The periodic table is a display of chemical elements. To make it easier for scientists around the world to study and work within the same framework, the periodic table is an international system. Even when naming elements, there has to be consistency for research to be organized on a global level. Moreover, each element on the table has an atomic number, which is based on the properties of the elements.
Simple in structure, the table is made up of horizontal rows and vertical columns. The horizontal rows are called periods. There are seven different periods and they are represented by each element’s number of outer electrons.
The vertical columns are called groups. There are 18 groups of elements and each group is either named by the first element in the group or by a Roman numeral. Known as the Alkali metals, group 1 consists of six different chemical elements. All of these metals are highly reactive and soft. Group 2, the alkaline earth metals, are also composed of six elements and have similar properties to group 1 but are less reactive. Containing some of the most commonly known elements such as Iron (Fe), Silver (Ag), Gold (Au), and Copper (Cu), are groups 3-12. These are transition metals which are harder than the alkali metals. Because they aren’t used often, groups 13-15 aren’t as important. However, group 16, the Chalcogens, are made up of four elements. Chalcogen means “ore forming” because these elements are found in metal ore. This group includes the elements oxygen and sulfur. The final group, the “noble gasses,” are classified as that since they don’t combine with other elements to readily form compounds.
Formulated by Russian scientist Dmitri Mendeleev in 1869, the periodic table is helpful and well-organized. Without it, science would be more difficult to teach and to understand.
Chemical reactions come in many forms. They can be dangerous and create explosions, but they can be helpful, too. Some chemical reactions are common, such as when a piece of firewood is burned in the presence of oxygen, it forms carbon dioxide and heat energy. Another simple reaction is the acid based reaction, one example being when an acid (like salt or vinegar) is mixed into a base (like water or baking soda). All around us in our everyday lives are chemical reactions.
There are multiple different factors that create a chemical reaction, beginning with reactants (the chemicals that go into the reaction) and products (the chemicals that result from the reaction). For a chemical reaction to be made, the equation needs to be balanced. Balancing chemical equations has to do with making sure each side of the equation is balanced between the two sides. To achieve balance, there has to be an equal amount of moles, which are the number of molecules required for a substance to have a mass equal to the AMU (Atomic Mass Unit).
Some chemical reactions are fast, and some are slow, and how long it takes is determined by the rate of reaction which is determined by concentration and temperature. For molecules to chemically react with each other, there must be a collision that is energetic enough to break the original chemical bonds.
It takes energy to break a bond and energy is released when a new bond is made. If more energy is released in the formation of the reacants’s bond, then the net effect of reaction is to release energy, often creating a violent discharge.
An oxidizing agent is a chemical that causes another to be oxidized, or to lose electrons. Rust is an example of oxidation reaction. This also happens when copper turns green or blue over time. A reducing agent is a chemical that causes another to be reduced, or to gain electrons.
Most chemical reactions are used in our everyday lives. They are fascinating and sometimes even fun to watch, but can cause fatal reactions, such as molotov cocktails, tear gas, and napalm. But without some of these reactions, life would be more difficult.
Illustration showing the Rarefactions and Compressions of a sound wave.
Sound is all around us, but few people realize what makes up a sound wave or what effect different mediums have on the waves. Sound is more interesting and complex than one would think.
Transverse Waves are what most people imagine when they think of waves. These waves are the ones used when a string is plucked or there’s a ripple in water. However, sound waves are not Transverse, but Longitudinal Waves. The velocity of any wave can be calculated by multiplying the frequency by the wavelength. Wave velocity is the distance traveled by the wave per unit time, frequency is the speed of the sound’s vibration and determines the pitch (measured in Hz), and wavelength is the distance between two identical points on a wave.
Waves have two different types of regions: Rarefactions are regions within the sound medium where molecules are more dispersed, and Compressions are regions where the molecules are clustered together. Mediums are anywhere that sound may pass through. A medium must be an area that is elastic, meaning things can be deformed and resort back to their original form. This is why sound cannot travel through outer space. Space isn’t an elastic medium, but instead a vacuum. The human ear can hear sound waves between 20-20,000 Hz. Sounds below 20 Hz are called Infrasonic and above 20,000 Hz are called Ultrasonic. Some animals can hear sounds above 20,000 and below 20 Hz.
The speed of sound depends solely on the medium through which it passes. Every medium generates a different speed for sound. For example, the speed of sound is the highest in solids, followed by liquids, and finally the lowest in gasses. The speed of sound through air is 340 m/s or 760 mph. Some jets are capable of surpassing the speed of sound by almost 10 times.
Sound waves tend to reflect or reverberate off smooth, hard surfaces, while they are usually absorbed by soft, irregular surfaces. The Law of Reflection states, “the angle of reflection is equal to the angle of incidence.” SONAR calculates how far away an object is by sending out a sound wave and then measuring the time it takes for the sound to return after being reflected. Similar to light, refraction of sound occurs when a wave continues through a medium and bends.
Forced vibrations occur when an object is forced to vibrate at a certain frequency by an input force. Resonance is similar, but not the same. Resonance occurs when objects are forced to vibrate at their natural frequency. Sound waves are pressure waves, meaning they can exert a force on objects with the help of resonance. This is the reason why sound can shatter glass. Tuning forks will vibrate and resonate off each other if they’re at the same frequency.
Interference has two types: Constructive and Destructive interference. Constructive interference is when two waves meet, combine, and increase each other’s amplitude. Destructive interference is when two waves meet, combine, and decrease each other’s amplitude.
When a sound source travels it causes the frequency of the sound it creates to be higher in the direction the object is traveling and lower in the direction opposite to the traveling object. This is why ambulances sound much louder when they’re driving towards you than away from you. When an object travels faster than the speed of sound it produces a cone-shaped shock wave. When observers encounter this shock wave they hear a Sonic Boom or crack. Sonic Booms are not the sound of the sound barrier being broken, just the noise of sound waves overlapping and being compressed into a single conical shock wave.
Sound is omnipresent, so learning about its intriguing anatomy helps us to understand our world. When it comes to the science of sounds, there is definitely more than meets the ear.
