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3 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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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