In everyday science, on the Celsius scale, what temperature is commonly considered the freezing point of pure water at standard atmospheric pressure?

Introduction / Context:
The freezing point of water is one of the most familiar reference temperatures in everyday life and in basic science. It is used to define the zero point of the Celsius scale and is important in weather reports, cooking, and physical experiments. This question asks you to identify the Celsius temperature at which pure water freezes under standard atmospheric pressure, which is a key fact in school level physics and chemistry.

Given Data / Assumptions:

• The temperature scale considered is degrees Celsius.
• The substance is pure water, not a solution with dissolved salts or impurities.
• Pressure is approximately one atmosphere, the standard pressure used to define boiling and freezing points.
• We are looking for the temperature at which liquid water and ice coexist in equilibrium.

Concept / Approach:
By definition, the Celsius scale was originally set such that the freezing point of pure water at one atmosphere is 0 degrees Celsius and the boiling point is 100 degrees Celsius. These fixed points define the scale. When water cools to 0 degrees Celsius under standard pressure, it can begin to change state from liquid to solid, and the temperature remains near this value until the phase change is complete. This temperature is therefore considered the freezing point of water on the Celsius scale.

Step-by-Step Solution:
Step 1: Recall the two standard reference points of the Celsius scale: freezing and boiling of water at one atmosphere. Step 2: Note that boiling of water corresponds to 100 degrees Celsius. Step 3: Recognise that the lower fixed point, where liquid water becomes ice, is defined as 0 degrees Celsius. Step 4: Confirm that this value applies to pure water under normal atmospheric pressure without dissolved salts. Step 5: Select 0 °C from the options as the temperature commonly considered freezing.

Verification / Alternative check:
Weather reports often mention 0 degrees Celsius as the point where roads may become icy and snow can form. Laboratory thermometers calibrated in Celsius show ice water mixtures stabilising at around 0 degrees Celsius, confirming this fixed point. Conversion formulas between Celsius and Fahrenheit also point out that 0 °C equals 32 °F, which is the freezing point of water in that scale. These everyday references confirm that 0 °C is the correct value for the freezing point of pure water at one atmosphere.

Why Other Options Are Wrong:
100 °C is the boiling point of water at one atmosphere, not the freezing point. A value of -10 °C is below the freezing point and corresponds to ice that is colder than the phase change temperature. 32 °C is a warm temperature well above room temperature, not associated with freezing. A temperature of 273 °C is extremely hot and corresponds to about 546 K, far above water boiling conditions, not freezing. None of these values correctly represent the standard freezing point on the Celsius scale.

Common Pitfalls:
Some students confuse Fahrenheit and Celsius scales and remember 32 from the Fahrenheit freezing point, leading them to choose 32 °C by mistake. Others mix up the roles of 0 °C and 100 °C, forgetting which corresponds to freezing and which to boiling. To avoid confusion, memorise that 0 °C is the cold point (freezing) and 100 °C is the hot point (boiling) for pure water at one atmosphere in the Celsius scale.

Final Answer:
On the Celsius scale, the freezing point of pure water at standard pressure is 0 °C.