Understanding General Chemistry

Atef Korchef

• Publisher: CRC Press
• Year: 2022
• ISBN:
  9781000542226
• Edition: 1
• Topic: Ciencias biológicas
• Subtopic: Ciencias en general

Understanding General Chemistry details the fundamentals of general chemistry through a wide range of topics, relating the structure of atoms and molecules to the properties of matter. Written in an easy-to-understand format with helpful pedagogy to fuel learning, the book features main objectives at the beginning of each chapter, get smart sections, and check your reading section at the end of each chapter. The text is filled with examples and practices that illustrate the concepts at hand. In addition, a summary, and extensive MCQs, exercises and problems with the corresponding answers and explanations are readily available.

Additional features include:

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• Alerts students to common mistakes and explains in simple ways and clear applications how to avoid these mistakes.

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• Offers answers and comments alongside sample problems enabling students to self-evaluate their skill level.

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• Includes powerful methods, easy steps, simple and accurate interpretations, and engaging applications to help students understand complex principles.

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• Provides a bridge to more complex topics such as solid-state chemistry, organometallic chemistry, chemistry of main group elements, inorganic chemistry, and physical chemistry.

This introductory textbook is ideal for chemistry courses for non-science majors as well as health sciences and preparatory engineering students.

1 Matter

DOI: 10.1201/9781003257059-1

1.1 Objectives

At the end of this chapter, the student will be able to:

1. Define the states of matter and compare their properties.
2. Differentiate between the types of matter (elements, compounds, mixtures).
3. Differentiate between chemical properties and physical properties.
4. Differentiate between chemical change and physical change.

1.2 Chemistry and Matter

Chemistry is the study of matter and the changes that matter undergoes. Matter is defined as anything that has mass, occupies space and is made up of particles.

1.3 States of Matter

The states of matter differ from each other in terms of the distance and the attractive forces between their constituent particles.

Solids exhibit high attractive forces and very short distances between particles. As a result, the particles are close together and show little freedom of motion. A solid has a fixed volume and shape, and changes very little as temperature and pressure change slightly.

However, the attractive forces in gases are significantly lower than in solids and the distance between the particles is markedly greater. In a gas, the particles are randomly spread apart and have complete freedom of movement. A gas sample conforms to both the shape and volume of the container it fills. The volume of a gas varies considerably in response to either temperature or pressure.

The attractive forces in liquids are greater than those in gases but lower than those in solids. In a liquid, the particles are close together but not held rigidly in position; these particles are free to move past one another. A liquid sample has a fixed volume but assumes the shape of the container it fills.

1.4 Types of Matter

Matter is classified as either a substance or a mixture of substances.

1.4.1 Substances

A substance can be either an element or a compound and has a definite composition and distinct properties.

An element cannot be separated into simpler substances by chemical means. All the elements are cited in the periodic table of elements. The chemical symbol of an element is represented by one capital (uppercase) letter, or a capital letter followed by a small (lowercase) one.

• Examples: hydrogen (H), carbon (C), nitrogen (N), oxygen (O), sulfur (S), iron (Fe), mercury (Hg), chlorine (Cl) and calcium (Ca).

Note that the building up unit (i.e., the smallest unit) of an element that has all the properties of the element is the atom.

A compound consists of two or more different elements that are chemically combined in definite ratios. The properties of the compounds are different from the properties of their elements.

• Examples: NaCl, H₂O, CO₂, CaCO_3, Fe(NO₃)₂, Mg₃(PO₄)₂, MgC1₄H₁₀O₄ and CaSO₄·2H₂O are formed of different elements, so all of these are compounds.

Get Smart

A molecule or a compound?

When two or more atoms of the same or different elements are chemically combined, they form a molecule. A molecule formed by atoms from different elements, such as NaCl and H₂O, is the building up unit (i.e., the smallest part) of a compound that still has all the properties of that compound. On the other hand, a molecule formed of two or more atoms of the same element, such as H₂, O₂ or O₃, cannot be the smallest part of a compound since a compound consists of two or more different elements that are chemically combined in definite ratios.

1.4.2 Mixtures

A mixture is a physical combination of two or more substances (elements or compounds). Substances retain distinct identities. A mixture can be either homogeneous or heterogeneous.

A homogeneous mixture is one in which the components are uniformly distributed. The composition of the mixture is uniform throughout

• Examples: air, seawater, alloys, sugar dissolved in water, chemical solutions (e.g., aqueous solutions of NaCl, NaOH, H₃PO₄ or KMNO₄, etc.).

A solution is a homogenous mixture of two or more substances which are chemically unreactive. A solution is composed of the solute and the solvent. The solute is the substance present in the smaller amount and the solvent is the substance present in the larger amount. When a liquid and a solid form a solution, the liquid is the solvent whatever the amounts of the substances in the mixture. Water is considered to be the most common inorganic solvent, while benzene is the most common organic solvent. All solutions are homogeneous mixtures.

Solubility is the property of a solute (solid, liquid, or gaseous chemical substance) to disso...