Chemistry 101

Chapter 1Goals, Method & Measurements

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Definition of Chemistry

Chemistry , is the study of that part of nature that bears on substances, their compositions and structures, and their abilities to be changed into other substances.

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Facts

Fact - a truth known by actual experience or observation. The hardness of iron, the number of ribs in a squirrel’s bodies, the existence of fossil trilobites, and the like are all facts. In science, the most reliable facts are those that can be obtained through repeated observations or measurements.

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Hypothesis

Hypothesis - a proposition explaining the occurrence of a phenomenon or phenomena, often asserted as a conjecture to guide further investigation.

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Theory

Theory - a coherent set of propositions that explain a class of phenomena, that are supported by extensive factual evidence, and that may be used for prediction of future observations.

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Famous Theories

Scientists have produced lots of familiar theories:

Copernicus's theory of the heliocentric solar system

Newton's theory of gravity

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Famous Theories

Einstein's theory of relativity, Darwin's theory of natural selection

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Facts & Theories

Each of these theories draws on huge numbers of facts:

observations of the passage of the sun and planets for the heliocentric theory;

the behavior of the planets, of projectiles, and rather famously of apples for the theory of gravity,

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Facts & Theories

the existence and location of fossils, as well as the modern distribution and reproduction of organisms, for the theory of natural selection

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Properties & States of Matter

A property is any characteristic of something that can be used to identification and recognition.

Physical properties include color, height, mass, and they can be observed without the object being changed.

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Properties & States of Matter

a chemical that when observed, causes a substance to change into new substances is called a chemical property and the observation, is called a chemical reaction.

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Properties & States of Matter

Physical Change Boiling Water Dissolving salt in

water Evaporation of water Cooking an egg

Chemical Change Rusting of iron Burning of wood Cooking an egg.

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Physical Quantities & Measurements

Length – a physical quantity that describes how far an object extends into space.

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Some Common Measures of Length

SI (International System of Units)1 Kilometer = 1000 meters1 meter = 100 centimetersI centimeter = 10 millimeter

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Some Common Measures of Length

U.S. Customary1 mile + 5280 feet1760 yard1 yard = 3 feetI foot = 12 inches

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Volume

The space an object occupiesSome Common Measures of LengthSI1 Cubic meter = 1000 liters1 liter = 1000 milliliters1 milliliter = 1000 micro liters

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Volume

U.S. Customary1 gallon = 4 liquid quarts1 liquid quarts = 2 liquid pints1 liquid pint = 16 liquid ounces

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Mass

Mass – the measure of the inertia of an object.

An object with a large inertia has a large mass. A large mass doesn’t always mean a large weight. This is because, mass is not dependent on location, whereas weight is.

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Mass

Some common measures of MassSI1 kilogram = 1000 grams1 gram = 1000 milligrams1 milligram = 1000 micrograms1 kilogram = 2.205ibs

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Mass

U.S. Customary (avoirdupois)c

1Short ton = 2000 pounds1 pound = 16 ounces1 pound = 453.6 grams

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Temperature

Temperature – is the base quantity used to describe the hotness and coldness of an object.

Temperature can be expressed in : Celsius / Centigrade Kelvin Fahrenheit

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Significant Figures

The number of significant figures in a physical quantity is the number of digits known with complete certainty to be accurate plus one

1.03 x 104 g                (three significant figures)

1.030 x 104 g              (four significant figures) 1.0300 x 104 g            (five significant figures)

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Density & Specific Gravity

Density is the mass per unit volume of a substance (mass \ volume)

The density of substance varies with temperature, because for most substances, the mass of the substance changes with temperature, not its volume.

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Density & Specific Gravity

Substance Density (g/cm3)

Aluminum 2.70 Bone 1.7 – 2.0 Glass 2.4 – 2.8 Gold 19.3

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Density & Specific Gravity

The specific gravity of a liquid is the ratio of the mass contained in a given volume to the mass in the same unit of the identical volume of water at the same temperature.

Specific gravity is measured without units.

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The End