CLASS COPY: DO NOT WRITE ON THIS PAPER
Ionic vs. Covalent Bonding Lab
Pre-lab Questions (write in your notebook):
1. How is an ionic bond formed?
2. What are two types of covalent bonds? Why do covalent bonds exist in these two different forms? Use
the word electronegativity correctly in your answer.
Objective:
 To determine which unknown substances are made of ionic bonds and which are made of covalent
bonds by testing three different properties: melting point, solubility and electrical conductivity of 3
unknown substances.
Formulate Your Lab Question:
 Use the objective of the lab today to formulate your lab question. What are you trying to figure out?
Hypothesis:
 Write your hypothesis using the correct format. Make sure to include what you will be testing and what
the outcome will be. Use the format:
o If the substance contains _________________, then it is ___________________, as measured by______________.
Materials:
 Unknowns #1, #2 and #3 in separate beakers
 3 empty 50mL beakers
 Electrical conductivity tester set up (3 alligator clips, one light bulb/LED and one battery)
 Hot plate (1 per lab table)
 Beaker of distilled water – this is your rinsing water
 Empty beaker (250mL)
 Glass stir rod with rubber stopper
 Plastic spoon
 Scotch tape to label beakers
Procedures (DO NOT COPY):
1. Turn on hot plate to medium heat.
2. Obtain the necessary materials for the lab (most are provided at your lab station).
3. Label each empty 50 mL beakers as UK (unknown) #1, UK #2 and UK #3 with your tape and sharpie.
Melting Point Test
4. Obtain a small spoonful of unknown #1, #2 and #3 and place each in their own individually labeled
50mL beaker.
5. Place each beaker on the hot plate and record how long it takes each substance to melt in your data
table (relative: slow, medium, fast). THIS IS THE POINT AT WHICH THE SUBSTANCE STARTS TO MELT!
If it never melts, the melting point is extremely high.
6. Rinse each beaker thoroughly with DISTILLED water from your rinsing beaker. Turn off hot plate.
At this point, can you tell which substances are ionic or covalent? Remember the properties
we discussed in class.
Solubility Test
7. After each beaker is rinsed with DISTILLED water, fill each beaker about halfway with DISTILLED water.
8. Add a small spoonful of each unknown #1, #2 and #3 to each individually labeled beaker. Stir one
substance at a time for 30 seconds. Rinse your stirring rod with DISTILLED water after stirring each
substance.
9. Record in your data table which unknowns are soluble (dissolved) in water.
10. Do not discard of your solutions! You will need these for the conductivity test.
CLASS COPY: DO NOT WRITE ON THIS PAPER
At this point, can you tell which substances are ionic or covalent? Remember the properties
we discussed in class.
Conductivity Test
11. Attach your alligator clips to your battery and light bulb as indicted by the image below:
You will require the use of all 3 alligator clips:
1st clip:
- Attached to battery and LED/light bulb
2nd clip:
- Attached to battery and one end free
3rd clip:
- Attached to LED/light bulb and one end free
**The two free ends will be dipped into your
solution to test if the light bulb/LED lights up or
not**
12. SOLID STATE: test the solid state of each unknown with the free ends of the alligator clips and record in
your data table whether or not they conduct electricity as indicated by the LED/light bulb lighting up.
13. DISSOLVED STATE: test the dissolved solution of each unknown substance from your previous test on
solubility. Record in your data table whether or not each substance conducts electricity as indicated by
the light bulb/LED lighting up or not.
At this point, can you tell which substances are ionic or covalent? Remember the properties
we discussed in class.
14. Rinse all glassware in the sink with tap water to save the distilled water and return materials to their
original positions on your lab table.
15. Add your data to the class data sheet at the front of the room.
Data/Results:
 Include your results on the class data sheet at the front of the room so we can compare our results and
to indicate where tests should be re-done.
 The teacher will provide the answers to what each unknown is after everyone has completed their tests.
Conclusion:
1. Restate your hypothesis and explain whether you support it or reject it based on your DATA. Use
EVIDENCE from your DATA in your explanation.
2. Explain why unknown _____ contains ionic bonds and why unknown _____ contains covalent bonds. List
each unknown and explain why it is ionic or covalent using EVIDENCE from your DATA FROM EACH
TEST and the elements involved in the bonds within the molecule.
3. What two ions does NaCl (sodium chloride = table salt) dissociate into when dissolved in water? Draw
each! Remember back to the video on ionic compounds from Wednesday!
4. In an ionic compound, ions dissociate and dissolve in water. In a covalent compound, the molecule
dissolves in water as well. Why does an ionic compound conduct electricity and the covalent compound
does not?
5. Case study:
a. When you sweat, your body produces salt on the surface of your skin. This is because the salt
attracts water molecules, which then remain in contact with the surface of your skin helping to
keep it cool. This is an action required to maintain homeostasis and prevent your body from
overheating. Imagine you have a pool full of distilled water with an electrical current running
through it. You jump in…
i. Would the water conduct electricity before you jumped in? Why or why not?
ii. Would the water conduct electricity after you jumped in? Why or why not?