Chemistry Chapter One:
Classification of Matter
Matter is made up of very tiny units called atoms, of which we know about 114
types. Each type of atom is the building block of a different chemical element, thus
there are 114 elements. 90% of all elements are natural and the remaining
percentage of elements is those synthesized in the laboratories.
When two or more elements are joined, they form a compound. A compound is
made of many molecules. A molecule is the smallest entity having the same
proportions of the constituent atoms as does the compound as a whole.
An element and compounds are referred to as substances. When two or more
substances mix, they form a mixture. When a mixture is uniform in composition and
properties throughout, it is known as a homogeneous mixture or solution (e.g.
ordinary air, seawater, and gasoline). When the composition and physical properties
vary from one part of the mixture to another, it is known as a heterogeneous
mixture (e.g. sand and water).
Consider the mixture of sand and water being poured into a funnel lined with porous
filter paper. The water passes through, but the sand is retained. This process of
separation is known as filtration. On the other hand, we cannot filter a
homogeneous mixture of copper (II) sulphate. However, this compound can be
separated by boiling. This process is called distillation.
States of Matter
Matter generally exists in 3 states: solid, liquid, or gas. A solid contains atoms or
molecules in close contact, sometimes in a highly organized arrangement called a
crystal. As well, a solid had a definite shape. In a liquid, the atoms or molecules are
usually further apart. The movement of these atoms/molecules give a liquid its most
distinctive property: the ability to flow, covering the bottom and assume the
shape of its container. In a gas, the distance between atoms/ molecules is much
greater. A gas always expands to fill its container. ***In water, specifically ice, it is
important to remember that liquid water is more dense than ice, since all the
molecules in the liquid are joined tightly to each other to provide a sturdy
framework for a block of ice.***
SI and Non-SI Units (Read 1.4)
Density and Percent Composition
When someone says a ton of bricks weigh more than a ton of cotton, they have the
concepts of weight and density confused. Matter in a brick is more concentrated than in cotton, making bricks denser than cotton. Density is the ration of mass
to volume. Density (d) = mass (m)/ volume (v). Mass and volume are extensive
properties. An extensive property is dependent on the quantity of matter
observed, unless, the mass of the substance is divided by its volume. In this case,
that is an intensive property. This is an independent of the amount of matter
observed. (e.g. the density of water at 25ºC is the same whether it fills a small
beaker or a large pool.
Density is a function of temperature because volume varies with temperature,
whereas mass remains constant. For example, as the average temperature of
seawater increases, the seawater will become less dense and its volume will
increase. Another factor that affects density is state of matter. Generally, solids are
denser than liquids, and both are denser than gases.
Density in Conversion Pathways
1. A cube of osmium 1.000 cm on edge weighs 22.48g. The density of osmium,
therefore, is 22.48g/cm . What would be the mass of a cube of osmium that is