The physical phenomena are those events or events where the composition of the material does not change, that is, it maintains its physical properties. The chemical phenomena they are those events that happen due to changes in the composition of matter.
We achieve physical and chemical phenomena in our everyday life, from boiling water, frying an egg to the blue color of the sky. Physics and chemistry are the sciences that allow us to explain all these phenomena.
|Physical phenomena||Chemical phenomena|
|definition||Events that occur without affecting the molecular composition of matter.||Events that take place due to changes in the molecular structure of matter.|
The compounds remain the same
New compounds are produced
What are physical phenomena
Physical phenomena are events that occur in nature in which the composition of matter does not change. These phenomena can be explained by the laws of physics. Below are some examples of physical phenomena.
The sound barrier is a acoustic physical phenomenon result of the collision of sound waves in the air. Sound is a wave that travels through the air at a speed of 343 meters per second. When an airplane exceeds this speed there is a noise similar to an explosion. This is known as “breaking the sound barrier”.
The rainbow is one luminous physical phenomenon that we can observe in the sky when the light of the Sun is reflected and refracted in the raindrops. The water drops act in this case like a prism, separating the colored bands that make up the light.
A mirage is a optical physical phenomenon which occurs because light bends when crossing layers of air with different temperatures. It is an optical illusion that makes us perceive the presence of water from afar, which is not real.
Optical fibers are one optical physical phenomenon which is characterized by light traveling through long glass or plastic cables or fibers. This happens because light is reflected internally in the cable, causing it to bounce around the entire fiber without being lost to the external environment. They are widely used for the transmission of data, images and sound.
You may also be interested in learning about reflection and refraction of light.
The flashes or rays are electromagnetic phenomena that occur in the atmosphere. These are electrical discharges that usually occur during storms. This is due to a separation of electrical charges between the earth’s surface and the clouds. When lightning occurs, such a large amount of energy is released that it lights up the sky and generates heat.
What are chemical phenomena?
Chemical phenomena are the events that occur when the composition of matter is altered. In everyday life we come across different chemical phenomena that sometimes go unnoticed. Below are some examples of chemical phenomena.
Fireworks are chemical phenomena that occur by heating metals in an explosion. For example, strontium produces a deep red color, sodium produces a yellow color, copper produces a green color, and potassium produces a purple color.
Rust is a chemical phenomenon that we find in iron materials or other metals as a result of oxidation and reduction reactions. This phenomenon involves the chemical transformation of iron to iron oxide in the presence of oxygen, either from air or water, with the characteristic light brown color.
The ozone hole is the result of the depletion of ozone levels (O3) in the atmosphere, by chemical reaction with compounds known as chlorofluorocarbons (CFCs). The O3 is a molecule found in the atmosphere that protects the planet against ultraviolet rays from the Sun.
CFCs are compounds initially used as refrigerants and in aerosols. Once in the air, CFC reacts with oxygen and ozone disappears. The atmosphere at the level of the Antarctic region has the lowest concentration of ozone, which is popularly known as the ozone gap.
Acid rain is a chemical phenomenon resulting from increased acidity in rainwater due to air pollution. Industrial processes produce gaseous sulfur dioxide, which reacts with rainwater to form sulfuric acid, a strong and highly corrosive acid.
Another polluting gas is nitrogen oxide (IV) which reacts with water to form nitrous acid (HNO)2) and nitric acid (HNO3).
Acid rain has harmful effects on the environment:
- Alteration of the pH of aquatic environments.
- Dissolution of minerals.
- Corrosion of metals and constructions.
Color of hydrangeas
The color of the hydrangea sepals (Hydrangea macrophylla) is a chemical phenomenon product of soil pH:
- In acid soils (less than 7): the sepals are blue.
- In basic soils (greater than 7): the sepals are pink/purple.
This is due to the solubility of aluminum in water at acidic pH, which allows the absorption of this element by plants. As a result, aluminum binds to the anthocyanin pigment in the sepals producing the blue color.
At neutral pH (7) or basic (greater than 7) aluminum is insoluble in water, so it cannot be absorbed by plants. In this way, the color of the hydrangea sepals depends on anthocyanin which is naturally a purple pigment.
You may be interested in seeing Natural Phenomena.
Commons, C., Commons, P. et al. (2016). Heinemann Chemistry 1. 5th edition. Pearson Australia.
Ito, D., Shinkai, I., Kato, I., Kondo, T., Yoshida, K. (2009). Chemical studies on different color development in blue- and red-colored sepal cells of Hydrangea macrophylla. Biosci.Biotechnol. Biochem. 73: 1054-1059.
Ozone Hole 2015 (sf). NASA earth observatory. Retrieved from: https://earthobservatory.nasa.gov/images/86869/ozone-hole-2015