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Overview
Learn about the composition of matter Learn the difference between elements
and compounds Distinguish between physical and
chemical properties and changes Distinguish between mixtures and pure
substances Learn 2 methods of separating mixtures
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Did you ever wonder?... How do plants grow & why are they green? Why is the sun hot? Why does a hot dog get hot in a microwave? Why does wood burn and rocks do not? How does soap work? Why does pop fizz? What’s happening when iron rusts? Why doesn’t aluminum foil rust? How does a hair permanent work?
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The Particulate Nature of Matter Matter: the “stuff” the universe is
composed ofHas mass and occupies spaceComes in many forms: the stars, your chair,
brain tissue Composed of tiny particles called atoms
Scanning tunneling microscope produces images of atoms
Can’t see with naked eye, similar to looking at beach from far away; can only see sand particles when you get close
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Elements and Compounds Atoms: all matter is composed of these tiny
particlesOver 100 different atomsSimilar to words, all made from 26 different lettersAll matter made from about 100 different atoms
Compounds: substances made by bonding atoms together in specific waysContain 2 or more different types of atomsSame throughout
Molecule: made up of atoms that are “stuck” together
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Elements Some atoms can combine with
like atoms to form molecules: H2 & O2
Carbon bonds forming large groups
Elements: substances that contain only one type of atom
Compound: always contains atoms of different elements (water = H2O)
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Figure 2.7: The three states of water: Liquid
Liquid: has a definite volume but takes the shape of its container
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Figure 2.7: The three states of water: Gas.
Gas: has no fixed volume or shape; uniformly fills any container
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Physical and Chemical Properties and Changes
Physical Properties: Odor, color, volume, state, density, melting point, and boiling point
Chemical properties: refer to a substances ability to form new substancesExamples: wood burning, rusting of steel,
digestion of food, growth of grassGiven substance changes to a fundamentally
different substance or substances
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Chemical vs. Physical change in water
Physical changes solid → liquid → gas
Change of state: H2O molecules still present
Chemical change = electrolysiswater changed into different substances (water
decomposes to hydrogen & oxygen)
Physical & Chemical Changes
Physical change involves a change in one or more physical properties, but no change in fundamental components of substance. Most common are changes in state.
Chemical change involves a change in the fundamental components of the substance. Chemical changes are called reactions.
Mixtures and Pure Substances
Mixture: something that has variable compositionExamples: soda, coffee, tap water, air
Composition of mixtures varies, but composition of compounds is always the same
Composition depends on how much of each component is used when mixture is formed
Can be separated into pure substances: elements and/or compounds
Mixtures: Alloys
Alloys: mixtures of metalsMany gold alloys: mixture of gold, copper, and
silverThey are not compounds! (like water)Composition varies
Figure 2.10: Twenty-four-karat gold is an element Eighteen-karat gold is an alloy. Fourteen-karat gold is an alloy.
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Homogeneous and Heterogeneous
Homogeneous mixture is the same throughout, & also called a solutionExamples: salt water, air, brass (mixture of
copper and zinc)
Heterogeneous mixture contains regions that have different properties from other regions Examples: sand/water mixture, rocky road ice
cream, chocolate chip cookie dough
Distillation: Separation Process
Boil water (or other liquid) Vaporizes (turns into gas = steam) Condense (cool steam in tube) – turns
back to liquid Minerals are left behind Pure water collected Physical change
Filtration: Separation Process
Pour mixture onto a mesh, such as filter paper
Liquid passes through, solid is left behind on filter paper
Pure Substances
Pure substances are either elements or compounds
Always have same chemical and physical properties