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Chapter 1

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Alison Blay- Palmer

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). Separating Mixtures 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 1.25 in
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