Matter. Overview Learn about the composition of matter Learn the difference between elements and compounds Distinguish between physical and chemical.

Matter

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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Atom Combinations

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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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Top Ten

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Figure 2.5: The three forms of the element carbon: Diamond.

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Figure 2.5: The three forms of the element carbon: Graphite.

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Figure 2.5: The three forms of the element carbon: Buckminsterfullerene.

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The States of Matter

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Figure 2.7: The three states of water: Solid.

Solids: Rigid; have a fixed shape and volume

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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)

Electrolysis, the decomposition of water by an electric current, is a chemical process.

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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

The composition of air.

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Chart examining each substance of air.

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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

Representation of H2O molecules.

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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

The solution is boiled and steam is driven off.

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Salt remains after all water is boiled off.

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No chemical change occurs when salt water is distilled.

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Filtration: Separation Process

Pour mixture onto a mesh, such as filter paper

Liquid passes through, solid is left behind on filter paper

Filtration separates a liquid from a solid.

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Separation of a sand-saltwater mixture.

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Pure Substances

Pure substances are either elements or compounds

Always have same chemical and physical properties

The organization of matter.

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Setup to boil water.

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