We are running a bit behind with our Chemistry Week posts, but better late than never.
Table salt, or sodium chloride, is inexpensive and easy to obtain. It can also be used for a number of different chemistry experiments.
This video explains some background about the history and chemistry of sodium chloride.
Credit: NBC Learn and the National Science Foundation (NSF)
1. A Test for Iodide in Table Salt
- Iodized table salt
- Non-iodized table salt
- Hydrogen peroxide (be sure to use 3 %, the kind sold for home use in pharmacies)
- Corn Starch
- Tablespoon and teaspoon-sized measuring spoons
- Liquid measuring cup
- Three clear containers, such as glasses or plastic cups
- Stirring rods or spoons
- Sharpie marker, tape or other materials to label the containers
1. Label the containers: A) hydrogen peroxide + iodized salt, B) hydrogen-peroxide + non-iodized salt, and C) water + iodized salt.
2. Measure 100 mL (about 1/3 cup) of water and add it to container C. Measure 100 mL (about 1/3 cup) hydrogen peroxide (3%) and add it to container A. Next measure 100 mL (about 1/3 cup) hydrogen peroxide (3%) and add it to container B.
3. Add two Tablespoons of iodized salt to container A and stir. Add two Tablespoons of iodized salt to container C and stir. Add two Tablespoons of non-iodized salt to container B and stir.
4. Observe the containers for a few minutes. Record any changes that occur.
Check our iodine chemistry post to see what iodine looks like in water or hydrogen peroxide. Do you see anything that looks similar?
5. Now add 1/2 teaspoon of cornstarch to each container. What happens?
I love this reaction! It is quick and fairly easy to understand. Let me know if you have any questions about procedures or results.
Tom Kuntzleman has another version of this experiment with the chemistry explained. Here is his video:
2. Studying Density: Table Salt versus Salt Sense®
According to the label of the product, Salt Sense® contains real salt, but there is “33% less sodium per teaspoon.” How is this possible?
Prior to starting, answer the following questions:
What do you know about salt and its structure? How might the company achieve its claim of 33% less sodium per teaspoon? Is there 33% less chloride as well?
- Iodized Table Salt
- Iodized Salt Sense® (Available in grocery stores and online)
- Microscope or hand lens
- Petri dishes or similar shallow, clear containers
- Measuring beakers or graduated cylinders
- Kitchen scale that can weigh grams
- Laboratory notebook or paper
- Pen for recording results
1. Place a small sample of table salt in one petri dish and a sample of Salt Sense® in a second petri dish. Look at the samples under the microscope.
Draw what you see for each sample. How might the differences you observe change the amount of sodium per teaspoon?
2. Calculate the density of each substance.
Density = mass/volume
where mass is the weight of the salt in grams and volume is the amount of salt in mL.
Tare a measuring beaker on the scale (ask the instructor or read the manual if you don’t know what “tare” means.)
Pour 20 mL of table salt in the beaker. Weigh the table salt in grams and record the weight.
Now tare the second beaker. Add 20 mL of Salt Sense® to the beaker and weigh it. Record the weight in grams.
Calculate the density of each sample. Which sample is less dense? How much less dense is it?
How might you make your results more accurate?
Manufacturer Diamond Crystal’s explanation of Salt Sense®
Other experiments and activities with salt:
Grow your own salt crystals at About.com
Using salt to melt ice at NBC Learn (grades 9-12)
(Public domain photograph of salt and pepper by Jon Sullivan)