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Covalent Bonds — Reading Comprehension

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This comprehensive middle school science passage, designed for grades 6-8 and aligned with NGSS standard MS-PS1-1, introduces students to the concept of covalent bonds. Students will learn how atoms share electrons to form molecules, contrasting this process with ionic bonding. The passage provides clear explanations, real-world examples such as water (H₂O) and carbon dioxide (CO₂), and simple Lewis dot diagrams to illustrate electron sharing. Interactive features include a glossary of science terms, a multiple-choice quiz, writing prompts, and graphic organizers to deepen understanding. The content is scaffolded with a differentiated reading version and Spanish translations, making it accessible to a broad range of learners. With integrated audio support and engaging, standards-based activities, this resource supports inquiry-based learning and helps students build foundational chemistry skills for future science success.

CONTENT PREVIEW

Covalent-bonds-2 — Diagram of electron sharing in covalent bonds

Covalent bonds are essential to life and matter on Earth. For example, water can dissolve many substances and carbon dioxide is crucial for plants to make food. Both water and carbon dioxide are created when atoms join together by sharing electrons, not by taking or giving them away. Understanding how atoms share electrons helps explain why molecules have the properties they do, and why some substances behave differently from others.

How Covalent Bonds Work

Atoms are made of a nucleus surrounded by electrons. When two nonmetal atoms want to fill their outer electron shells, they can share one or more pairs of electrons. This sharing creates a covalent bond, forming a molecule. For example, in a water molecule (H₂O), each hydrogen atom shares one electron with oxygen, and oxygen shares one electron with each hydrogen. This creates two single covalent bonds. A double covalent bond, like in carbon dioxide (CO₂), involves two pairs of shared electrons between carbon and each oxygen atom. Sometimes, atoms share three pairs of electrons, forming a triple bond, as seen in nitrogen gas (N₂). Lewis dot structures use dots to show these shared electrons, making it easier to see how atoms are connected.

Covalent vs. Ionic Compounds

Covalent bonds are different from ionic bonds. In ionic bonding, atoms transfer electrons, creating positive and negative ions that stick together. Table salt (NaCl) is an example of an ionic compound. In covalent compounds, like water or oxygen gas (O₂), there are no charged ions. Instead, atoms form stable molecules by sharing electrons. Molecules made from covalent bonds tend to have lower melting points and may not conduct electricity, unlike many ionic compounds. These differences are crucial in chemistry and daily life, affecting everything from how water dissolves salt to how plastics are made.

Applications and Broader Connections

Many substances important to life are made of covalent molecules. For example, DNA, proteins, and sugars all have covalent bonds. Chemists use the idea of electron sharing to design new medicines and materials. The study of covalent bonding also helps us understand chemical reactions, climate change (because of carbon dioxide), and even how our bodies use oxygen. Understanding covalent bonds connects to larger principles, such as the conservation of matter and how energy is stored in chemical bonds.

Covalent bonds are a foundation of chemistry, explaining how atoms stick together to form the world around us. From the air we breathe to the food we eat, covalent molecules shape our lives and our planet. As science advances, new discoveries about how atoms bond may lead to new technologies and solutions for global challenges.

Interesting Fact: The oxygen we breathe (O₂) is held together by a double covalent bond, making it stable and essential for life!

What is the main way atoms form covalent bonds?

By sharing electronsBy giving away electronsBy taking electrons from other atomsBy becoming ions

Which of the following is an example of a molecule formed by covalent bonds?

H₂O (water)NaCl (table salt)Fe (iron)MgO (magnesium oxide)

What does a double covalent bond mean?

Two pairs of electrons are sharedOne electron is transferredAtoms repel each otherThree pairs of electrons are shared

In the passage, the term 'molecule' refers to what?

A group of atoms held together by covalent bondsAn atom by itselfA group of ionsA metal crystal

What is shown in a Lewis dot structure?

Shared electrons between atomsElement namesPhysical appearance of moleculesThe color of the atoms

How are ionic bonds different from covalent bonds?

Ionic bonds involve electron transfer; covalent bonds involve electron sharingIonic bonds only form in waterCovalent bonds make ionsIonic bonds use Lewis dot structures

Which statement best describes a triple covalent bond?

Three pairs of electrons are shared between two atomsIt only happens in metalsAtoms lose three electronsIt is weaker than a single bond

Why do molecules with covalent bonds tend to have lower melting points?

Because there are no strong attractions like in ionic compoundsBecause they are heavierBecause they conduct electricityBecause they are made of metals

True or False: Covalent bonds always form between metals and nonmetals.

FalseTrue

True or False: DNA, proteins, and sugars all have covalent bonds.

TrueFalse