Looking at salt under the microscope is a great learning activity for young students who are exploring how different materials look like when viewed through a microscope, especially when studying crystals, minerals, and other geometric shaped solid substances.
This is because salt looks different when viewed with the naked eye, with a hand lens or magnifying glass, and with different types of microscopes. Plus, it’s also easy to source, and is safe to handle.
By viewing salt through the lenses of a microscope, one can easily see its distinct physical properties, including its crystallization, and even what it’s made of, especially if high powered electron microscopes are used, which can see the salt’s atomic structure.
How to observe salt under the microscope
An easy way to study salt is by using a light microscope or a digital microscope. Only a few tools and ingredients are needed to set up a simple yet informative activity that will showcase the different properties of various types of salt.
This should enable you to see the distinctive crystal forms of the salt, which normally appears as cubes. However, if you want to go even further, an electron microscope should show you the atomic makeup of salt, where you’ll see that sodium atoms are smaller than chlorine.
What you’ll need
Aside from the microscope that you’ll use to view the salt, here are the different materials that you will need for the activity:
- At least two or three different types of salt
- Warm water for dissolving the salt
- One beaker or jar for each type of salt
- Measuring spoon, a stirring rod, and tweezers
- Microscope slides and coverslips for each type of salt
Preparing the samples
While you can simply place a few grains of salt onto a microscope slide and view it under the microscope, it’s best if the salt undergoes a bit of preparation to alter its shape and thickness, thus increasing its transparency and contrast, which is important for light microscopes
- Label all the beakers according to which type of salt you will use it for.
- Pour equal amounts of water on each beaker, and add a tablespoon of salt each.
- Stir the solution so that most of the salt dissolves in the water.
- Set the beakers aside for several days until the water completely evaporates.
- Decant the water from the beaker, and gently scrape the salt off.
- Place a few salt crystals on a microscope slide and cover it with a coverslip.
- Carefully place the slide on the microscope stage.
Here is a magnified image of raw and unprepared salt, compared with raw and unprepared sugar, both right off the condiments rack. As you can see, some of the particles are noticeably smaller and rounder, while the others are larger and more edgy. Can you identify which is salt, and which is sugar?
Observing the samples
When using the microscope, start with the low power objective lens, and make note of what details you can see, such as the color, shape, and apparent texture of the salt crystals, then shift to the high power objective lens, and identify what details become visible.
Do this for each of the different types of salt you have prepared, and compare the difference between each one, such as the formation and size of the crystals.
You can also compare how each type of salt looks like before and after you prepare it. The prepared sample will almost always appear smaller, but also brighter and in clearer detail than the raw sample right off your kitchen cabinet.
This is a series of interesting microscope images of salt patterns created on a dried up solution, and viewed under low and high magnification objective lenses (28 and 98x). Notice the similarities and differences of the pattern on each solution.
Note: It’s important to be careful in viewing salt and other coarse substances on a microscope, since these can easily scratch and damage the sensitive objective lenses. Therefore, making the samples as flat and even as possible, using a coverslip, and carefully lowering and changing lenses is a must.
Purpose of the activity
Now, why is this even important? Well, it’s an easy and simple but highly educational activity when using microscopes to study different specimens. Not only will you be able to observe the different properties of various types of salt crystals, but you will also experience how to prepare specimen solutions.
Other than this, however, just what makes salt so great? What is it, exactly? Where does it come from, and where can it be used on? Below is an informative guide on everything you need to know about salt.
What is salt?
This may seem like a weird question, since we all know that salt is just a staple kitchen ingredient that makes food taste, well, salty. But, there is actually more to it than that. Salt is a broad term that essentially refers to a chemical compound that features an ionic organization of positively and negatively charged ions (cations and anions).
These are generally formed through a combination of an acid and a base. There are organic and inorganic salts, which can either be classified as strong salt or weak salt when talking about electrolytes, and acidic salt, alkali salt, or neutral salt when talking about acidity and basicity.
Salt generally has a high melting point, is soluble in water and other polar solvents, can conduct electricity, are usually odorless, and appears transparent or white. It can taste sweet, sour, bitter, or savory, but is mostly poisonous, except for monosodium glutamate, which is a type of seasoning.
Common table salt
The salt that we know is one of the many classes of salt. It is a type of ionic compound consisting of sodium and chloride atoms, with a chemical formula of NaCl. Molecules of sodium chloride create salt’s atomic lattice by gathering together in a cubic pattern to form a salt crystal.
There are different kinds of common table salt, whose natural form is rock salt or halite. Some kinds of salt are naturally produced, like sea salt, which has trace amounts of various minerals including potassium sulphate and calcium chloride.
There are also other types of salt that are processed in a factory and are artificially added with chemicals in order to fortify it, such as iodized table salt.
Where can you find salt?
Table salt comes from a crystalline mineral that is largely present in seawater, hence the term saltwater. The ocean has a salinity of 3.5%, which means it has about 35 grams of solid salt per every liter of seawater.
Refined table salt generally comes from freshly mined salt, which is harvested from the prehistoric seas, then refined before undergoing purification through a process of dissolution and precipitation, and finally, re-evaporated.
Apart from evaporating seawater and spring water that is rich in minerals, salt can also be harvested and processed from salt mines. This usually creates chlorine and caustic soda, with only 6% of total salt production geared for human consumption in the form of table salt.
Here is a magnified image of two different types of salt, namely, the Himalayan salt which comes from the mountains, and the Celtic sea salt which comes from the ocean. These side by side images are taken at high magnification for the purposes of spectral analysis.
Where can you use salt?
Other than serving as a staple ingredient in flavoring food, salt can also be used for processing and preserving food. Its many industrial uses include the production of plastic and paper products, in conditioning processes, and in de-icing roads and highways.
It’s also used in agriculture, mainly as a tool to prevent plant growth on soil. Salt is also used in various cultural traditions and in religious practices. It’s an essential commodity that built civilizations and caused wars.
In the past, it served as a prized possession and an important article of trade for different civilizations in Rome, Greece, Egypt, India, China, and more. Salt was used as a trading item, a form of currency, and for bartering, as well as a ceremonial seal and a funeral offering.
What are the types of salt?
While we have mentioned that edible table salt is only one of the many kinds of salts, this kitchen salt is also somewhat of a category on its own, since there are different types of salt that can be used for cooking.
Here is a collated microscope photograph of some common types of kitchen salts, including table salt, and two types of koshering salt, namely, morton kosher salt and diamond crystal kosher salt. Notice how each one is distinctively different?
There are generally twelve main types of kitchen salt, all with varying shapes, sizes, colors, and even, to a certain extent, taste. Here’s what they are and how they differ:
Common kitchen salts
- Table salt– the most common type of kitchen salt is table salt, which is harvested from underground salt deposits, treated with anti-caking agents, fortified with iodine, and refined to a white powdery texture.
- Kosher salt– a white, flaky, and coarse grained salt used for koshering meat is kosher salt, which dissolves quickly and releases a burst of flavor on the meat and other types of food.
- Himalayan pink salt– the purest form of salt is the Himalayan salt exclusively harvested from a salt mine in the Himalayan mountains, containing a variety of minerals that make it great for cooking and spa treatments. It’s off white to pink, and has a bold flavor.
- Sea salt– kitchen salt that comes from evaporated seawater is aptly named as sea salt, which appears as white unrefined and coarse grained cubes, and has a more complex flavor due to the presence of other minerals.
Special types of salt
- Kala namak– translated to black salt, kala namak is a variation of the Himalayan salt that features bigger and darker colored crystals of reddish black due to its combination with various ingredients and a delicate process of firing, cooling, and aging.
- Smoked salt– another processed kitchen salt is the smoked salt, which appears as luscious brown crystals similar to sugar rocks, is made by smoking the salt for weeks, and gives a salty and smoky flavor to hearty dishes.
- Pickling salt– a relatively pure kitchen salt is the pickling salt, which is free from minerals, iodine, and anti-caking agents, making it perfect for making pickled foods without the risk of weird flavors and unwanted discolorations.
Variations of sea salt
- Fleur de sel– the most expensive type of sea salt is the fleur de sel, which is harvested in the coasts of France during dry sunny days, has a high mineral content, appears as blue grey paper thin crystals, and is good for seasoning sweet and savory food.
- Celtic sea salt– a special type of sea salt rich in minerals and appearing as grayish chunks of moist grains is the Celtic sea salt or gray salt, which has a briny taste that’s good for seasoning fish, meat, and as a baking ingredient.
- Flake salt– also a type of sea salt, flake salt is made by evaporating seawater through boiling, which results in irregularly shaped flaky crystals with a crunchy texture and a pop of flavor that makes it suitable as a finishing salt.
- Black Hawaiian salt– packed with activated charcoal that gives it a black color is the black Hawaiian or black lava salt harvested from volcanic islands and used to season meat and seafood.
- Red Hawaiian salt– another Hawaiian salt harvested from volcanic areas, more specifically from iron rich clay, is the red Hawaiian salt, which is used in a variety of dishes and in special ceremonies.
Apart from these, there are many other specialty and regional salts, such as truffle salt, Cyprus black lava salt, pink salt from the Andes mountains, Persian blue diamond salt, sogeum salt from Korea, Antarctic sea salt, Kona deep water salt, and the Mexican sal de gusano.
Salt is a great and readily available ingredient that can be viewed under the microscope in order to learn various things relating to physical properties of crystals. It’s safe and easy to source, easy to handle and view under a microscope, and offers a lot of useful information.
There are also many different types of salt, whether for cooking or for many other purposes, and engaging in advanced methodologies of studying these salts is a fun, interesting, and educational activity.