The Celsius and Kelvin scales are both really important for measuring temperature in physics.

Celsius Scale:

• This scale uses the freezing point and boiling point of water to measure temperature.
• The freezing point is 0°C, and the boiling point is 100°C.
• For example, if you have ice at 0°C and you heat it up, when it gets to 100°C, it will start to boil!

Kelvin Scale:

• This scale is mostly used in science.
• It starts from something called absolute zero. This is the point where atoms move the least, and it's 0 K.
• Changing Celsius to Kelvin is easy! You just add 273.15.
• So, if it’s 25°C, you would do $25 + 273.15 = 298.15$ K.

In short, the Celsius scale is about how water behaves, while the Kelvin scale is about the absolute temperature. This is really important for scientific calculations!