The Language of Chemistry

Earlier there were several references to terms like quantitative and chemical reaction. These terms along with many others form the basis of the language of chemistry. In order to communicate what needs to be understood in this course, you will need to be familiar with these terms. Or in other words, learn to speak chemistry.

Let's start with defining chemistry in general. Chemistry is the study of the composition, properties and behavior of matter. And as we define the word we also add to our list of needed definitions – What is matter? What is meant by the terms composition, properties and what behaviors might a chemical compound have?

Matter is anything that has mass and volume i.e. takes up space. This pretty much means that chemistry is the study of just about everything. We define matter by its composition – what it is made of chemically. All matter is composed of elements. The periodic table shows that there are 118 known elements.

The Periodic Table

States & Properties of Matter

As we look further at our definition of matter, we find many more terms used in common chemistry language. Matter is made up of various materials and can be observed in many states.

The states of matter are defined as solid, liquid or gas. Each of these states has its own properties. Solids have a defined shape and volume. Liquids have a defined volume but assume the shape of the container they are placed in and gases have neither a defined shape nor volume. They will expand to the limits of whatever container they are in.

Matter is also defined by its composition. The terms heterogeneous and homogeneous refer to the uniformity of the composition of the matter under study. A heterogeneous mixture is one in which the individual components of the mixture are discernible. In a homogeneous mixture the components are uniformly distributed and cannot be discerned one from another.

Examples of heterogeneous mixtures include oil and water, a pizza and most soups. Examples of homogeneous mixtures would include blood or air. Homogeneous can also refer to pure substances rather than just mixtures. These substances are composed of either compounds which consist of two or more elements; or just an element alone. And all elements, compounds and therefore all substances are composed of atoms.

The properties of matter are also defined as either chemical or physical. A Chemical property can only be determined by reaction. This means that the property is only in evidence when the substance undergoes a change in chemical composition. Chemical properties can also be thought of in terms of the behavior of a substance. Whether a chemical will react or not defines its behavior. Properties such as flammability or toxicity are chemical in nature.

Properties of Matter - Physical and Chemical Properties
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Physical properties are those that require no reaction to be observed. Color, mass, density, melting point, freezing point and many others are considered physical properties of a substance. Physical properties are further defined as being either intensive or extensive. Extensive properties are those that are not dependent on the amount of the substance present. These properties include things like color, melting and freezing points or density. The Intensive properties are those that do depend on the amount of substance present. These properties would include mass, volume and length.