To look at salt under a microscope is one of the easiest yet most interesting scientific observations and is a great learning experience or classroom activity for students who want to understand how various materials might look when viewed through a microscope.
Salt looks different from other crystals, minerals and geometric shaped solids.
Often, this will be because salt differs in its properties when seen through a microscope, a magnifying lens or just with the naked eye.
Another reason it’s a great activity for kids is that it is extremely easy to handle and is completely safe if exposed to skin or clothing.
You can easily detect salt’s clear physical properties, like crystallisation and other various properties by looking at it through the various lenses of a microscope.
If a high powered electron microscope is used then you will even be able to analyse salt’s atomic structure.
In order to view the properties of salt more easily, the best course of action is to use either a light microscope or a digital microscope. You will need only a few simple tools and equipment for this experiment as it is a fairly simple one.
By doing this, you will be able to view any distinctive crystal formations that may occur in the salt, which will usually appear more cube-like.
But if you want to go into even more detail, you’ll need an electron microscope which will show you, in depth, the atomic structure of salt, you will even see the sodium atoms, which are much smaller than chlorine.
This article will not only take you through the method and requirements of this experiment, but will also take an in depth look at the properties of various salt types and where they come from.
This experiment can be as interesting as you make it – if you use a variety of types of salt and different samples, you will get a much more exciting result and observation!
What You Need For The Experiment
Apart from, obviously, the microscope that you’ll need to look at the structure of the salt, you will need other equipment and materials for this experiment;
- A measuring spoon, to keep the amount of salt even each time.
- A stirring rod to help dissolve the salt crystals.
- A pair of tweezers to pick up larger pieces of salt, such as cubes.
- Various microscope slides and coverslips for each different type of salt.
- Different types of salt to compare with and to keep the experiment interesting.
- Warm water to dissolve the salt in.
- A beaker for each different type of salt, so as not to contaminate the experiment.
To Prepare The Samples
While it is easy to simply place some grains of salt onto a microscope slide and just take a look under the microscope, it will improve the overall result of the experiment if the salt you are using is prepared to make it contrast better under the light of the microscope.
You can do this a number of ways, but the best is to use the following steps to improve transparency and contrast;
- Make sure to label all beakers according to which type of salt you will be pouring into it.
- Then, pour an equal amount of water into each beaker, adding a tablespoon of salt to each.
- Stir the new solution until most of that 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.
Taking care in these next steps is crucial as looking at coarse substances, such as the salt we’re using in this particular experiment, on a microscope can lead to scratching and damaging the microscope’s lens, if not completely careful.
So, to avoid this, it is best to make the samples as flat, and therefore even, as possible. Make sure to use a coverslip and be very gentle when lowering and changing lenses, this will lower the risk of any chipping or scratching from your samples.
You might be asking yourself if this experiment is even worthwhile, or exciting enough to use in an educational setting, but the reason this experiment is so great as a student activity is.
Because not only can you observe the various properties of salt crystals but also gain knowledge and experience in preparing specimen solutions.
Some key questions that will be answered in this experiment are; Where does salt come from?What is salt made up of and what can it be used on?
Why does salt form a crystal lattice and how can we view that formation properly? In the next part of the article, you will find a handy guide on how to answer these questions and give you all the information that you will need on salt!
These may seem like pretty basic questions as surely we all know that salt is a kitchen ingredient, used most often in food to make it taste more savoury and seasoned.
But, there is actually a greater depth to salt than being just a kitchen herb. Salt is quite a general term that refers to a chemical compound that has an ionic organisational structure of both positively and negatively charged ions, known as cations and anions.
These ions are usually formed by a particular combination of some acid as well as a base.
There are various organic and inorganic types of salts and these are classed as either strong or weak salts when talking about electrolytes, and acidic salt, alkali salt, or neutral salt when talking about acidity and basicity.
Salt will often have a high melting point and is very soluble in water. Salt, alongside other polar solvents, is excellent at conducting electricity and often are completely odourless too.
They can appear either transparent or white in colour and can taste sweet, sour, savoury or even bitter. Most are poisonous, with the exception of monosodium glutamate, which is used as a seasoning!
The Properties Of Common Table Salt
The most common type of salt and the one we all use in the kitchen, is a type of ionic compound that consists of both sodium and chlorine atoms.
The chemical formula is NaCl. The specific molecules of sodium chlorine create an atomic lattice by coming together in a cube shaped pattern to form individual salt crystals.
There are actually several different types of common table salt, whose natural form is rock salt or halite.
Though a few kinds of salt are produced naturally, like sea salt, that has some small trace amounts of different minerals like 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.
Common table salt forms from a crystalline mineral that you will mainly find present in seawater – thus why it is known as ‘saltwater’. On average, the ocean has a salinity of 3.5%, which means it has about 35 grams of solid salt per every litre of seawater.
However, more refined table salt usually comes from freshly mined salt, which gets harvested from prehistoric seas and then goes through a process of refining by purification and then dissolution and precipitation.
Finally, the salt will then be re-evaporated into individual crystals again.
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.
Where Can Salt Be Used?
While the main use of salt is as a staple ingredient in flavouring our food, salt can be used for much more than that too, for example it can be used for processing and even preserving food.
Salt has many industrial uses and these include the production of paper and plastic, as well as, if conditioned properly, de-icing roads and motorways.
Salt is also regularly used in various types of agriculture, mainly it is used to stop plants from growing on soil and it is also used in many cultural traditions and religious ceremonies.
It cannot be denied that it is an essential resource that is used all over the world and has both founded civilizations and caused the very wars that destroyed them.
Often, in the most famous and historic civilizations,like the ones formed in ancient Rome, Greece, Egypt, India and China, salt has been a prized possession that is not only important for trade but an actual form of currency and often used to barter with.
Salt was also known to be used in ceremonial displays and funeral offerings.
The Different Types Of Salt
While most people might only know about edible table salt as it is the most common, there are actually many kinds of salts, this kitchen salt is also somewhat of a category on its own, since there are so many different types of salt that can be used as an ingredient in the kitchen.
There are generally twelve main types of kitchen salt, all with varying shapes, sizes, colours, and even, to a certain extent, taste. Here’s what they are and how they differ:
Common Kitchen Salts
- Table salt– this is by far the most common type of kitchen salt and is harvested straight from underground salt deposits, treated with anti-caking agents, fortified with iodine, and refined to a white powdery texture.
- Kosher salt– Can be identified from its white, flaky, and coarse grained texture. This salt is used for koshering meat and is kosher salt, which dissolves quickly and releases a burst of flavour on the meat and other various kinds 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 flavour.
- 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 flavour 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 ageing.
- 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 flavour 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 flavours 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 savoury food.
- Celtic sea salt– a special type of sea salt rich in minerals and appearing as greyish chunks of moist grains is the Celtic sea salt or grey 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 flavour that makes it suitable as a finishing salt.
- Black Hawaiian salt– packed with activated charcoal that gives it a black colour 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.
Ever since I was a little girl, I have been fascinated by science. Every holiday I would ask for the newest science kit, and spend weeks learning with it.
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