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Chemistry Guide #2

8th Grade Earth Science

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*