Freezing Point Depression — Reading Comprehension

Grades

Standards

5-PS1
MS-PS1-4
RI.6.3
RI.7.1

About This Reader

This passage, 'Freezing Point Depression,' introduces students to the physical science concept of how adding substances like salt lowers the freezing point of water. With clear examples such as icy roads, homemade ice cream, and car antifreeze, students learn how mixtures affect the freezing behavior of liquids. The concept is tied to NGSS standard MS-PS1-4, which focuses on changes in particle motion, temperature, and state. The passage highlights freezing point depression as a physical change, showing that it doesn’t alter the identity of the substance involved. Aimed at grades 5–8, the passage uses accessible language and real-world applications to engage students. It supports Common Core standards like RI.6.1 and RI.6.4 and includes 8 multiple choice questions and a science fun fact. Ideal for integrating literacy with hands-on science.

CONTENT PREVIEW

Have you ever seen salt thrown on icy roads in winter? That salt is not just for grip—it actually helps melt the ice! This happens because of a science concept called freezing point depression.

Freezing point depression occurs when a substance, like salt or sugar, is added to a liquid, usually water. This causes the liquid to freeze at a lower temperature than normal. Normally, pure water freezes at 0°C (32°F). But if you add salt, it may not freeze until it gets colder—sometimes down to -10°C or lower, depending on how much salt is added.

This happens because the added particles (like salt) get in the way of the water molecules as they try to form solid ice. It becomes harder for them to lock into the solid structure, so the water needs to get colder before it can freeze.

Freezing point depression is a physical change and an example of how mixtures can affect the properties of a substance. It doesn’t change what the water or salt is made of—it just changes how they behave when combined.

This effect is used in real life all the time:

● Road safety: Salt is spread on icy roads to lower the freezing point of water and melt ice.

● Homemade ice cream: Salt is added to ice around the ice cream container to help it freeze faster.

● Car antifreeze: Special liquids are added to water in car engines to stop it from freezing in cold weather.

Understanding freezing point depression helps us stay safe and solve everyday problems using science!

Fun Fact: The coldest temperature ever recorded on Earth was -89.2°C in Antarctica—and even there, salt water stayed liquid!

What is the main idea of the passage?

Why water boilsHow to make salt waterHow adding substances lowers the freezing point of liquidsWhy ice cream is sweet

What is freezing point depression?

The point where something boils fasterWhen a liquid freezes at a higher temperatureA change that raises the freezing point of waterA process that lowers the freezing point of a liquid

What is the normal freezing point of pure water?

100°C0°C-10°C50°F

Why does adding salt lower water’s freezing point?

It makes the water colderSalt turns into iceSalt blocks water molecules from freezing easilyWater absorbs salt and freezes faster

Which of the following is NOT an example of freezing point depression?

Using salt on icy roadsAdding sugar to teaUsing antifreeze in a carAdding salt to ice for homemade ice cream

What type of change is freezing point depression?

ChemicalReversiblePhysicalPermanent

What happens when you add more salt to water in cold weather?

It freezes fasterIt becomes hotIt freezes at a lower temperatureIt evaporates

Which best describes how salt affects ice on roads?

It makes it shinierIt keeps it frozenIt helps melt it by lowering the freezing pointIt makes the water boil