Understanding Temperature Conversion in Physics: Celsius to Kelvin

In the field of physics, understanding temperature conversion between different scales is crucial. One such conversion is from Celsius to Kelvin, which is particularly important in scientific experiments and educational settings. Let's delve into a common misunderstanding involving a Grade 7 student who attempted to boil water and explore the correct method to convert temperatures from Celsius to Kelvin.

Experiment Recap: Boiling Water in Sufuria

A recent mock experiment in a Grade 7 class involved a student attempting to boil water in Sufuria, aiming to raise its temperature from 22°C to 107°C. The temperature was then converted into Kelvin to demonstrate the difference between scales. However, it is important to recognize that it is not possible to boil water in an open vessel to 107°C; the maximum achievable temperature is 100°C. Water boils at 100°C (at standard atmospheric pressure), and boiling occurs when the water reaches its boiling point at that pressure. Any temperature above 100°C (212°F) would result in superheated steam rather than liquid water.

Boiling Point and Atmospheric Pressure

The boiling point of water is significantly influenced by atmospheric pressure. At sea level, where the atmospheric pressure is approximately 1 atmosphere (101.3 kPa), water boils at 100°C. In areas with higher atmospheric pressure, like Sufuria, the boiling point of water is slightly higher, and in areas with lower atmospheric pressure, such as high mountains, the boiling point is lower. This principle is why the experiment in Sufuria is not anomalous but rather a reflection of the environmental conditions.

Converting Temperature from Celsius to Kelvin

Converting a temperature from Celsius to Kelvin is straightforward. The Kelvin scale is an absolute temperature scale that starts at absolute zero, the point at which all thermal motion ceases. The relationship between Celsius and Kelvin is such that the size of the degree in both scales is the same. This is why a 85°C rise in temperature, as calculated in the original experiment, is also 85 K when converted to Kelvin.

To convert from Celsius to Kelvin, simply add 273.15 to the Celsius temperature. For example, the Kelvin equivalent of 22°C is 295.15 K (22 273.15). Similarly, the Kelvin equivalent of 100°C, the boiling point of water, is 373.15 K (100 273.15).

Correct Calculation for the Experiment

The rise in temperature from 22°C to 100°C in Celsius is:

$$Delta T_c 100 - 22 78^circtext{C}$$

Since the size of the degree is the same in both scales, the rise in temperature in Kelvin is also 78 K.

Conclusion

Understanding temperature conversion between Celsius and Kelvin is essential for accurate scientific measurements. While the hypothetical experiment in Sufuria involved boiling water at an unrealistic temperature, the concept of converting degrees is universally applicable. By adding 273.15 to a Celsius temperature, one can easily convert it to the Kelvin scale, ensuring accurate and reliable results in any physical measurement.

Key Points

Water boils at 100°C (at standard atmospheric pressure) and at approximately 373.15 K. The size of the degree in Celsius and Kelvin is the same, making conversion straightforward. To convert from Celsius to Kelvin, add 273.15 to the Celsius temperature.

For further reading and more information on temperature scales, explore related resources and educational materials.