Chapter 9 Review

Substances A substance is either an element of a compound. An element is a kind of matter in which all atoms are alike. Examples – Hydrogen, Carbon, Fluoride A compound is a material made of two or more elements that are combined. Examples – H2O, CO2 An atom is a particle that makes up all matter.

Mixtures A mixture is a material made up of two or more substances. Mixtures do not always contain the same amounts of different substances. Heterogeneous mixture – a mixture in which different materials can be easily distinguished Example – A solution with oil and water Homogeneous mixture (solution) – a mixture in which two or more substances are uniformly spread out. Example – A solution of salt and water.

Colloids and suspensions A colloid is a heterogeneous mixture that, like a solution, never settles. Examples – Gelatin, milk A suspension is a heterogeneous mixture containing a liquid in which visible particles settle. Examples – Muddy water

Tyndall Effect The scattering of light by particles in a mixture. We can see the Tyndall effect in colloids.

Smog Smog is a form of air pollution. It is a colloid of small invisible pieces of solid materials mixed with the gases that make up air. Some of the solid particles that make up smog are dust. Unburned compounds in automobile exhaust accounts for most of the particles in smog. Warm air rises in the atmosphere. However, this warm air may be trapped beneath a layer of colder air. The combination of the warm and cold air cause the colloid smog.

Smog vs. Fog Kind of Air Pollution Cloud Bank Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide Fog begins to form when water vapor condenses into tiny liquid water droplets in the air. It can inflame breathing passages, decreasing the lungs' working capacity, and causing shortness of breath, pain when inhaling deeply, wheezing, and coughing Fog reduces visibility and thus contributes to accidents, particularly with modes of transportation.

Physical properties A physical property is any characteristic of a material that you can observe without changing the substances that make up the material. Appearance and behavior Shape Color Size Density Melting point Boiling point

Physical Change A change in size, shape or state of matter. When a substance freezes, boils evaporates, sublimes or condenses, it undergoes physical change. A color change indicates a physical change. Physical changes do not change the identities of the substances in a material.

Chemical Change A change of one substance in a material to a different substance. Examples include: Fireworks exploding Matches burning Rotten eggs Burned toast Rusty tires (exposed to oxygen) Odor is a clue that a chemical change has occurred. Burning and rusting are chemical changes because new substances are produced.

Chemical Properties A characteristic of a substance that indicates if it can undergo a certain chemical change. Flammable or combustible substances.

Law of Conservation of Mass Matter is neither created nor destroyed during a chemical change. When we burn something, there is no loss of mass. (Add the oxygen in the air with the log that burned)