Review. 8th grade science STAAR. Name Class. Underline your strong TEKS and circle your weak TEKS: 8.5A Atoms. 7.5C Energy Flow Through Ecosystems

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1 8th grade science STAAR Review Name Class Underline your strong TEKS and circle your weak TEKS: 8.5A Atoms 7.5C Energy Flow Through Ecosystems 8.5B Reactivity 8.5C Periodic Table 8.5D Chemical Formulas 8.5E Chemical Reactions 8.5F Balanced Equations 7.6A rganic Compounds 7.6B Physical/Chemical Changes in Digestion 6.5C Elements vs. Compounds 6.6A Metals, Nonmetals, and Metalloids 6.6B Density 2014 Science Teaching Junkie, Inc. 1

2 Reporting Category 1: Matter and Energy Atoms 8.5A Fill in the missing information to summarize what you know about atomic structure. Name of Subatomic Location within the Atom Electrical Charge Relative proton inside the nucleus positive 1 amu neutron inside the nucleus neutral 1 amu electron outside the nucleus; in the electron cloud negative 1/1836 amu; almost zero Bohr Model Draw an atom that has five protons, six neutrons, and five electrons. Complete the color key to identify the three major subatomic particles, then answer the 2 questions that follow. CLR KEY Protons Neutrons Electrons What is the mass of the atom in this model? 11 amu What is the electrical charge of the atom in this model? neutral; no charge What subatomic particle determines the identity of an element? proton The diagram below shows models of four different atoms. Use the models to answer the following questions: A B C D Which atom has the greatest mass? D Which atom(s) have a neutral electrical charge? A & C Which atom(s) have a positive electrical charge? D Which atom(s) have a negative electrical charge? B 2014 Science Teaching Junkie, Inc. 2

3 Reactivity 8.5B Fill in the table below to identify the number of valence electrons for each group/family on the periodic table. Group/Family Number No. of Valence Electrons Which atom below is the most reactive? Explain why. Atom A, because it has one valence electron that it needs to lose Which atom below is inert or nonreactive? Explain why. Atom B, because it has 8 valence electrons (a full outer shell). P: 11 N: 12 P: 18 N: 22 P: 15 N: 16 Atom A Atom B Atom C f the elements N,, Cl, Na, and S, which two would likely have similar chemical properties? Why? xygen () and sulfur (S) will have similar chemical properties because they are in the same group/ family on the periodic table. Periodic Table 8.5C & 6.6A The atomic number is equal to the number of. protons The atomic mass number is equal to the protons plus the. neutrons The horizontal (lefttoright) rows of elements on the periodic table are called, periods which indicate the number of energy levels (shells) in an atom of those elements. There are 7 (#) of these rows on the periodic table. The vertical columns (upanddown) of the periodic table are called groups or. families There are 18 (#) of these columns on the periodic table. All of the elements in each column have similar chemical properties because they each have the same number of. valence electrons 2014 Science Teaching Junkie, Inc. 3

4 Circle the correct description in each row below to identify the properties of metals, nonmetals, and metalloids. Metals Location on Periodic Table: left of zigzag line / along zigzag line / right of zigzag line Luster: shiny / dull / varies (some are shiny, some are dull) Conductivity: good conductors of heat and electricity/ poor conductors / varies Malleability: able to be hammered into thin sheets / brittle / varies Most reactive metal group on periodic table is found in: Group 1 / Group 17 / Group 18 NonMetals Location on Periodic Table: left of zigzag line / along zigzag line / right of zigzag line Luster: shiny / dull / varies (some are shiny, some are dull) Conductivity: good conductors of heat and electricity/ poor conductors / varies Malleability: able to be hammered into thin sheets / brittle / varies Most reactive nonmetal group on periodic table is found in: Group 1 / Group 17 / Group 18 Metalloids Location on Periodic Table: left of zigzag line / along zigzag line / right of zigzag line Luster: shiny / dull / varies (some are shiny, some are dull) Conductivity: good conductors of heat and electricity/ poor conductors / varies Malleability: able to be hammered into thin sheets / brittle / varies n the Periodic Table below: Shade the group of elements that are called the Noble Gases red. Shade all of the elements in Period 4 blue. Circle three elements that are classified as metals. Draw a triangle around three elements that are classified as metalloids. 2 He 3 Li Be 10 Ne 11 Na 19 K 12 Mg 20 Ca 21 Sc 22 Ti Cr 25 Mn 26 Fe 27 Co 28 Ni 29 Cu 30 Zn Cl 31 Ga 32 Ge 33 As 34 Se 35 Br 18 Ar 36 Kr 37 Rb 38 Sr Zr 41 Nb 42 Mo 43 Tc 44 Ru 45 Rh 46 Pd 47 Ag 48 Cd 49 In 50 Sn 51 Sb 52 Te Xe 55 Cs 87 Fr 56 Ba 88 Ra 57 La 89 Ac 72 Hf 104 Rf 73 Ta 105 Db Re 106 Sg 107 Bh 76 s 108 Hs Pt 109 Mt 79 Au 80 Hg 81 Tl 82 Pb 83 Bi 84 Po 85 At 86 Rn Use a periodic table to identify the following elements. Identify the metal in period 3 that is more reactive than magnesium: sodium (Na) Identify the noble gas with 2 valence electrons: helium (He) Identify the element in group 17 with 5 energy levels or shells: iodine (I) Identify the element that has more valence electrons than fluorine and fewer energy levels than sodium: neon (Ne) Identify the metalloid in period 3 with more protons than sodium and fewer valence electrons than chlorine: silicon (Si) 2014 Science Teaching Junkie, Inc. 4

5 Chemical Formulas 8.5D & 6.5C A coefficient tells you how many molecules there are. A subscript tells you how many atoms there are. Fill in the missing information to complete the chart. Substance H 2 Cu 4 CaC 3 Zr Ca 3 (P 4 ) 2 2C Check ne Box Check ne Box Fill out each of these boxes. Chemical Symbol Chemical Formula Element How many atoms of each element are in each formula? H22; Hydrogen: ; 2 xygen: 2 Compound H2S4; Hydrogen: ; 2 Sulfur: ; 1 xygen: 4 Total # El C(NH2)2; Carbon: ; 1 xygen: ; 1 Nitrogen: ; 2 Hydrogen: 4 12 How many atoms of oxygen are present in two molecules of glucose (C6H126)? Chemical Reactions 8.5E List 4 signs that a chemical reaction has occurred. 1. temperature change formation of light 2. change in color (unexpected) change in odor 3. gas formation 4. formation of a precipitate State whether each of these changes is physical (P) or chemical (C). Chopping wood: P Burning paper: C Boiling water: P Tarnishing metal: C Spoiling milk: C Candle wax melting: P Baking a cake: C Dissolving sugar in water: P Cracking eggs: P 2014 Science Teaching Junkie, Inc t Total # t Total # lecul

6 While conducting many different labs over the school year, a student recorded observations in her science journal. Circle all of the following observations that would be considered evidence of a chemical reaction taking place. a) When the 2 clear, colorless solutions were combined, the result was a blue liquid. b) Solution #1 evaporated quickly. c) Some of liquid #2 froze into ice crystals. d) Some of the powder dissolved in the first beaker. e) After the liquids combined, the temperature dropped by 3 C. f) The baking soda and hydrochloric acid combined, forming bubbles. g) The powder absorbed some of the acid. h) The two liquids combined, forming a solid substance that sank to the bottom of the test tube. Balanced Equations 8.5F Label the following parts of the chemical equation below: coefficient, subscript, products, reactants, yields, chemical formula. A. reactants B. yields C. products D. subscripts E. chemical formula F. coefficient The Law of Conservation of Mass states that during a chemical reaction, mass/matter is not created or. destroyed Because of this law, there must be exactly the same number and kind of atoms on each side of a chemical equation. To check if an equation is balanced or not, simply count the number of atoms of each element on the reactant side of the equation and check to see if there are the same number of atoms of each element on the products side of the equation. If so, it is balanced. Which of the following chemical equations is balanced? A. Al CuCl2 AlCl3 Cu B. 2Al 3CuCl2 2AlCl3 3Cu C. 3Al 2CuCl2 3AlCl3 2Cu D. 4Al 3CuCl2 4AlCl3 3Cu Which of the following chemical equations is balanced? A. K3P4 2HCl 2KCl 2H3P4 B. K3P4 3HCl KCl H3P4 C. K3P4 HCl KCl H3P4 D. K3P4 3HCl 3KCl H3P Science Teaching Junkie, Inc. 6

7 Energy Flow Through Ecosystems 7.5C Highlight one complete food chain on the food web. Which organisms on the food web have the most available energy? plants/producers Which organisms on the food web have the least available energy? Give their names. coyote & hawk Draw arrows on the energy pyramid to show the direction of energy flow from greatest to least. n the pyramid, color producers green, herbivores yellow, and carnivores red. nly about % 10 of the energy from one level of the energy pyramid is used to support the level above it. Almost all of the energy that supports life on Earth comes from. the Sun A B C D The process that plants use to capture the radiant energy from the sun and turn it into chemical energy is called. photosynthesis rganic Compounds 7.6A An organic compound has one or more carbon atoms as part of the molecules structure. ther elements found in the organic compounds of living organisms include: hydrogen (H), oxygen (), nitrogen (N), sulfur (S), and phosphorus (P). Check one. Substance Formula rganic Inorganic sugar C 6 H 12 6 methane water 2014 Science Teaching Junkie, Inc. 7

8 Physical/Chemical Changes in the Digestive System 7.6B Place check marks in the appropriate boxes below to indicate the type(s) of changes that occur during the digestive process in the organs shown. Note: it is possible to have a check mark in both columns. Structure Mouth Stomach Small Intestine Physical Change Chemical Change Density 6.6B The formula to calculate density is density = mass volume Use the pictures of the triple beam balance and graduated cylinder to find the density of the rock. (Show all work!) The mass of the rock when placed on the balance: SHW WRK HERE: d = m/v d = 125 g/ 10 cm 3 d = 12.5 g/cm 3 10 ml = 10 cm 3 A sample of metal has a mass of 23.4 g and a volume of 3.0 ml. What is the sample s most likely identity? A. Aluminum (2.8 g/ml) B. Gold (19.3 g/ml) C. Iron (7.8 g/ml) D. Copper (8.9 g/ml) What is the density of a substance with a volume of 5.0 ml and a mass of 15.0 g? A g/ml B. 3.0 g/ml C g/ml D g/ml 2014 Science Teaching Junkie, Inc. 8