CHEM 392D1 Lecture Notes - Chemical Element, Osmium, Decimal Mark
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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