Interactive heat and thermodynamics simulator
Celsius Scale
The Celsius scale measures temperature using water's fixed points: 0°C for freezing and 100°C for boiling at standard atmospheric pressure.
Interactive physics simulator
Celsius Scale Simulator
Use three real-world labs to connect Celsius readings with thermometers, water fixed points, and daily temperature examples.
What is the Celsius Scale?
The Celsius scale is a common temperature scale used in science and daily weather reports. It places the freezing point of pure water at 0°C and the boiling point at 100°C under standard atmospheric pressure.
- Uses degree Celsius, written as °C.
- Can have positive, zero, or negative values.
- One Celsius degree has the same size interval as one Kelvin.
Celsius Scale Formula
Use Kelvin in many physics formulas because Kelvin starts at absolute zero. Use Fahrenheit conversion when comparing with everyday temperature readings in countries that use Fahrenheit.
Celsius vs Kelvin vs Fahrenheit
| Point | Celsius | Kelvin | Fahrenheit |
|---|---|---|---|
| Absolute zero | -273.15°C | 0 K | -459.67°F |
| Water freezes | 0°C | 273.15 K | 32°F |
| Room temperature | 20°C | 293.15 K | 68°F |
| Water boils | 100°C | 373.15 K | 212°F |
Real-life Example
If the weather forecast says 30°C, the day is warm. In Kelvin, that is 303.15 K. In Fahrenheit, it is 86°F. The same physical temperature can be written in different scales.
Why this matters: classroom experiments often use Celsius, while many thermodynamics formulas require Kelvin.
How to Read a Celsius Thermometer
A Celsius thermometer is calibrated with evenly spaced marks. When the thermometer liquid expands upward, the top of the liquid column lines up with a temperature value. Read the value at eye level to avoid parallax error.
Solved Examples
Convert 25°C to Kelvin and Fahrenheit.
- Kelvin: K = °C + 273.15
- K = 25 + 273.15 = 298.15 K
- Fahrenheit: °F = (9/5 × °C) + 32
- °F = (9/5 × 25) + 32 = 77°F
25°C = 298.15 K = 77°F
What is the Celsius temperature of water at its normal freezing point?
- The Celsius scale is calibrated using water at standard atmospheric pressure.
- The lower fixed point is the freezing point of pure water.
- That fixed point is defined as 0°C.
Freezing point of water = 0°C
Convert -40°C to Fahrenheit.
- Use °F = (9/5 × °C) + 32
- °F = (9/5 × -40) + 32
- °F = -72 + 32 = -40°F
-40°C = -40°F
Common Mistakes
- Using Celsius directly in gas-law formulas that require Kelvin.
- Forgetting to add 273.15 when converting Celsius to Kelvin.
- Writing Kelvin with a degree symbol. Correct: 293.15 K, not 293.15°K.
- Assuming water always boils at 100°C even when pressure changes.
Quick Summary
- Water freezes at 0°C at standard pressure.
- Water boils at 100°C at standard pressure.
- K = °C + 273.15.
- °F = (9/5 × °C) + 32.
- Absolute zero is -273.15°C.
Practice Questions
1. Convert 0°C to Kelvin.
K = 0 + 273.15 = 273.15 K.
2. Convert 100°C to Fahrenheit.
°F = (9/5 × 100) + 32 = 212°F.
3. What is normal human body temperature in Celsius?
About 37°C for a healthy person, though real body temperature can vary slightly.
4. Can Celsius temperatures be negative?
Yes. Temperatures below the freezing point of water are negative on the Celsius scale.
5. What is absolute zero in Celsius?
Absolute zero is -273.15°C.
6. Which Celsius temperature has the same number on the Fahrenheit scale?
-40°C equals -40°F.
Frequently Asked Questions
What is the Celsius scale?
The Celsius scale is a temperature scale where pure water freezes at 0°C and boils at 100°C at standard atmospheric pressure.
Who invented the Celsius scale?
The scale is named after Swedish astronomer Anders Celsius. The modern form uses 0°C for freezing water and 100°C for boiling water.
What is the freezing point of water in Celsius?
The freezing point of pure water is 0°C at standard atmospheric pressure.
What is the boiling point of water in Celsius?
The boiling point of pure water is 100°C at standard atmospheric pressure.
How do you convert Celsius to Kelvin?
Use K = °C + 273.15. For example, 20°C is 293.15 K.
How do you convert Celsius to Fahrenheit?
Use °F = (9/5 × °C) + 32. For example, 100°C is 212°F.
Can Celsius temperature be negative?
Yes. Celsius values below 0°C are negative and represent temperatures below the freezing point of water.
What is absolute zero on the Celsius scale?
Absolute zero is -273.15°C. It is the lowest theoretical temperature and equals 0 K.
Is a Celsius degree the same size as a Kelvin?
Yes. A change of 1°C is the same temperature interval as a change of 1 K. Only the zero points are different.
Why is Celsius useful in daily life?
Celsius is easy to connect with water and weather: 0°C is freezing, around 20°C is comfortable room temperature, and 100°C is boiling water.
Does water always boil at exactly 100°C?
Water boils at 100°C at standard atmospheric pressure. At higher altitudes, lower pressure makes water boil at a lower temperature.
How does the simulator calculate the water state?
The simulator treats temperatures below 0°C as ice, temperatures from 0°C to 100°C as liquid water, and temperatures above 100°C as steam or boiling vapor.