Temperature is a physical quantity that allows us to measure the level of thermal energy in an object or substance, through the average kinetic energy of its particles. In simple terms, the greater the energy of movement in the particles, the higher the temperature; conversely, the less movement, the lower it will be. Thus, temperature helps us to scientifically describe what we perceive as heat or cold.
To measure temperature we use thermometers, which are calibrated on different scales, the most common being Celsius, Kelvin, and Fahrenheit. In the International System, the official unit is the kelvin (K), which defines absolute zero, the point where the movement of particles would practically stop. In addition, degrees Celsius (ºC) are used in many contexts, and in English-speaking countries, degrees Fahrenheit (ºF).
Below, we will see some examples of temperatures, which will help us better understand how this magnitude behaves in different contexts, from nature to the everyday environment.
1. Freezing point of water
The freezing temperature of the water is 0 degrees Celsius (ºC), 273 kelvin (K), and 32 degrees Fahrenheit (º F).
However, these data may vary slightly depending on the pressure to which it is subjected and the impurities it may contain.
At the same time, ice turns into water where the temperature matches the freezing point.
2. Example in the human body
The normal body temperature for humans is considered to be about 36.8 degrees Celsius (ºC).
Numerous studies have been conducted on this subject and, depending on the sources, various possible “normal” temperatures have been indicated. Recent studies indicate a temperature of between 35 and 36.9 °C, with some individual variability.
3. Boiling point of water
The boiling point of water at sea level is 100 degrees Celsius (ºC). At this level, the pressure is one atmosphere.
This record may vary if the pressure or purity of the water varies.
The boiling point is the temperature at which an element or chemical compound changes from the liquid to the gaseous state, under certain pressure conditions.
4. Temperature in the core of the Sun
The temperature at the solar core is 15,700,000 kelvin (K).
The solar core is the innermost part of the Sun and, consequently, has the highest temperature level. Within it, nuclear fusion reactions take place, responsible for the production of the Sun's energy, its brightness, and, ultimately, the sustenance of life on Earth.
5. Example in the Earth's core
The Earth's core is at a temperature of over 4,000 ºC, 4237 K, or 7,232 ºF.
The core is believed to consist of an alloy of iron and nickel with an admixture of other siderophile elements. The depth of occurrence is 2900 km. The mean radius of the sphere is 3500 km.
6. Refrigerator temperature
The ideal temperature for the refrigerator is 3°C (37.4°F), which helps keep food fresh and slow the growth of bacteria without freezing products. Maintaining this temperature reduces the risk of waste and preserves the quality and flavor of food for longer.
In the freezer, the recommended temperature is -19°C (-2.2°F), ideal for long-term preservation. At this temperature, microbial activity stops almost completely, allowing products to be stored safely for months without affecting their quality.
7. Melting point of steel
Steel melts at a temperature of around 1375ºC.
However, this melting point depends on the type of alloy and its composition. The melting point of iron is 1510 °C in its pure state, which is its main component.
Other examples of temperature
Here are some interesting cases of temperatures in different contexts:
- Liquid nitrogen: This is found at around -196 ºC (-321 ºF or 77 K). Used in cryogenics, it allows biological samples to be preserved for long periods since its extreme coldness freezes them almost instantly.
- Volcanic lava: It can be between 700 and 1200 ºC, depending on the type of volcano and magma. Although it is dangerous, when it cools it creates new layers of rock on the Earth's surface.
- Winter in Antarctica: The lowest temperature recorded on Earth was -89.2 ºC (-128.6 ºF) in 1983. In these extreme conditions, prolonged exposure can lead to hypothermia and frostbite.
- Paper Combustion: Paper begins to burn at about 451 degrees Fahrenheit (233 degrees Celsius), a figure popularized in the novel "Fahrenheit 451." This value is important in fire safety.
- Lighter flame: Reaches around 1,970 ºC (3,578 ºF), making it easy to ignite common materials thanks to the combustion of gases such as butane.