Chemistry Chapter 2 Study Guide

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Questions and Answers

What does it mean that water is a polar molecule, and why is this important?

Water is a non-polar molecule that cannot dissolve anything.

Water has an unequal charge, allowing it to dissolve other polar molecules. (correct)

Water has a balanced charge, making it ineffective as a solvent.

Water is mostly positive and cannot bond with anything.

What is a polar covalent bond?

The unequal sharing of electrons.

What is a non-polar covalent bond?

The equal sharing of electrons.

What is an ionic bond? Give an example.

The transfer of electrons; an example is Na transferring an electron to Cl to form NaCl. Signup and view all the answers

What is an ion?

An atom with a charge. Signup and view all the answers

Why are polar covalent bonds and non-polar covalent bonds important?

They determine the properties of water, such as solvent ability and cohesion. Signup and view all the answers

What is the difference between a molecule, element, and compound?

A molecule is two or more atoms held together by covalent bonds, an element is a substance that cannot be broken down further, and a compound is two or more elements in a fixed ratio. Signup and view all the answers

Describe the relationship between hydrogen bonds, oxygen as an electron hog, and polar covalent bonds.

Oxygen attracts hydrogen molecules, creating polar covalent bonds and hydrogen bonds. Signup and view all the answers

What is an ionic bond?

The transfer of electrons. Signup and view all the answers

What is a hydrogen bond?

The interaction between a charged hydrogen atom on one water molecule and an oppositely charged atom (oxygen) on another. Signup and view all the answers

What is an acid?

A substance that has a higher concentration of hydrogen ions than hydroxide ions. Signup and view all the answers

What is a base?

A substance that has a higher concentration of hydroxide ions and lower concentration of hydrogen ions. Signup and view all the answers

What does the pH scale measure?

How acidic or basic a substance is. Signup and view all the answers

If water has a pH of 7, what do we know about this molecule?

It is a whole water molecule, not one that has broken apart. Signup and view all the answers

Why is water considered the universal solvent?

Because it is a polar molecule, allowing it to break up ionic bonds and dissolve substances. Signup and view all the answers

Match the following properties of water:

Cohesion = The ability of water to hydrogen bond to other water molecules. Adhesion = The clinging of water to another substance. Surface Tension = A measure of how difficult it is to stretch or break the surface of water. Capillary Action = The movement of water within the spaces of a porous material. Signup and view all the answers

What is cohesion?

The ability of water to hydrogen bond to other water molecules. Signup and view all the answers

What is adhesion?

The clinging of water to another substance. Signup and view all the answers

What is surface tension?

A measure of how difficult it is to stretch or break the surface of water. Signup and view all the answers

What is capillary action?

The movement of water within the spaces of a porous material due to adhesion, cohesion, and surface tension. Signup and view all the answers

What is the significance of CHNOPS?

It represents carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur, which are the most abundant elements in living organisms. Signup and view all the answers

Study Notes

Water as a Polar Molecule

Water exhibits polar characteristics due to unequal charge distribution, with partial positive and negative regions.
This polarity enables water to dissolve other polar substances easily, such as salts and sugars.

Polar and Non-polar Covalent Bonds

Polar covalent bonds involve the unequal sharing of electrons.
Non-polar covalent bonds entail equal sharing of electrons.

Ionic Bonds

Ionic bonds are formed through the transfer of electrons, e.g., sodium (Na) transfers an electron to chlorine (Cl), resulting in NaCl (table salt).

Definition of Ions

An ion is defined as an atom with a net electric charge due to the loss or gain of one or more electrons.

Importance of Covalent Bonds

Polar and non-polar covalent bonds dictate many properties of water, such as its solvent capabilities, cohesion, and surface tension.
Only polar covalent bonds can form hydrogen bonds, attracting hydrophilic (water-loving) substances while repelling hydrophobic (water-repelling) substances.

Molecules, Elements, and Compounds

A molecule consists of two or more atoms linked by covalent bonds.
An element cannot be decomposed into simpler substances, and a compound consists of two or more different elements bonded in a fixed ratio (e.g., NaCl).

Relationship of Hydrogen Bonds and Electronegativity

Oxygen's high electronegativity results in an unequal sharing of electrons, leading to polar covalent bonds.
This polarity enables the formation of hydrogen bonds between water molecules, where the positively charged hydrogen of one molecule attracts the negatively charged oxygen of another.

Acids and Bases

An acid has a higher concentration of hydrogen ions (H+) than hydroxide ions (OH-), e.g., vinegar.
A base has a higher concentration of hydroxide ions and a lower concentration of hydrogen ions, e.g., bleach.

pH Scale

The pH scale quantifies the acidity or basicity of substances, with water being neutral at a pH of 7.

Universal Solvent

Water is termed the universal solvent due to its polar nature, which allows it to disrupt ionic bonds and dissolve a variety of substances.

Properties of Water

Key properties of water include cohesion, adhesion, surface tension, and capillary action.

Cohesion

Cohesion refers to water's ability to bond with itself through hydrogen bonding, crucial for processes like nutrient transport in trees.

Adhesion

Adhesion is the attraction between water and other substances, demonstrated when water makes glass slides stick together.

Surface Tension

Surface tension measures the difficulty of breaking the water surface, enhanced by hydrogen bonding, allowing insects to walk on water.

Capillary Action

Capillary action describes the movement of water through a porous material due to cohesion, adhesion, and surface tension, facilitating nutrient transport in plants.

CHNOPS Significance

CHNOPS stands for carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur, highlighting the primary elements essential to life forms.

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Description

This quiz focuses on key concepts from Chemistry Chapter 2, particularly the properties of water as a polar molecule. Understanding these properties is essential for grasping how water interacts with other substances, including its ability to dissolve various compounds. Test your knowledge and reinforce your understanding of these foundational concepts.