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Chemistry Guide #2
8th Grade Earth Science
| Question | Answer |
|---|---|
| Physical Changes: | A change in the form or appearance of a sample of matter, but does NOT change its composition. -Changing from a solid, to a liquid, to a gas, or to a plasma (or the reverse). -Change in shape or size. -A substance dissolving into another substance. |
| Chemical Changes: | A change in the composition of a substance – a chemical reaction. -Changes color -Gives off a gas/odor -Heat is produced -Heat is absorbed -A solid is produced |
| Describe the columns of the Periodic Table. | Columns = group or family The elements in each group have the same number of electrons valence electrons (in outer shell). - have similar chemical and physical properties |
| Describe the rows on the Periodic Table. | Rows- periods All of the elements in a period have the same number of atomic orbitals. Add one as you go down, –The properties gradually change predictably across the period. |
| Where are the metals, metalloids, & nonmetals are located on a Periodic Table? | Nonmetals- top right, everything right of metalloids Metalloids- dividing the nonmetals and metals, diagonal line. B, Si, Ge, As, Sb, Te, Po Metals- everywhere else |
| Where are the different families found on a Periodic Table? | Left-Right Alkali Metals, Alkaline Earth Metals, Transition Metals, Post Transition, Metalloids, Other Metals, Halogen, Noble Gas |
| What is the octet rule? | 8 electrons fill a valence shell results in a stable atom |
| What are ions? | atoms that have gained or lost electrons resulting in a charge. Positive- cations Negative- anion |
| How do ionic compounds form? | Bonds formed by the attraction between oppositely charged ions. metal - nonmetal |
| How do covalent compounds form? | Bonds formed by sharing electrons between atoms to fill the valence shell. nonmetals - nonmetals (or metalloids) |
| What is a polar covalent compound? | Uneven sharing of electrons in a covalent bond. Results in the compound having a positive end & a negative end. EXAMPLE: Water. The Oxygen end is slightly negative while the Hydrogen end is slightly positive. |
| What are the parts of a chemical equation? | Reactants- substances that exist before the reaction begins. Products- substances that form as a result of the reaction. |
| What is the difference between exothermic & endothermic reactions? | Exothermic- Heat or light energy is released from the reaction causing the temperature of the substances to increase. Endothermic- Heat or light energy is absorbed causing the temperature of the substances to decrease. |
| How does the Law of Conservation of Mass apply to chemical reactions? | The mass of the products must be equal to the mass of the reactants, because matter cannot be created or destroyed - it just changes its form. |
| How does temperature, concentration, surface area, and catalysts affect the rate of a chemical reaction? | Hotter temperature, more concentration, more surface area, and adding a catalyst speeds up the reaction. |
| Give a general description of the organization of the Periodic Table. | It is organized as a chart, with rows and columns. * Arranged according to atomic number and similar properties. |
| Inhibitors vs. Catalyst | Inhibitors are substances that are added to a reaction to slow the reaction process Catalysts are the substances added to a reaction to speed up the reaction processes. |
| Reactivity | Metals: Period: reactivity decreases as you go from left to right Group: reactivity increases as you go down a group. Nonmetals: Period: reactivity increases as you go from left to right Group: reactivity decreases as you go down a group. |
| Metals | Most of the elements are solid metals. –Metals are usually shiny, malleable, good conductors of heat & electricity and ductile. |
| Metalloids | –Elements that have some characteristics of both metals & nonmetals. |
| Nonmetals | Most nonmetals are gases. –Solid nonmetals are brittle, poor conductors, & not easily shaped. –97% of your body is made of nonmetals |
| Alkali Metals | Most reactive of the elements. – Not naturally found by itself. – Has a single electron in its outermost shell. |
| Alkaline Earth Metals | Commonly used in fireworks for the colors. – Has 2 electrons in the outermost shell. |
| Transition Elements | – Middle of the periodic table |
| Halogens | Bond with Alkali Metals to form salts. – Have 7 electrons in outermost shell. – Steal electrons from other atoms. |
| Noble Gases | Only naturally stable elements. – Have a full outermost shell of electrons (8) – Found in small amounts in the atmosphere. – Heated to produce colorful light. |
| Physical Properties: | Characteristics that can be observed without changing the composition of the substance. Color Phase,State Size, Shape, Volume Viscosity Freezing, Melting Boiling, Condensation Mass Density |
| Chemical Properties: | A characteristic that can only be determined by changing the chemical identity of a substance. Flammability (catches on fire) Combustibility (explosive) Luminescence (produces light) Oxidation (rusting) Level of Reactivity |
Created by:
*BROOKE*
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