility in water(polar solvent): Record your findings in the Data Section for all of your observations.
1.
2.
3.
4.
Place one scoopula full of each compound in a small beaker and add about 20 mL of
deionized water
Stir gently with a stirring rod for at least 20 seconds, wiping off the stirring rod in
between solutions in order to not mix the solutions.
If most of the solids have dissolved, it is considered soluble
You will be using these solutions for your conductivity test, so ***DO NOT pour them
out.
TEST TWO: Conductivity in Solution
1.
Using the conductivity tester that has been provided submerge the electrodes in each of your
solutions of water from part one. Be sure to rinse the aluminum coated electrodes in deionized
water between every test
2.
Record your observations in the data table as you go.
3.
Dispose of each solution properly, clean and dry each beaker before continuing to part three.
4.
Rinse and dry the conductivity tester
***DO NOT pour the paraffin wax solution down the sink, dispose of this in the aqueous waste
container. Everything else can be disposed of down the sinks.
TEST THREE: Relative Melting Point Determination
1.
Place the aluminum foil on the ring stand and loosely wrap the edges around
the ring stand, as shown in Figure 1.
2.
Adjust the ring stand so that it is about 2 fists above the bunsen burner.
3.
Using a scoopula, obtain a pea-sized sample of of each substance you are testing.
Place the samples separate from one another on the aluminum foil. See Figure 2.
4.
Light the bunsen burner and make sure the Bunsen burner flame is directly below
the center of the aluminum square.
5.
Make your observations and record the relative melting points
*Note: Have someone at the table record the time. The flame should be shut off
between 20-60 seconds
TEST FOUR: Flame Test
1.
2.
3.
Obtain a soaked stick from the supplies table in the center of the classroom. *Do not get them
mixed up. Hold it over the lit bunsen burner and record your observations. (You will be needing 3
sticks; 1 for each test)
Is a color produced? What about an odor?
Throw the sticks in the disposal beaker on the cart and repeat with the other two substances.
PART 2: Testing the unknowns- See Part 2 of your lab for scenario and further instructions.
TEST FIVE: Procedure
1.
Repeat parts 1-4 to determine the identity of the three unknowns.
2.
Record your data for each part in your data table
Note: For Part Two you will need to add two scoops of the unknown to each beaker of water. For clean
up, dispose of all solutions down the sink and thoroughly clean out the beakers.
*Follow the instructions thoroughly and in the same order to complete the lab. Help Ms. Gee determine
these samples!
Lab: Properties of Ionic and Covalent Compounds
Introduction: Use the following information to complete your pre-lab questions on the lab
handout.
Learning goals: In this lab you will learn some basic chemical techniques that draw connections
between an element’s chemical properties and the bond type(s) found in it. The properties we
are observing will be solubility, conductivity, melting point and flame color. You will test each
property for a variety of known and unknown substances, gather data, and then use your data
to infer the bonding characteristics of several unknown compounds.
The known compounds that will be tested in this lab are:
● Sucrose- More commonly known as sugar, is a polar covalent molecule
●
Sodium chloride- More commonly known as table salt, is an ionic compound
●
Paraffin Wax- More commonly known as candle wax used in common household wax
products is a nonpolar covalent molecule
Science Concepts:
I.
II.
Solubility: The phrase “like dissolves like” means that compounds will dissolve other
compounds with similar bond types. Water, a polar molecule, is a solvent that will
dissolve both ionic compounds and polar covalent compounds. Hexane, a nonpolar
molecule, is a solvent that will only dissolve nonpolar covalent compounds.
Conductivity of Aqueous Solution: If a solution contains an ionic compound, then it will
strongly conduct electricity, completing the circuit and lighting up the bulb. A polar
covalent compound will be a medium conductor of electricity due to the partial charges
of the molecule. A solution containing nonpolar molecules will not conduct electricity at
all (or will be extremely low).
III.
Relative Melting Point: You will not measure the exact values for the melting point. The
order in which the compounds melt will give relative melting points. If a substance melts
faster, then this would be considered a “low” melting point and if a substance does not
melt with the bunsen burner this would be considered a ”high” melting point.
IV.
Flame Test: When electrons of a cation are excited with something such as a flame, a
color is emitted. This can only be observed with ionic compounds due to the dissolving of
the ions in a solution.
NOTE: While most substances can be neatly placed in “ionic” or “covalent” categories, some
compounds share properties of both. Ions have varying degrees of positive or negative charge,
and molecules have varying degrees of polarity, from nonpolar to highly polar.
Lab: Properties of Ionic and Covalent Compounds
Prelab: Read the information from the previous pages in order to answer the following pre-lab
questions.
1.
2.
Read the information provided about the known substances we will be testing to
determine their bond type(polar, nonpolar or ionic).
a.
Table Salt (NaCl) __________________
a.
Sugar (C12H22O11) __________________
b.
paraffin wax (C15H32) _________________
Read the information provided under “Solubility” to determine the polarity of our
solvents. Circle the solvent that is NONPOLAR.
H20 (water)
C6H14 (hexane)
3. Summarize the information provided regarding the following lab techniques:
Solubility: _______________________________________________
Conductivity: ____________________________________________
Melting point:____________________________________________
Flame test:______________________________________________
4. Predict what the outcome will be for the following tests:
Compound
Salt(NaCl)
Sugar(C6H12O6)
paraffin wax
Solubility in
Water
(yes/no)
Conducts
Electricity in
Solution
(low/med/high)
Relative Melting
Point
(low/med/high)
Flame Test
(Will it produce a
color?)
Experimental Data (Part I):
- Take detailed observations of what you see and smell
Compound
Solubility in
Water
(yes/no)
Conducts
Electricity in
Solution
(low/med/high)
Relative Melting
Point
(low/med/high)
Flame test
(color change,
odor, etc)
PART 1-TESTING KNOWN COMPOUNDS
Salt
(NaCl)
Sugar
(C6H12O6)
paraffin wax
(C15H32)
Conclusion:
- Answer the following questions in complete sentences and support your answer with
your observations when asked
1.
Based on your solubility tests with salt, sugar and paraffin wax, support the statement
“like dissolves like”. Use your data to support your answer.
2.
Based on your tests with salt, sugar and paraffin wax, compare/describe the melting
points of polar, nonpolar and ionic compounds. Use your data to support your answer.
3.
A compound that conducts electricity when dissolved is called an electrolyte. What bond
type would be considered a strong electrolyte and why?
PART 2: Testing the unknowns
Scenario: So, Mrs. K was setting up your lab the other day and a baby skunk must
have snuck in the building. She was measuring out all of the lab samples when she
saw the sunk and the skunk saw her. She ran for it and straight to Mrs. McNeese’s
office. After a while, she returned back to the lab to finish setting up. She had just
finished measuring out all of the samples before the skunk situation and upon
returning she forgot which sample was which. Help Mrs. K out and test the
unknowns to determine the identity of the samples.
Here are the three samples that we need to determine the identity:
● Dextrose- More commonly known as the sugar found in our bodies, it is a polar covalent
molecule.
● Potassium chloride- Used commonly as a table salt substitute and is an ionic compound.
Potassium ions produce a beautiful lavender flame.
● Calcium acetate-The calcium ions in the bond help to control high blood levels of
phosphorus with kidney disease who are on dialysis.
Now that you know the properties of ionic, polar covalent and nonpolar covalent compounds,
use this information to help you determine the mixed up samples.
Experimental Data (Part II):
- Take detailed observations of what you see and smell
Compound
Solubility in
Water
(yes/no)
Conducts
Electricity in
Solution
(low/med/high)
Relative Melting
Point
(low/med/high)
PART 2- TESTING UNKNOWN COMPOUNDS
Unknown 1
Unknown 2
Unknown 3
4. Identify each of the unknowns:
Unknown 1: _______________
Unknown 2: _______________
Unknown 3: _______________
Flame test
(color change,
odor, etc)
Part 3: Identifying Unknowns CER
In the form of a CER, answer the question:
What is the identity of Unknown 2?
Claim: Answer the question in a complete sentence by making a claim.
Cite evidence : Only include observations from your lab that will help you support your claim.
Reasoning: Explanation of science behind your observations. Ex: Why did one compound
conduct electricity more strongly than another and how did that allow you to determine the
unknown?
Bonus: summarize to finish off your response by reiterating the original claim.
NAME: ________________________________________________
PER: _________
Section
Requirements
Possible
Points
2
Pre Lab Q1
●
●
Accurate lewis dot structure and polarity identification for water
Accurate lewis dot structure and polarity identification for hexane
Pre Lab Q2
●
●
●
Correct bond type for table salt
Correct bond type for sugar
Correct bond type for paraffin wax
●
●
●
●
Explicit, written observable solubility characteristics
Explicit, written observable conductivity characteristics
Explicit, written observable melting point characteristics
Explicit, written observable flame test characteristics
●
●
●
Four test outcomes predicted for table salt
Four test outcomes predicted for sugar
Four test outcomes predicted for paraffin wax
●
●
●
●
Goggles on, hair tied back
Station is entirely clean upon leaving (including sink)
Phones away
Stay at lab station entire class
Lab
Performance
Data Table
●
●
Five mostly accurate test outcomes for the known compounds
Five mostly accurate test outcomes for the unknown compounds
2
Lab
Performance
Analysis Q1
●
●
Description of “like dissolves like” meaning
Evidence from solubility test used
2
Lab
Performance
Analysis Q2
●
●
Relative melting points between the compounds comparison
Evidence from relative melting point test used
2
Lab
Performance
Analysis Q3
●
●
Accurate identification of bond type
Evidence to support bond type identification used
2
Lab
Performance
Analysis Q4
●
●
●
Accurate identification of unknown compound 1
Accurate identification of unknown compound 2
Accurate identification of unknown compound 3
Lab
Performance
CER
●
●
●
Claim answers the question in a complete sentence
Evidence includes at least 3 relevant observations from the lab
Reasoning explains why evidence supports the claim using scientific
concepts such as polarity and bond properties (see Bond Properties
Notes)
Pre Lab Q3
Pre Lab Q4
1.5
2
1.5
Lab Etiquette
4
2
8
POINTS EARNED: ________/29
Earned
Points