Rock Salt

The secret to less back pains

Introduction

In this flyer you will learn about what is rock salt, its alternatives, its corrosive effects, freezing point depression and expert's opinion about the topic. You will also learn why salt is used to melt snow.

Source of image: https://www.liliwood.com.br/site/img/produtos/5/-1100.jpg

What is rock salt?

Rock salt simply is like salt found in your table just in a different size because the cubes are many many times the size of a normal salt cube. The reason behind this is because the type of reaction you want to create in snow works better with more amounts of salt so the more salt you add and the bigger in size it is, the better.

Source of image: http://www.emporiumuk.biz/Images/Materials/100-CH-SAL01.JPG

What are its alternatives?

Though there are a lot, Calcium Chloride is the most common since it's cheap and accessible. The pros of it are that it's inexpensive, melts ice fast but at the cost of attracting moisture and making some surfaces slippery. Another alternative will be what's known as CMA (image below) which stands for Calcium Magnesium Acetate. The advantages of this compound are that though it doesn't do the best job at removing ice, it doesn't damage concrete and vegetation. (Helmenstine)
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What are its corrosive effects?

Everything seems to be working okay until you wake up in the morning just to see a little surprise, rust on your car... Well below you will know the reason of this.

In Finland there was a study that concluded that the concentrations of sodium in roads are affecting certain metals, such as the widely used aluminum, potassium based compounds should watch out as well as they are affected by this. This happens because potassium is an oxidizing agent.

TIP: Consider looking at alternatives because you wouldn't want your car to look like the one below over time. (Hautala)

What is freezing point depression?

Freezing point depression is the temperature of a substance affected by another substance. For example the freezing point of water is normally 32 degrees Fahrenheit (0°Celsius) but adding a substance like calcium chloride (rock salt) you could make it be as low as 2 degrees Fahrenheit (around -17°Celsius). (Scodellaro)
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What does this graph really mean?

First, let's explain what molality means, just in case if you didn't know. If you have any experience with chemistry, molality comes from the word mol so you would be guessing it has to do with moles. If you thought that then it was a good guess because it indeed involves them, good job!

The molality of a compound is a way to measure its concentration. There is a formula to know what the molality of a compound is.

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In short, the graph means that the higher the molality (concentration) of the compound sucrose, the lower the freezing point of water will go.
Source of image and information: http://www.chemteam.info/Solutions/Molality.html

What experts say...

Below there is a video featuring research from Mr. Pedro Alvarez, PhD. P.E. an expert of environmental engineering of Rice University explaining in a more visual way of what is talked above.
How Does Salt Melt Ice? - Reactions

Conclusion

Here it is, the favorite part of people who just like to scroll through stuff. In conclusion rock salt is used because of its deicing abilities though other alternatives like calcium magnesium acetate, mentioned above, work as well and have some benefits. Freezing point depression is when a substance's freezing point is altered because of the properties of another.

Works cited

  • Hautala, L., Wulff, A., & Oksanen, J. (n.d.). Annales Botanici Fennici, 179-179. Retrieved from JStor.

  • Scodellaro, M. (n.d.). Essential Experiments for Chemistry (p. 70).