The Density of Water — Reading Comprehension

Premium Resource

Grades

Standards

MS-PS1-2

About This Reader

"This NGSS-aligned science passage explains the density of water in a way that is clear and engaging for middle school students. Readers learn what density means, how it is measured, and why water behaves differently from other substances when it freezes. The passage also explores how water’s density influences ocean layers and floating or sinking of objects. Key vocabulary like thermocline, halocline, and g/cm³ is introduced in context. This reading comprehension passage is ideal for reinforcing NGSS standards, particularly MS-PS1-4, which focuses on the structure and properties of matter. The content supports classroom discussions about real-world applications, such as ship design, marine life survival, and weather systems. With a mix of scientific facts and everyday examples, this passage supports both literacy and science goals in a fun and accessible way for young learners."

CONTENT PREVIEW

Water is one of the most important substances on Earth, and its density is a key reason why it behaves the way it does. Density is the amount of mass in a given volume. It is usually measured in grams per cubic centimeter (g/cm³). The density of pure water is 1.0 g/cm³ at room temperature. This means that one cubic centimeter of water has a mass of one gram. Understanding water’s density helps scientists explain many natural phenomena.

One of the most interesting things about water is that it behaves differently than most substances when it freezes. Usually, when a liquid freezes into a solid, it becomes denser. However, water is an exception. As water cools down and turns into ice, its molecules spread out and form a structure that takes up more space. This makes ice less dense than liquid water, which is why ice floats. This floating ice acts as insulation for lakes and ponds in winter, allowing life to survive beneath the frozen surface.

Another important example of water’s density is in oceans and lakes. Water layers based on temperature and salt levels. Cold water is denser than warm water, and salty water is denser than fresh water. These differences create layers in the ocean called thermoclines and haloclines, which affect ocean currents and marine life. Scientists study these layers to understand climate patterns and the movement of nutrients in water ecosystems.

In everyday life, water’s density is important for floating and sinking. Objects that are less dense than water will float, like a wooden log or a plastic bottle. Objects that are more dense, like a rock or a coin, will sink. Engineers use this knowledge to design ships, submarines, and other floating structures.

The density of water plays a big role in Earth’s systems. It helps explain why ice floats, how oceans work, and what materials sink or float. By understanding water’s density, scientists and engineers can solve problems and design better tools.

Fun Fact: Water is one of the only substances that is less dense as a solid than as a liquid!

What is the density of water?

5 g/cm³0 g/cm³0 g/cm³0 g/cm³

Why does ice float on water?

It is heavier than waterIt traps air bubblesIt is less denseIt has more salt

What happens to water molecules when frozen?

They break apartThey shrinkThey spread outThey boil

Which object would sink in water?

WoodIce cubePlastic bottleRock

What do thermoclines represent?

Layers by saltLayers by ageLayers by temperatureLayers by depth

Why is ice important in lakes?

It cools the waterIt adds saltIt insulates life belowIt breaks the surface

What is the main idea of the passage?

Why water freezesHow ships floatHow water density affects systemsWhat saltwater is made of

What happens to water's density with salt?

It dropsIt risesIt freezesIt evaporates

Perfect For:

👩‍🏫 Teachers

• Reading comprehension practice
• Auto-graded assessments
• Literacy skill development

👨‍👩‍👧‍👦 Parents

• Reading practice at home
• Comprehension improvement
• Educational reading time

🏠 Homeschoolers

• Reading curriculum support
• Independent reading practice
• Progress monitoring

Reading Features:

📖

Reading Passage

Engaging fiction or nonfiction text

❓

Comprehension Quiz

Auto-graded questions

📊

Instant Feedback

Immediate results and scoring

📄

Printable Version

Download for offline reading