K is for constant

Almost every middle and high school student has seen a chemical equation written out. When they imagine what that looks like, they probably know an equation filled with letters that have one arrow in the middle. However, most chemical equations actually have two arrows because they are equilibrium reactions. An equilibrium reaction is a reaction in which reactants and products are being created at an equal rate, hence equilibrium. This does not mean that the same amount of reactants and products are created, just that they are created at the same rate, or speed. To understand the amount of reactants and products created when a reaction reaches equilibrium, the constant, K, is used.

The equilibrium constant is determined by the ratio of the concentration of the products and the concentration of reactants. Some of the most common equilibrium constants are for acids and bases, as those are the most commonly occurring equilibrium reactions. The constant for an acid will always involve the concentration of hydrogen ions and hydroxide ions for bases. Since water dissociates into hydrogen and hydroxide, it also has a K value that remains constant at 10^-14. While K never has units, the magnitude of the number can say a lot about an equation. A very large K value means that way more products than reactants are being produced and the other way around for a small value. Given that equilibrium reactions occur everyday, in and out of the lab, understanding how they work is very important. Whether it be the air we breathe or the water we drink, almost everything is at an equilibrium.

The Spark of Fireworks

Fireworks are seen year-round and have become a staple in large-scale celebrations. New Year’s Eve and July 4th are two of the most notable examples of fireworks. The fireworks fill the night sky with bright and vibrant colors, but how do fireworks work? How do scientists know what element to use to achieve different colors? At the base of all fireworks is black powder, composed of potassium nitrate, carbon, and sulfur, which when ignited releases immense heat, causing gasses to expand and eventually send little pellets of metallic powder into the air (Brockmeier, 2019). 

As the pellets fly into the sky, the energy released by the black powder puts the electrons inside the metal into a state of “excitement.” However, atoms naturally seek to be in a state of stability, in order to revert to this state, the electrons will get rid of the excess energy by emitting wavelengths. These wavelengths present themselves as colors. Each element has distinct spacing between its energy levels. The metals that have larger spacing between the energy levels will emit shorter wavelengths, which often present themselves as blues and purples. Conversely, atoms with shorter distance between the energy levels will emit longer wavelengths which tend to be oranges and reds (Lutz, 2019). Understanding the science behind fireworks allows us to appreciate even more the bright and colorful displays that light up joyous occasions.

References: 

Brockmeier, E. K. (2019, July 1). The chemistry behind fireworks. Penn Today. Retrieved April 1, 2024, from https://penntoday.upenn.edu/news/chemistry-behind-fireworks

Lutz, A. (2019, July). Exploding Colors: The Science Behind Fireworks. The College Today. https://today.cofc.edu/2019/07/01/fireworks-fourth-of-july 

Cloud Formation

Water vapor, which is a result of evaporation, is one of the key components in the formation of a cloud. Cloud formation is a result of rising air; this occurs when the ground warms air, or when air is forced up when wind blows into the side of a terrain, such as a mountain. These two ways of air rising create different types of clouds. The former creates types including cumulus, cumulonimbus, mammatus, and stratocumulus clouds; and the latter creates lenticular and stratus clouds. Air may also rise when two large masses of air collide, giving them no choice but to go up.

In any case, rising air causes pressure and temperature to drop, making the water vapor within it condense. This occurs because as air rises, it expands due to the lower pressure. The temperature decreases at 9.8 degrees celsius per kilometer until saturation, at which the water condenses to form clouds. 

Water molecules found in the air are too small to condense on their own. Therefore, particles found in abundance in the atmosphere become the surface on which these water molecules condense, called cloud condensation nuclei. Oftentimes particles of soil, dust, pollen, salt crystals and smoke become cloud condensation nuclei. These particles are at least one micrometer and 1/100 size of cloud droplet. They also must be hygroscopic, or able to attract and absorb water from the environment. Despite these particles forming the core of each cloud droplet, clouds are still considered to be pure water. 

When more water condenses than evaporates, clouds grow. When the opposite occurs, clouds dissipate. As the atmosphere is constantly changing, condensation and evaporation are constantly occurring on cloud condensation nuclei, leading to the formation and dissipation of clouds. 

References:

Clouds and How They Form. (n.d.). University Corporation for Atmospheric Research-Center for Science Education. Retrieved March 30, 2024, from https://scied.ucar.edu/learning-zone/clouds/how-clouds-form

How Clouds Form. (n.d.). National Oceanic and Atmospheric Administration. Retrieved March 30, 2024, from https://www.noaa.gov/jetstream/clouds/how-clouds-form