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Mixtures and Pure Substances — Reading Comprehension

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MS-PS1-1

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This middle school science passage provides an in-depth exploration of mixtures and pure substances, directly aligned to NGSS standard MS-PS1-1. Students will learn to distinguish between elements, compounds, and mixtures, understanding why and how their properties differ. The passage explains scientific mechanisms, such as why pure substances have fixed compositions, while mixtures retain the individual properties of their components. Real-world examples, including salt, trail mix, distilled water, and ocean water, make concepts relatable. The resource includes a glossary, Spanish translation, a simplified version for accessibility, comprehension and vocabulary quizzes, writing activities, and graphic organizers for structured learning. Audio integration ensures accessibility for all learners. This resource supports scientific literacy and helps students apply knowledge to environmental, health, and technological questions.

CONTENT PREVIEW

homogeneous-mixture-1 — A mixture is made when two or more substances are combined.

Matter makes up everything in our world, from water in a river to the air we breathe. Scientists classify matter into two main categories: pure substances and mixtures. Understanding the differences between these categories is essential for studying chemistry and solving real-world problems, such as cleaning polluted water or designing new materials.

What Are Pure Substances?

Pure substances are materials made up of only one type of particle. These particles can be either elements or compounds. Elements, like oxygen or gold, contain only one kind of atom. Compounds are made of two or more elements bonded together in fixed ratios, such as water (H₂O) or table salt (NaCl). A key feature of pure substances is their consistent properties; for example, pure salt always tastes the same and melts at a specific temperature. This happens because the particles are always arranged in the same way.

How Mixtures Differ from Pure Substances

A mixture is made when two or more substances are combined, but not chemically bonded. Each component in a mixture retains its own properties. For instance, trail mix contains nuts, raisins, and chocolate chips. You can see and separate each part, and each piece still tastes like itself. Mixtures can be homogeneous (evenly mixed, like saltwater) or heterogeneous (unevenly mixed, like salad). Unlike pure substances, mixtures do not have a fixed composition. The amount of each part can vary; for example, ocean water contains different amounts of salt, minerals, and water, depending on location.

Interactions, Applications, and Scientific Importance

The separation of mixtures uses the distinct properties of their components. For example, salt can be separated from ocean water by evaporation, leaving pure salt crystals behind. Distilled water is a pure substance made by boiling water and condensing the steam, removing dissolved minerals. Understanding the difference between mixtures and pure substances is crucial for many scientific and industrial processes, such as producing medicines or ensuring safe drinking water. This classification also helps scientists predict how materials will behave in different situations, like how pollutants move in the environment.

Mixtures and pure substances are part of a larger system of chemical classification. Their study is connected to the conservation of mass and the behavior of particles, which are fundamental ideas in physical science. By analyzing the properties and interactions of these materials, scientists can design new products, develop environmental solutions, and understand natural processes at a deeper level.

Interesting Fact: Nearly all natural water sources, including rain, rivers, and oceans, are mixtures, not pure substances!

What is a pure substance?

A material made of only one kind of particleA mixture of two or more substancesA substance that changes its propertiesA combination of liquids and solids

Which of the following is an example of a mixture?

Distilled waterTable saltTrail mixOxygen gas

Why do pure substances always have the same properties?

Because they contain only one type of particle arranged in the same wayBecause they are mixed evenlyBecause their amount changes every timeBecause they are always liquids

What is the main difference between a compound and a mixture?

Compounds are made of one kind of atom, mixtures are notCompounds are chemically bonded, mixtures are notMixtures have fixed ratios of elementsCompounds are always solids

What does 'homogeneous' mean in the context of mixtures?

The parts are mixed unevenlyThe mixture looks the same throughoutIt is made of only one elementIt cannot be separated

What does 'conservation of mass' mean?

Mass is created during chemical changesMass is destroyed when substances mixMass is not created or destroyed in physical and chemical changesMass only exists in mixtures

If you separate salt from ocean water by evaporation, what kind of process is this?

Separating a compound into elementsSeparating a mixture using physical propertiesCreating a new elementMaking a homogeneous mixture

Which is TRUE about mixtures?

The parts are chemically bonded togetherThey always have the same amount of each partEach part keeps its own propertiesThey are always liquids

Ocean water is a pure substance. True or False?

TrueFalse

Elements and compounds are both types of pure substances. True or False?

TrueFalse