The Classification of Matter Chapter 15 The Classification of Matter

Section 1 Composition of Matter

Different Categories of Matter

Matter fits into 2 major categories… Pure Substances Mixtures Matter with a fixed composition Two types: Elements Compounds Matter without a fixed composition Two types: Heterogeneous mixtures Colloids Suspensions Homogeneous mixtures Solutions

Elements When all the atoms in a substance have the same identity Examples: Pencil lead is graphite, which is just carbon in solid form Oxygen tanks contain pure oxygen to help people with lung diseases breathe easier

Compounds When two or more elements are combined Examples: Water is a combination of hydrogen and oxygen (H2O) Air is a combination of multiple elements Salt is a combination of sodium and chloride (NaCl)

Homogeneous Mixtures Contain two or more substances blended evenly throughout The air we breathe, Kool Aid, and sweet tea are all homogeneous mixtures

Solutions Specific type of homogeneous mixture in which particles are so small they cannot be seen with a microscope and will never settle to the bottom of the container Vinegar and soft drinks are examples of solutions because they remain mixed thoroughly

Heterogeneous Mixtures Different materials can be easily distinguished Things like pizza, salad, chicken noodle soup, granite, and concrete are all heterogeneous mixtures

Colloids Particles are larger than those in solutions, but they are not heavy enough to settle to the bottom Paint, Jell-o, fog, and smoke are all examples of colloids

The Tyndall Effect To detect a colloid, shine a light through the substance If there is a definite beam of light visible, it is a colloid

Suspensions Heterogeneous mixtures in which particles will settle to the bottom because they are heavier Muddy water, oil and vinegar salad dressing, and snow globes are suspensions

Section 2 Physical & Chemical Properties Physical & Chemical Changes

Physical Properties Characteristics that can be observed without changing anything about the material Color Shape Size Density Melting point Boiling point Freezing point

Chemical Properties Indication of whether a material can undergo a chemical change Flammability Reaction to light Solubility Combustion Reactivity

Physical Change A change in size, shape, or state of matter The identity stays the same Ice cube melting Water boiling or freezing Color changes Cutting paper into smaller pieces Stretching a rubber band Grass growing

Chemical Change Change of one substance to another Eggs rotting Cars rusting Match burning Leaves decomposing Cooking anything Chemical reactions

Weathering Physical change: when rocks split after water seeps into cracks, freezes, then melts The pieces of rock that break off still have the same identity, they’re just smaller Chemical change: acid rain causes limestone to change its chemical makeup and dissolve The White Cliffs of Dover have been shaped by this process over time

Weathering Physical Chemical

The Law of Conservation of Mass The mass of all substances present before a chemical change is equal to the mass of all substances present after a chemical change Suppose logs in a fireplace had a mass of 85 kg After they burn, all you see is ashes. If you weigh the ashes, they may not have a mass of 85 kg. Where is the rest of the mass?