18.2 – Properties of Matter

Objectives Identify substances using physical properties. Contrast physical and chemical properties Compare and contrast physical and chemical changes. Identify chemical changes. Determine how the law of conservation of mass applies to chemical changes.

Properties Physical – characteristics that can be observed without altering identity of substance Density, color, melting point Chemical – characteristics that cannot be observed without altering identity of substance Flammability

Changes in matter Physical – alterations in form but not matter itself Does not alter identity Tear, Break, Grind, Dissolve, Freeze, Melt, Boil, Distill, Crush Chemical – does alter identity Produces different substance Burn, Cook, Rust, Decay, Digest

Distillation

Signs of Chemical Change Color Change Bubbles – gas produced Odor change Temperature change Precipitate forms – new solid made

Weathering Forces of nature are continuously shaping the Earth’s surface Rocks split Deep canyons are carved out Sand dunes shift Curious limestone formations decorate caves Physical & Chemical Change

Weathering - Physical Large rocks split as water seeps through small cracks Water freezes and expands Smaller pieces of newly exposed rock still have same properties of original rock

Weathering - Chemical Limestone, calcium carbonate, does not dissolve easily in water If water is slightly acidic because of the presence of carbon dioxide it reacts with limestone This change creates a new substance, calcium hydrogen carbonate, which dissolves in water

Weathering - Chemical Similar chemical change produces caves and icicle shaped rock formations

Law of Conservation of Mass Mass is neither created nor destroyed when chemical and physical changes occur Applies throughout universe and in all branches of science

Lavoisier Created with determining law of conservation of matter/mass First to recognize the role of oxygen in burning and rusting Guillotined during French Revolution

In-Class Assignment/Homework Learning Target Inventory Column 18.2 WKT