2014 – 15 8th Grade 2nd Nine Weeks Benchmark Study Guide
Scientific Investigation:
PS 1b: Select appropriate equipment:
 Triple beam balance: measure mass
 Thermometer: measures temperature
 Ruler: measures length
 Graduated cylinder: measures liquid volume
 Spring scale: measures force
PS1c: Recognize metric prefix units and make common metric conversions between the same base metric units
 Basic Metric Unit of Measure: mass: gram
volume: liter
length: meter
 Prefixes: see chart below
 Metric Conversions
King ---- Henry ---- Died ---- By ---- Drinking ---- Chocolate ---- Milk
Kilo ---- Hecto ---- deka ---- base ---- deci ---centi ------ milli
Example: 35 km = 3500000 cm (centi is 5 places to the right of kilo so you move the decimal 5 places to the
right) a whole number has an imaginary decimal at the end (35.)
PS 1f: Identify the key components of controlled experiments: hypotheses, independent and dependent variables, constants,
controls, and repeated trials.
Scientific Investigation:
 Independent Variable: the factor that is purposely changed by the scientist 
 Dependent Variable: the responding variable (changes because of the independent variable), what we measure 
 Constants: the factors that stay the same in each trial 
 Control: standard for comparison (the one without the independentvariable or1 of the levels of IV)

 Repeated Trials: the number of times you conduct the entire experiment. 
 Conclusion: the outcome, analyze the data and determine if your hypothesis was supported. 

Example: Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50
workers each and assigns each group the same task (staple a set of papers). Group A is given the special juice to drink while
they work. Group B is not given the special juice. After an hour Smithers counts how many stacks of papers each group has
made. Group A made 1587 stacks, Group B made 2113 stacks.





Independent Variable: special juice
Dependent Variable: amount of productivity (number of stacks)
Control: Group B, the group that was not given the special sauce.
Constants: the task, size of group, staplers.
Conclusion: the hypothesis was not supported by the data.
PS 1i: Use a variety of graphical methods to display data. Create an appropriate graph for a given set of data. Select the
proper type of graph for a given set of data, identify and label the axes and plot data points.
X axis: independent variable
Y axis: dependent variable
Frequency is the dependent variable. College major is the independent variable
PS 1j: Formulate conclusions that are supported by gathered data.
This experiment had 5 repeated trials. The independent variable is the time batteries charged. The dependent variable is the
distance the remote control car traveled. Conclusion: the longer the batteries charged the further the car traveled.
Chemical Bonds and Change:
PS2b: Matter
 Define compounds as inorganic or organic: all organic compounds have Carbon, chemical symbol C.
 Analyze the pH of a solution and classify it as acidic, basic, or neutral.
I.
Acid and Bases:
a. Basicity – the level of base a substance is. Bases have a pH over 7

Examples of bases: baking soda, ammonia
 Taste bitter, slippery, have hydroxides (OH-)
 Turns red litmus paper blue
 Neutralizes acids to form salt and water
b. Acidity – the level of acid a substance is. Acids have a pH under 7
 Examples: Lactic acid: buttermilk, acetic acid: vinegar, citric acids: oranges
 Tastes sour
 Feels oily
 Reacts with metals and carbonates
 Corrosive
 Turns blue litmus paper red
 Chemical formula begins with H except water (H20) and peroxide (H202)
c. Neutral: pH of 7
d. The products of a neutralization reaction are water and salt. Vinegar + Baking Soda  Water + Salt + CO2
e. Identifying a compound as an acid, base or salt.
H in the front is an acid: HCl
H in the back is a base: KOH
No H is a salt: NaCl, CO2
Acids increase in strength as you move closer to 0, bases increase in strength as you move closer to 14.
A strong acid would have a pH between 0 and 3. A strong base would have a pH between 12 and 14.
PS 2d and e: Distinguish between physical and chemical properties. Find the mass and volume of substances and compare
their densities. Density = Mass/Volume
 Physical Properties: shape, density, solubility, odor, melting point, boiling point and color.
 Chemical Properties: acidity, basicity, combustibility and reactivity.
PS 4c: Recognize that the number of electrons in the outermost energy level determines an element’s chemical properties or
chemical reactivity.
 Categories of Elements:
Metals are to the left of the stair-step; non- metals to the right, metalloids are along the stair-step.
 Groups/Families: elements in the same group have the same number of valence electrons (chemical properties)
 Alkali Metals – group 1 – number of valence electrons 1
 Alkaline Earth Metals – group 2 – number of valence electrons 2
 Transition Metals (short columns in the center) – do not follow the valence electron rule
 Boron Family – group 13 – number of valence electrons 3
 Carbon Family – group 14 – number of valence electrons 4
 Nitrogen Family – group 15 – number of valence electrons 5
 Oxygen Family – group 16 – number of valence electrons 6
 Halogens - group 17 – number of valence electrons 7
 Noble Gases - group 18 – number of valence electrons 8
 Period: represents the number of energy levels (electron shells).
 Noble Gases have 8 valence electrons – its outer shell is full (happy) so the noble gases are non-reactive/do not
normally create bonds.
 Octet Rule: atoms tend to lose/gain or share electrons in order to have a full outermost (valence) shell.
PS 4c: Predict what kind of bond will likely form (ionic or covalent) when metals and non-metals combine chemically.
 Ionic Bonds: Metal and Non-metal: The metal loses a valence electron to the non-metal.
Example: NaCl forms an ionic bond because Na (sodium) is a metal and Cl (chlorine) is a non-metal
 Covalent Bonds: Non-metal to Non-metal: the two non-metals share valence electrons.
Example: CO2 forms a covalent bond because C (carbon) and O (oxygen) are both non-metals.
PS 4c: Describe the difference between ionic and covalent bonding.
 Ionic Bonding: Metal loses valence electron(s) and becomes a positive ion. Non-metal gains the electron(s) and
becomes a negative ion. The opposite charges form an attraction creating the ionic bond.
Example: Na has 1 valence electron and Cl has 7. Na will transfer its valence electron to Cl, Na now has a +1
charge and chlorine has a -1 charge. The opposite charges attract forming the ionic bond. The oxidation numbers
add up to 0 so we have a stable compound. Group 1 wants to bond with Group 17 to create a full (8) valence shell.
Example: Mg has 2 valence electrons and Oxygen has 6 valence electrons. Mg gives its 2 valence electrons and
become +2 charge, oxygen gains the 2 valence electrons and becomes -2 charge. MgO forms an ionic bond.
Picture: NaCl ionic bond

Covalent Bonding: two non-metals share valence electrons so each has a full (8) valence shell.
Example: 2 hydrogen atoms share their valence electron
Example: CO2 (carbon dioxide)
Carbon Dioxide example using Lewis Dot Structure
PS 4c : Given a chemical formula, identify the elements and the number of atoms of each that comprise the compound.
PS 5b: Identify the reactants and products in a given chemical equation formula, given chemical formulas, write and balance
simple chemical equations.
 Counting Atoms and Balancing Chemical Equations
a. NH3: is an example of a chemical formula. 3 is a subscript, it applies to the element that it is behind. In this
formula there is 1 N (nitrogen) atom and 3 H (Hydrogen) atoms.
b. 2NH3: is an example of a chemical formula. The 2 is a coefficient, it applies to the entire compound (tells
you how many atoms of NH3), in this example there are 2 atoms of N and 6 atoms of H.
c. 2Na(OH)2 : when a subscript follows a parenthesis the subscript applies to everything within the
parenthesis. Notice this example also has a coefficient. The atom counts would be: 2- Na, 4- O and 4- H.
d. Chemical Equations:
H2 + O ----> H2O
Reactant----> product
The arrow points toward the product. The product is the new substance.
e. The Law of Conservation of Matter (mass): matter cannot be created or destroyed in a chemical reaction.
This means that you must have the same number of atoms of each element on both sides of a chemical
equation.
f. Balancing chemical equations: you may not change the subscripts you may only change the coefficients. Be
sure to re-count your atoms each time you change a coefficient when balancing an equation.
Balancing Example:
MnO2 + HCl ----- MnCl2 + H2O + Cl
MnO2 + 4HCl -- MnCl2 + 2 H2O + 2Cl
PS 5a: Design an investigation that illustrates physical and chemical changes.
 Physical: shape, density, solubility, odor, melting point, boiling point, and color.
Ex. Solubility is the amount of a solute that will dissolve in a solvent.
 Chemical: acidity, basicity, combustibility and reactivity (ability to form other substances)
Examples: When a chemical change is taking place a new substance is created – rust, a new compound like NaCl.
Evidence of a chemical reaction may include a change in temperature, release of a gas (bubbling), combustion,
substance is an acid or base.
PS 5b: Analyze Experimental Data to determine whether it supports the Law of Conservation of Mass.
 A balanced chemical equation supports the Law of Conservation of Mass
 Example: station lab on Law of Conservation of Mass – the mass of the reactants (baking soda and vinegar) was the
same as the mass of the products.
PS 5b: Recognize that some types of chemical reactions require continuous input of energy (endothermic) and others
release energy (exothermic.
 Endothermic: energy is absorbed in the reaction. Endothermic Equation: A + B + energy - AB
Heat is absorbed in the reaction (temperature goes down)
 Exothermic: energy is released during the reaction. Exothermic Equation: A + B  AB + energy
Heat is released (temperature goes up)
Graphs for Exothermic and Endothermic Reactions
PS 5b: Compare and Contrast Physical, chemical and nuclear changes:
 Physical change: the substance does not change only its appearance. Example: tear a piece of paper
 Chemical change: the substance is changed. Example: Iron and Oxygen combine to create rust, Sodium and
Chlorine combine to form sodium chloride (table salt)
 Nuclear Change: a different element is formed by either splitting or joining the nucleus. Example: fusion of
Hydrogen nucleus creates Helium.
PS 5c: Describe in simple terms, the processes that release nuclear energy (i.e. nuclear fission and nuclear fusion) Create a
simple diagram to summarize and compare and contrast these two types of reactions.
 Nuclear energy is the energy stored in the nucleus of an atom. The energy can be released by joining atoms’ nuclei
together (fusion) or by splitting atoms’ nuclei (fission) resulting in the conversion of a small amount of matter into
large amounts of energy. Good thing: large amount of energy from a small amount of energy. Bad thing: radioactive
nuclear waste storage and disposal.
 Nuclear Fusion: joining of the nuclei of two or more atoms.
Nuclear Fission: splitting of the nuclei
occurs on the sun
(a chain reaction) used in nuclear power plants
Advantages
 A large amount of energy from a small amount of matter
 Nuclear power plants can produce low cost, long lasting energy (inexpensive)
 Does not produce a lot of pollution
 Does not use fossil fuels
 Fuel is readily available (easy to get)
Disadvantages
 Fission produces radioactive waste (fusion does not)
 Waste is hazardous to handle and must be buried for 1000’s of years
 Accidents can be a major disaster
 Fusion: difficult to produce because extremely high temperatures are needed
Additional content from the 1st Nine Weeks to be tested
PS 3b: Differentiate among the three basic particles in the atom (proton, neutron, electron) and their charges, relative
masses and locations. Compare the Bohr atomic model to the electron cloud model with respect to their ability to represent
accurately the three-dimensional structure of the atom.
Modern Atomic Model: has an electron cloud (3 dimensional model, more accurate)
_________________________________________________________________________________________________
Bohr Model: electrons travel in specific orbits
_________________________________________________________________________________________________________
Atomic structure:
Protons = positive charge (found in the nucleus)
Neutrons = neutral charge (found in the nucleus)
Electrons = negative charge (found in the electron cloud/orbit)
 Most of the mass of the atom is in the nucleus (protons + neutrons), the electron is so small with very little mass
(not counted in the mass of the atom)
Mass = protons + neutrons

6th Grade Content to be tested:
SOL 6.5a: Investigating the Unique Properties of Water. Design an investigation to demonstrate the ability of water to
dissolve material.
 Water is the Universal Solvent: water has the ability to dissolve many substances because it is a POLAR MOLECULE.
 Polar means that the molecule has a positive end and a negative end. Opposites attract so when a polar substance
comes into contact with another polar substance – the charges attract to each other and the substance dissolves.
 Hydrogen end of the water molecule is positive, the oxygen end is negative
 Solvent: the substance doing the dissolving
Solute: the substance being dissolved
Water Molecules: shows positive and negative charges

Oil is non-polar and will not dissolve in water.
SOL 6.8e: Investigating Watersheds: The health of ecosystems and the abiotic factors of a watershed.
 Ecosystem: all the biotic communities that live in an area together with the abiotic factors in the environment
 Abiotic: a non-living part of the environment
 Watershed: a region or area where water travels downhill and ultimately drains into a large body of water
 The health of an ecosystem is directly related to water quality.
 Human activities can affect the health of the watershed: deforestation (cutting down trees, plowing cropland) can
lead to soil erosion, pesticides use and animal waste can lead to pollution in the water. Soil and chemicals (from
factories) entering the water can decrease the turbidity (clarity) of the water, the pH of the water is also affected. If
the water is too cloudy then sunlight cannot penetrate providing needed solar energy to plants under the water.
Pollution of a Watershed
A Watershed
SOL 6.8e: Interrelationships in Earth/Space Systems: Model and describe how day and night and the phases of the moon
occur.
 Day: the side of the Earth facing the sun
Night: the side of the Earth away from the sun
 Phases of the Moon: I left my car in the wane, I had to wax it to make it right. When the sun is reflected on the left
side of the moon = waning, when the sun is reflected on the right side of the moon = waxing.
7th Grade Content to be tested
LS 2d: Investigating Cell Theory: Design an investigation from a testable question related to animal and plant cells. Example:
Do onion cells vary in shape or structure depending on where they are found in the plant?
Comparison of Plant and Animal Cells
LS 3b: Investigating Cellular Function and Cell Reproduction:
 Explain the role that each life function serves for an organism: ingestion, digestion, and removal of wastes, stimulus
response, growth, repair, gas exchange, and reproduction.
 Model how material move into and out of cells in the processes of osmosis, diffusion and selective permeability.
 How changes in available materials might affect particular life processes in plants and animals.
 Understand cellular organization, emphasis on observations of cells and tissue.
LS 6b: Investigating Energy Flow
 Classify organisms found in local ecosystems as producers or first, second or third level consumers. Design and
construct models of food webs with these organisms.
LS 13b: Investigating Evolution
 Describe and explain how fossils are records of organisms and events in the Earth’s history.
 Explain the evidence for evolution from a variety of sources of scientific data.
Picture: evolution of horse leg: Equus is the modern day record.