Understanding the Boiling Point of Pure Water: A Key to IGCSE Chemistry

What temperature indicates pure water based on its boiling point?

• A. 0°C
• B. 50°C
• C. 100°C
• D. 150°C

Answer: (C)

The boiling point of pure water at standard atmospheric pressure (1 atm or 101.3 kPa) is 100°C. This temperature is well-established in scientific literature and serves as a definitive reference for identifying pure water. Boiling point is a critical physical property of a substance, and for pure water, it reflects the temperature at which water transitions from a liquid to a gas. The significance of boiling point in indicating purity lies in the fact that impurities typically alter the boiling point of a substance. For example, if there are dissolved salts or other substances in the water, they can elevate the boiling point above 100°C, whereas the presence of certain other impurities might cause the boiling point to decrease. Therefore, a boiling point of exactly 100°C suggests that the water is indeed pure, as no impurities have influenced its boiling behavior. In contrast, temperatures like 0°C and 50°C correspond to other states or conditions of water, such as its freezing point or part of the temperature range before reaching boiling. Similarly, 150°C is significantly higher than the boiling point of pure water at standard atmospheric pressure, indicating that this temperature would suggest either a different substance or very high-pressure conditions, further confirming that only 100°C is indicative of

When you think about chemistry, boiling points might not be the first thing that comes to mind. But if you're gearing up for the IGCSE Chemistry exam, it's like a golden nugget of knowledge you don't want to miss! So, what’s the boiling point of pure water? You guessed it—100°C! That’s right. But let's crack this open a bit more.

Why is this little number so important? Well, the boiling point is not just a random figure scribbled in textbooks. It's a definitive reference point for scientists and students alike. At 100°C and under standard atmospheric pressure, pure water makes that critical transition from liquid to gas. Pretty cool, huh?

Now, why should we care about boiling points when it comes to purity? Here's the kicker: impurities can mess with the boiling point. Imagine you're cooking up some soup on the stovetop. If you've tossed in a couple of salt crystals, the boiling point jumps above that clean 100°C. Conversely, certain other substances can drop the boiling point below it. This means a boiling point of exactly 100°C can act as a litmus test for water's purity. Pretty fascinating how chemistry encroaches into our daily life, right?

If you’re wondering about other notable temperatures—like 0°C or 50°C—these correspond to water's freezing point and parts of the temperature range leading up to boiling. A temperature of 150°C? That's another kettle of fish entirely! That temperature wouldn’t suggest pure water under normal conditions; you'd be looking at either a different substance or really high-pressure scenarios. It's all about context!

This boiling point knowledge isn’t just dry facts for your IGCSE Chemistry exam; it’s a foundational cornerstone that supports tons of other scientific principles. For instance, why do you think we even measure boiling points in the labs? After all, knowing how a substance behaves under heat gives us insights into its nature and helps us in various applications—from cooking to industrial processes.

So, as you're hitting the books and digging into your practice exams, keep this boiling point concept in mind. It's not just an isolated fact but part of a bigger picture filled with everyday applications and broader scientific significance. Knowing that pure water boils at exactly 100°C under standard pressure not only helps confirm its purity but also deepens your understanding of chemical properties. And isn’t that what chemistry is all about? Uncovering the hidden aspects of substances that interact with our world? So, keep this in your chemistry toolbox as you prepare for your exams. You'll be amazed at how often this seemingly simple fact comes into play!