Book cover for Campbell Biology Concepts & Connections

Campbell Biology Concepts & Connections

Martha R. Taylor, Jean L. Dickey, Eric J. Simon, Kelly Hogan, Jane B. Reece

ISBN #9780134296012

9th Edition

631 Questions

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82,520 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This chapter provides a comprehensive overview of the chemical basis of life, emphasizing how elements combine to form compounds through various types of bonds such as covalent, ionic, and hydrogen bonds. It explores the fundamental structure of atoms, including the roles of isotopes, atomic numbers, and mass numbers, and highlights water’s unique properties that make it an indispensable solvent for life. Additionally, the chapter discusses the environmental repercussions of pH changes and shifts in ocean chemistry, particularly on organisms like corals, underscoring the intricate connection between chemistry and biology.

Learning Objectives

1

Explain the structure of atoms, including protons, neutrons, electrons, isotopes, atomic number, and mass number.

2

Describe how elements combine chemically to form compounds with emergent properties.

3

Differentiate between covalent, ionic, and hydrogen bonds and illustrate their roles in biological systems.

4

Analyze the unique properties of water and its significance as a solvent in supporting life.

5

Evaluate the impact of environmental factors, such as pH changes and ocean chemistry, on living organisms.

Key Concepts

CONCEPT

DEFINITION

Element

A pure substance consisting of only one type of atom, which cannot be broken down by chemical means.

Compound

A substance formed when two or more elements chemically combine in fixed proportions, often with emergent properties.

Atom

The basic unit of matter composed of protons, neutrons, and electrons.

Isotope

Variants of a given element’s atoms that differ in the number of neutrons in the nucleus.

Atomic Number

The number of protons in the nucleus of an atom, defining the identity of the element.

Mass Number

The total number of protons and neutrons in an atom’s nucleus.

Covalent Bond

A chemical bond formed by the sharing of electron pairs between atoms.

Ionic Bond

A chemical bond formed by the electrostatic attraction between oppositely charged ions.

Hydrogen Bond

A weak bond that occurs when a hydrogen atom, already covalently bonded to a highly electronegative atom, experiences attraction to another electronegative atom.

pH

A measure of the acidity or basicity of a solution, which impacts chemical reactions and biological systems.

Solvent Properties of Water

Unique characteristics of water, including its polarity and hydrogen bonding, which allow it to dissolve many substances and moderate temperature.

Example Problems

Example 1

Fill in the blanks in this concept map to help you tie together the key concepts concerning elements, atoms, and molecules. (GRAPH CANNOT COPY)

Example 2

Create a concept map to organize your understanding of the life-supporting properties of water. A sample map is in the answer section, but the value of this exercise is in the thinking and integrating you must do to create your own map.

Example 3

Changing the _________ would change it into an atom of a different element. a. number of electrons surrounding the nucleus of an atom b. number of protons in the nucleus of an atom c. electrical charge of an atom d. number of neutrons in the nucleus of an atom

Example 4

What is chemically nonsensical about this structure? $$\mathrm{H}-\mathrm{C}=\mathrm{C}-\mathrm{H}$$

Example 5

A solution at pH 6 contains _________ H+ than the same amount of a solution at pH 8. a. 20 times more b. 100 times more c. 2 times less d. 100 times less
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Step-by-Step Explanations

QUESTION

How do you determine the mass number of an atom if it has 6 protons and 6 neutrons?

STEP-BY-STEP ANSWER:

Step 1: Identify the number of protons: In this case, 6.
Step 2: Identify the number of neutrons: In this case, 6.
Step 3: Add the number of protons and neutrons together to find the mass number.
Step 4: Calculation: 6 (protons) + 6 (neutrons) = 12.
Final Answer: The mass number of the atom is 12.

Atomic Structure

QUESTION

Explain the process involved in forming a covalent bond between two atoms.

STEP-BY-STEP ANSWER:

Step 1: Recognize that each atom has electrons in its outer shell that can be shared.
Step 2: Identify that when two atoms approach each other, they may share one or more pairs of electrons to achieve a more stable, lower-energy configuration.
Step 3: Understand that the shared electrons count toward the outer electron count of both atoms, helping each achieve a full valence shell.
Step 4: Conclude that this sharing results in a covalent bond, linking the atoms into a molecule.
Final Answer: A covalent bond forms when two atoms share electron pairs to achieve full outer electron shells and increased stability.

Covalent Bond Formation

QUESTION

How do hydrogen bonds contribute to the cohesive and temperature-moderating properties of water?

STEP-BY-STEP ANSWER:

Step 1: Recognize that water molecules are polar, with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms.
Step 2: Understand that the positive part of one water molecule is attracted to the negative part of another, creating hydrogen bonds.
Step 3: Note that these bonds are relatively weak compared to covalent bonds, yet they occur in large numbers.
Step 4: Explain that the network of hydrogen bonds gives water high cohesion, leading to its high surface tension, and absorbs significant energy before breaking, which moderates temperature changes.
Final Answer: Hydrogen bonds in water create a cohesive network that supports large surface tension and high heat capacity, enabling water to moderate temperature effectively.

Water’s Hydrogen Bonds

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Common Mistakes

  • Confusing the nature of different chemical bonds, such as mixing up ionic and covalent bonding mechanisms.
  • Overlooking the significance of hydrogen bonds in determining water’s unique properties.
  • Misunderstanding the difference between atomic number and mass number.
  • Assuming that all compounds have emergent properties without considering specific bond interactions.
  • Underestimating the impact of pH changes on biological systems and environmental processes.