Boiling Point - Definition, Examples, Facts & Quiz, FAQ, Trivia

Discover when liquids transform into gases at specific temperatures

Educational Standards

NGSS: 5-PS1-1, 5-PS1-3, MS-PS1-4 | Common Core: RST.6-8.3, RST.6-8.7

Learning Sections

What is Boiling Point? Factors Affecting Boiling Water Boiling Point Boiling in Daily Life Boiling Point Quiz FAQs Science Trivia

What is Boiling Point?

illustration showing water boiling in a pot with bubbles forming. Include a thermometer showing 100°C (212°F). — Water boiling at 100°C (212°F)

Boiling point is the specific temperature at which a liquid turns into a gas. This happens because the molecules gain enough energy to break free from the liquid and form bubbles of vapor.

Key facts about boiling point:
• Every liquid has its own boiling point
• For pure water, boiling point is 100°C (212°F) at sea level
• Boiling is a physical change, not chemical
• Adding substances to a liquid can change its boiling point

Think of boiling point like a special temperature threshold. When the temperature reaches this point, liquids transform into gases!

Key Concept

Boiling point is the temperature where a liquid changes to gas throughout the entire substance. This change happens because molecules gain enough energy to overcome atmospheric pressure.

Below Boiling Point

Liquid state
(Water)

At Boiling Point

Phase change occurs
(Water ↔ Steam)

Above Boiling Point

Gaseous state
(Steam)

Factors Affecting Boiling Point

illustration comparing boiling water at sea level and at high altitude. Show different thermometer readings and bubble sizes. — Altitude affects boiling point

Several factors can change a substance's boiling point:

Atmospheric Pressure:
• Lower pressure lowers boiling point
• At high altitudes, water boils at lower temperatures
• At Mount Everest, water boils at 70°C (158°F)

Impurities:
• Adding substances usually raises boiling point
• Salt water boils at higher temperature than pure water
• This is called boiling point elevation

Molecular Structure:
• Stronger molecular bonds mean higher boiling points
• Water has higher boiling point than alcohol

A Altitude

For every 300m increase in altitude, boiling point decreases by about 1°C

P Pressure

Higher pressure raises boiling point (used in pressure cookers)

S Solutes

Adding salt raises water's boiling point by about 0.5°C per 30g per liter

M Molecules

Larger molecules with stronger bonds have higher boiling points

Boiling Point of Water

illustration showing water boiling at different pressures: sea level (100°C), mountain (90°C), and pressure cooker (120°C). — Water boiling at different pressures

Pure water boils at exactly 100°C (212°F) at sea level. But this temperature changes depending on:

Factors affecting water's boiling point:
• Altitude: Higher altitude lowers boiling point
• Impurities: Salt or sugar raises boiling point
• Pressure: Higher pressure raises boiling point
• Container: Smooth containers prevent bubbling over

Did you know that bubbles form during boiling because vapor forms inside the liquid? At boiling point, vapor pressure equals atmospheric pressure.

💧

Liquid Water

Below 100°C (212°F)

Molecules close together

💨

Water Vapor

Above 100°C (212°F)

Molecules spread far apart

Superheating

Pure water in a very smooth container can sometimes be heated above its boiling point without boiling! This is called superheating. When disturbed, it suddenly boils violently.

Boiling in Daily Life

Understanding boiling point helps us in many daily activities:

Cooking:
• Boiling water cooks food faster
• Pressure cookers raise boiling point to cook food quicker

Sterilization:
• Boiling kills bacteria and microorganisms
• Medical instruments are sterilized by boiling

Power Generation:
• Power plants boil water to create steam that turns turbines

Distillation:
• Different boiling points allow separation of mixtures
• Used in producing purified water and alcoholic beverages

Cooking

Boiling is a fundamental cooking method used worldwide

Sterilization

Boiling water for 1 minute kills most pathogens

Industry

Steam from boiling water powers turbines for electricity

Science

Distillation separates substances based on boiling points

Boiling Point Quiz

Test your knowledge of boiling point with this 5-question quiz. Choose the correct answer for each question.

1. What is the boiling point of pure water at sea level?

0°C (32°F)

100°C (212°F)

37°C (98.6°F)

50°C (122°F)

2. What happens to water's boiling point at high altitudes?

It increases

It decreases

It stays the same

It becomes unpredictable

3. How does adding salt affect water's boiling point?

Lowers it

Raises it

No effect

Makes it boil faster

4. Why do pressure cookers cook food faster?

They decrease boiling point

They increase boiling point

They filter impurities

They add nutrients to food

5. What is the state of water above 100°C at sea level?

Solid ice

Liquid water

Water vapor (gas)

Plasma

Excellent! You've shown great understanding of boiling point!

Good effort! Review the boiling point facts and try again.

Frequently Asked Questions

Here are answers to common questions about boiling point:

Why does water boil at lower temperatures at higher altitudes?

At higher altitudes, atmospheric pressure is lower. Since boiling occurs when vapor pressure equals atmospheric pressure, water reaches this balance at a lower temperature. This is why cooking times are longer in mountains.

Why do bubbles form when water boils?

Bubbles form because water at the bottom of the container turns to vapor. As this vapor rises, it forms bubbles that grow and eventually rise to the surface. The bubbles contain water vapor, not air.

Can water get hotter than its boiling point?

Under normal conditions, liquid water can't exceed 100°C at sea level because it turns to vapor. However, in a pressure cooker or with superheating, water can temporarily exceed this temperature before boiling violently.

Why does salt raise the boiling point of water?

Salt dissolves into ions that disrupt water molecules, making it harder for them to escape as vapor. This means more energy (higher temperature) is needed for vapor pressure to equal atmospheric pressure.

Science Trivia

Discover amazing facts about boiling point:

Highest Boiling Point

Tungsten has the highest boiling point of all elements at 5555°C (10031°F)! It's used in light bulb filaments and rocket engines.

Lowest Boiling Point

Helium has the lowest boiling point at -268.9°C (-452°F)! It remains liquid at temperatures close to absolute zero.

Pressure Cooking

Pressure cookers raise boiling point to about 120°C (248°F), reducing cooking time by up to 70% and preserving more nutrients.

Geothermal Boiling

In Yellowstone's geysers, water boils at just 93°C (199°F) due to high altitude. Old Faithful erupts when boiling water turns to steam underground.

Related Resources

The Boiling Point of Water

This passage, 'The Boiling Point of Water,' introduces students to the physical property of boiling ...