Introductory Chemistry: A Foundation - Zumdahl S.S., DeCoste D.J. 2019

Matter

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Colorful morning landscape of ice floating in Jokulsarion, Iceland.

As you look around you, you must wonder about the properties of matter. How do plants grow, and why are they green? Why is the sun hot? Why does a hot dog get hot in a microwave oven? Why does wood burn, whereas rocks do not? What is a flame? How does soap work? Why does soda fizz when you open the bottle? When iron rusts, what’s happening? And why doesn’t aluminum rust? How does a cold pack for an athletic injury, which is stored for weeks or months at room temperature, suddenly get cold when you need it? How does a hair permanent work?

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Why does soda fizz when you open the bottle?

The answers to these and endless other questions lie in the domain of chemistry. In this chapter we begin to explore the nature of matter: how it is organized and how and why it changes.

Objective

· To learn about matter and its three states.

Matter , the “stuff” of which the universe is composed, has two characteristics: it has mass, and it occupies space. Matter comes in a great variety of forms: the stars, the air that you are breathing, the gasoline that you put in your car, the chair on which you are sitting, the turkey in the sandwich you may have had for lunch, the tissues in your brain that enable you to read and comprehend this sentence, and so on.

To try to understand the nature of matter, we classify it in various ways. For example, wood, bone, and steel share certain characteristics. These things are all rigid; they have definite shapes that are difficult to change. On the other hand, water and gasoline, for example, take the shape of any container into which they are poured (Fig. 3.1). Even so, L of water has a volume of L whether it is in a pail or a beaker. In contrast, air takes the shape of its container and fills any container uniformly.

Figure 3.1.

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Liquid water takes the shape of its container.

The substances we have just described illustrate the three states of matter : solid , liquid , and gas . These are defined and illustrated in Table 3.1. The state of a given sample of matter depends on the strength of the forces among the particles contained in the matter; the stronger these forces, the more rigid the matter. We will discuss this in more detail in the next section.

Table 3.1. The Three States of Matter