Question

Of the three temperature scales, which can have negative temperatures? For the one(s) that can't, explain why not.

Short answer

Both Fahrenheit and Celsius temperature scales can have negative temperatures, such as -40°F and -40°C, respectively. However, the Kelvin scale cannot have negative temperatures because it is an absolute temperature scale that starts from absolute zero (0 K), which is the lowest possible temperature.

Step-by-step solution

Identify the temperature scales

There are three common temperature scales: Fahrenheit (°F), Celsius (°C), and Kelvin (K).

Explore the Fahrenheit scale

The Fahrenheit scale has a zero point at -459.67 °F, representing absolute zero. This means that the Fahrenheit scale can have negative values, like -40 °F, which is also -40 °C.

Explore the Celsius scale

The Celsius scale has a zero point at -273.15 °C, which is the temperature of absolute zero. Negative temperatures are possible in the Celsius scale, with an example being -40 °C, as we have mentioned in the previous step.

Explore the Kelvin scale

The Kelvin scale has a zero point at 0 K, which is the temperature of absolute zero. Since absolute zero is the lowest possible temperature, the Kelvin scale does not have any negative temperatures.

Explain why Kelvin scale can't have negative values

The Kelvin scale is an absolute temperature scale, which means it starts from absolute zero (0 K). Since absolute zero is defined as the lowest possible temperature, it is not possible for temperatures to have negative values on the Kelvin scale. In conclusion, both Fahrenheit and Celsius scales can have negative temperatures, while the Kelvin scale cannot due to its absolute nature starting at absolute zero (0 K).

Key concepts

Fahrenheit Scale

The Fahrenheit scale is one of the most commonly used temperature scales, particularly in the United States. It was developed by Daniel Gabriel Fahrenheit in the 18th century. The scale is based on two fixed points: the freezing point of water at 32°F and the boiling point at 212°F. The scale divides the range between these two points into 180 equal parts.
Notably, the Fahrenheit scale can have negative temperatures. This means temperatures lower than the freezing point of water. An interesting point to consider is that -40°F is actually equal to -40°C. This is one of the rare points where the Fahrenheit and Celsius scales intersect and represent the same temperature.
The ability of the Fahrenheit scale to display negative temperatures makes it possible to easily express temperatures below freezing, which is often necessary in many climates. Understanding these temperature points is crucial in many scientific and day-to-day applications.

Celsius Scale

The Celsius scale, also referred to as the centigrade scale, is the standard temperature scale in most parts of the world. Developed by the Swedish astronomer Anders Celsius in the 18th century, this scale is defined by two major points: the freezing point of water at 0°C and the boiling point at 100°C. This separation into 100 intervals provides a straightforward system for scientific calculations.
Similar to the Fahrenheit scale, the Celsius scale allows for negative temperatures. This occurs naturally in climates where temperatures can get below the freezing point of water. For instance, -20°C is often seen in winter climates.
This scale's straightforward nature makes it highly useful in scientific contexts, focusing on critical physical states of water to establish its range. Its compatibility with the Kelvin scale also facilitates work in scientific fields that require absolute temperature measurements.

Kelvin Scale

The Kelvin scale is an absolute temperature scale, making it unique compared to the Fahrenheit and Celsius scales. Developed by William Thomson, also known as Lord Kelvin, this scale starts at absolute zero (0 K), the theoretical point where particles in matter stop moving entirely. Because of this, the Kelvin scale is critical in scientific research where precision is necessary.
One of the key characteristics of the Kelvin scale is that it does not have negative numbers. This is because 0 Kelvin is defined as absolute zero, the lowest possible temperature according to the laws of thermodynamics. There is no temperature lower than this, thus, making the Kelvin scale not only absolute but practical for scientific calculations involving heat, energy, and thermodynamic behaviors.
The direct correlation between the Kelvin and Celsius scales can often be observed in scientific equations, as both scales increase incrementally in the same way, with 0°C equating to 273.15 K. This allows scientists to transition effortlessly between ordinary and absolute temperature measurements.