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Chapter 15

Chapter 15. Classification of Matter. Sec. 1 Composition of Matter. All materials are either made of pure substances or mixtures. Substance —an element or compound, definite composition Element —a substance with atoms that are all alike Ex. Carbon (C) & Magnesium (Mg)

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Chapter 15

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  1. Chapter 15 Classification of Matter

  2. Sec. 1 Composition of Matter • All materials are either made of pure substances or mixtures. • Substance—an element or compound, definite composition • Element—a substance with atoms that are all alike • Ex. Carbon (C) & Magnesium (Mg) • You can find them on the periodic table!! • Compound—a substance that contains 2 or more elements combined chemically. • Ex. Table salt (NaCl) & Hydrogen peroxide (H2O2)

  3. Mixtures • Mixture—a material made of 2 or more substances that can be separated physically. • There are 2 types of mixtures: heterogeneous and homogeneous. • Heterogeneous Mixture—different materials can be distinguished easily. • Ex. Pizza, salad, chocolate chip cookies (mmm) • Homogeneous Mixture—substances are blended evenly throughout. • Ex. Pop, vinegar • A homogeneous mixture is also called a solution.

  4. Colloids & Suspensions • Colloid—a type of mixture that never settles. • Ex. Paint & fog • A colloid is not the same as a solution • Colloids often appear foggy • If you shine a light on a colloid, you can see the light reflected from the colloid. • Suspension—a heterogeneous mixture containing a liquid in which visible particles settle. • Ex. Mud in a pond & river deltas

  5. How to Classify Matter Element Substance Compound Matter Heterogeneous Mixture Homogeneous or solution On Periodic table Ex. Water= h20 *suspension *colloid

  6. Sec. 2: Properties of Matter • Physical Properties—any characteristic of a material that you observe without changing its substances. • Ex. Color, shape, size, melting & boiling point • Some physical properties describe behavior. • Magnetism, conduct electricity, viscosity, dissolving. • You can separate mixtures using physical properties. • Size, color, magnetism, boiling point, etc.

  7. Physical Changes • Physical change—a change in size, shape, or state of matter (solid, liquid, gas) • The identity of the substance doesn’t change. • Ex. Freezing, ripping, folding, dissolving.

  8. Chemical Properties • Chemical Property—a characteristic of a substance that tells if it can undergo a certain chemical change. • Ex. Flammability, reaction to light

  9. Chemical Changes • Chemical Change—a change of 1 substance to another. • Ex. Rotten eggs, rust, burning. • Detecting Chemical Changes: • Odor, heat, light, sound, release gas (bubbles) • Separating Substances: • Ex. Cleaning tarnished silver, purifying metals. • A chemical change will change the substances, so it cannot be used to separate a mixture.

  10. Weathering • Weathering is how Earth’s surface changes. • Weathering is a result of both physical & chemical changes. • Physical: ice wedging (ice in cracks expands & breaks the rocks), & streams cut through softer rock. • Chemical: limestone dissolves in acidic ground water (canyons & caves are formed this way)

  11. Caves are formed through chemical weathering. Ice wedging or the freeze/thaw cycle breaks rocks into pieces

  12. Conservation of Mass • Law of Conservation of Mass—the mass of all substances before a chemical or physical change equals the mass of all substances after the change. • In other words: mass is neither created nor destroyed during any chemical or physical change.

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