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Fall Mid-Term Review: 8th grade 2016 – Student Packet
TEKS and Concepts Covered:
Unit 1 Scientific Investigations:
8.2A plan and implement comparative and descriptive investigations by making observations, asking well-defined questions, and using
appropriate equipment and technology
8.2B design and implement experimental investigations by making observations, asking well-defined questions, formulating testable
hypotheses, and using appropriate equipment and technology;
8.2C collect and record data using the International System of Units (SI) and qualitative means such as labeled drawings, writing, and
graphic organizers;
8.2D construct tables and graphs, using repeated trials and means, to organize data and identify patterns
8.2E analyze data to formulate reasonable explanations, communicate valid conclusions supported by the data, and predict trends.
2.1 Structure of the Atom/Periodic Table:
8.5A describe the structure of atoms, including the masses, electrical charges, and locations, of protons and neutrons in the nucleus
and electrons in the electron cloud
8.5B identify that protons determine an element’s identity and valence electrons determine its chemical properties, including reactivity
8.5C interpret the arrangement of the Periodic Table, including groups and periods, to explain how properties are used to classify
elements
2.2 Chemical Equations:
8.5D recognize that chemical formulas are used to identify substances and determine the number of atoms of each element in chemical
formulas containing substances
8.5F recognize whether a chemical equation containing coefficients is balanced or not and how that relates to the law of conservation
of mass
8.5E investigate how evidence of chemical reactions indicate that new substances with different properties are formed
Review Material from prior years:
6.5A-D elements, elements that comprise earth and surroundings, compounds, identify the formation of a new substance
7.6A identify that organic compounds contain carbon, hydrogen, oxygen, phosphorus, nitrogen or sulfur
6.6A compare metals, nonmetals and metalloids
6.6B calculate density to identify an unknown substance
7.6A identify that organic compounds contain carbon, hydrogen, oxygen, phosphorus, nitrogen or sulfur
3.1 Force and Motion:
8.6B differentiate between speed, velocity, and acceleration
8.6A demonstrate and calculate how unbalanced forces change the speed or direction of an object’s motion
8.6C investigate and describe applications of Newton’s law of inertia, law of force and acceleration, and law of action-reaction such as
in vehicle restraints, sports activities, amusement park rides, Earth’s tectonic activities, and rocket launches
Review Material from prior years:
6.8.A compare and contrast potential and kinetic energy
How and What to Study:
Everything from this semester that we have covered is on the exam in one way or another.
 Complete this review and study prior test reviews, along with unit overviews.
 Know vocabulary terms and the context to use them in.
 Review power points posted in each unit.
 Look through your textbook for the same content.
 Look over warm up questions (look in the warm up section on teacher’s website). Warm
up questions are similar in style and depth to test questions.
 On the landing page of the teacher’s website, there is a button to click that leads to a
review page just for this mid-term. It has review websites, power points, videos and
articles to enhance your understanding of these topics.
 Make flash cards, form study groups, quiz yourself and others – actively study (not
passively)!
Scientific Investigations: Questions for Review -
1. Explain what an experiment is:
2. What are the steps of the scientific method?
3. Define the problem or question:
4. Which step requires you to use your senses? ____________________________________
5. Define hypothesis:
6. What is data? __________________________________________________________________
7. What are the two types of data and explain the difference between them:
8. Explain what a variable is:
9. Explain the two (main) types of variables:
Independent variable:
Dependent variable:
10. Read the following scenario and come up with a question and a testable hypothesis:
Ali’s favorite food is microwave popcorn. She loves microwave popcorn so much that she can’t
stand to waste the unpopped kernels in the bottom of the bag. The next time Ali goes to the
grocery store, she buys all of the brands of microwave popcorn that the store has.
Possible question:
Possible Hypothesis:
11. Why are graphs used to show data results?
12. In laboratory experiments, you will usually be controlling one variable and seeing how it affects
another variable. What does a line graph show?
13. What is a possible conclusion you could make from the graph below?
A. Ice cream is not as loved as much as those frozen prepared meals
B. The purchases of juice is lower by about half of the money spent on vegetables
C. Vegetables are more expensive than ice cream and desserts
1. Mass is defined as ____________________________________________________.
2. Mass is measured with a triple-beam balance in units of ____________________.
3. What is the mass of the object using the triple beam balance image below? _______________
4. Volume is defined as ________________________________________________________
5. Volume can be measured with a _______________________ if the object is regularly shaped,
like a cube. But volume can also be measured with a ________________
_________________ using water displacement if the object is irregular in shape.
6. What is formula for volume when using water displacement? __________________________
7. What is the volume of the object above? __________________________________________
8. What is the volume of this cube? ___________________
5 cm
Example Test Questions:
1.
In the above picture, an object is placed into containers of water with different
temperatures. The object will sink down further as the water temperature increases. Which
statement explains why the object moves down as the water temperature increases?
a.
b.
c.
d.
The
The
The
The
object becomes more dense
water becomes more dense
object becomes less dense
water becomes less dense
2.
In an experiment, the variable that changes as a result of manipulating the independent
variable is the __________________________ ?
a. Hypothesis
b. Controlled variable
c. Dependent variable
d. Independent variable
3.
Your teacher hands out a copy of a laboratory experiment. What is the first thing you
should do to conduct the experiment safely?
a. Gather supplies
b. Begin heating any materials that need to be hot
c. Pre-mix your substances to save time
d. Read the procedure before starting
4.
In a controlled experiment, a scientist is studying how long it takes pea plants growing in
different soil types to develop flower buds. What is the independent variable?
________________________________________________________________________
5.
What is the purpose of collecting data?
a. To show time increments
b. To see if the data supports the hypothesis
c. To develop a good beginning question
d. To determine the order of your procedures
Atomic Structure and the Periodic Table: *remember to review your test review from
this Unit!
What to know: Matter is composed of atoms and has chemical and physical properties.
 Matter is made of particles that are in constant motion.
 Subatomic particles
 Protons, electrons, neutrons
 Atomic mass
 Atomic mass includes the total mass of the protons, neutrons, and electrons in an atom of
an element
 Mass of protons, neutrons, and electrons –give mass
Atomic mass on the periodic table is an average of all the forms of an element
 The mass of electrons is so small compared to the protons and neutrons that it has little
effect on the atomic mass
 Electrical charges
 Positive = proton, negative = electron, and neutral = neutron
 Location of subatomic particles
 Nucleus = proton and neutron
 Electron cloud = energy levels containing electrons
Calculate numbers of protons, neutrons and electrons
 Electron configuration up through only 2-8-8 energy levels (the octet rule only applies to the
first three levels)
 Models of the atom
 Bohr model
 Limitations
o Electrons do not “orbit” the nucleus of an atom like planets orbit the Sun
o Scale does not represent the actual size of an atom or relative sizes/distances between
the particles
 Electron Cloud Model
Identify that protons determine an element's identity and valence electrons determine its
chemical properties, including reactivity
 Protons
 Increasing atomic number on the periodic table
 Determines identity of the element
 Valence electrons determine:
 Chemical properties such as reactivity.
 Elements in the same groups/family contain the same number of valence electrons
 Electron configuration up through only 3 energy levels
 In a NEUTRAL atom the number of protons and electrons are the same
Interpret the arrangement of the periodic table, including groups and periods, to explain how
properties are used to classify elements
 The periodic table is an arrangement of the known elements based on atomic number and
chemical properties
 Each element is represented by a chemical symbol, atomic number, and atomic mass
 The table is arranged into periods/rows and groups/families/columns
 Explain how properties are used to classify elements - relate to location on the periodic
table (metals, metalloids, nonmetals, noble gases)
 Chemical properties – reactivity relates to number of valence electrons and period;
identify locations of transition metals in the table, but do not introduce their chemical
behavior
 Physical properties –luster, conductivity, malleability, state of matter
 Elements in each period contains the same number of energy levels
Elements in the same groups/family contain the same number of valence electrons
Questions for Review:
1. Describe the structure of an atom, explaining the particles and where they are located:
2. Which subatomic particle determines the identity of an element?
3.
What is an element?
4.
Define the following:
Ion –
Anion –
Cation –
5.
Define the following:
Atomic number –
Elemental or chemical symbol –
Atomic mass –
6.
7.
If an element has a different number of neutrons, it is known as an _________________
List the three parts to the Particle Theory of Matter:
a.
b.
c.
8. What makes a chemical compound organic?
9. How are elements arranged on the periodic table?
10. List the descriptive properties of metals, nonmetals and metalloids:
Metals –
Nonmetals –
Metalloids –
Example Test Questions:
1. A student is studying calcium, a highly reactive element that humans need for strong
bones. Which characteristic of calcium is most closely related to its chemical reactivity?
a. The 20 protons in each atom of calcium
b. The density of calcium, which is 1.54 g/cm3
c. The atomic mass of calcium, which is 40.07 amu
d. The 2 valence electrons in each atom of calcium
2. A model of Beryllium is shown. What types of particles are found in the cloud surrounding the atom’s
nucleus?
a.
b.
c.
d.
Positively and negatively charged particles
Negatively charged particles only
Neutral and positively charged particles
Positively charged particles only
3. What is the mass number of a potassium (K) atom that has 20 neutrons?
a. 18
b. 19
c. 20
d. 39
4. Diagrams of atoms from four different elements are shown. Which two atoms are of
elements in the same group on the
periodic table?
a. Atom 1 and atom 2
b. Atom 1 and atom 4
c. Atom 2 and atom 3
d. Atom 3 and atom 4
Chemical Formulas and Reactions: *remember to review your test review from this Unit!
Recognize that chemical formulas are used to identify substances and determine the number of atoms of
each element in chemical formulas containing substances
 Substances have specific chemical formulas
 Examples:
 Water – H2O
 Carbon Dioxide – CO2
 Table Salt (Sodium Chloride) – NaCl
 Table Sugar (Sucrose) – C12H22O11
 Glucose – C6H12O6
Determine the number of atoms in each element in chemical formulas containing substances
 Process
 Name the elements present
 Count the total number of elements
 Count the number of atoms of each element
 Count the total number of atoms
 Key components of chemical formulas:
 Symbols
 Subscripts
 Coefficients
Ex: 2H2O = 6 atoms of 2 elements
Recognize whether a chemical equation containing coefficients is balanced or not and how that relates to the
law of conservation of mass:








Use equations to represent chemical reactions
Role of formulas to represent the substances in an equation
Subscript, coefficient, RAP – reactants, arrow (read as “yields”), products
Balanced equations represent the Law of Conservation of Mass
Determine whether a chemical equation is balanced or not
Formulas and equations express what happens in a chemical reaction
rearrangement of atoms, alteration of formulas between reactants and products
change in chemical formula/composition means it is a different substance with different
properties
Signs of chemical change – indicate you have a new substance that was not present before the
reaction or that an energy transformation occurred:
 Unexpected color change
 Release of gas
 Odor change
 Production of precipitate
 Sound
 Light (flame, bioluminescence, glow sticks, explosions)
 New chemical properties
 Change in temperature
Misconception Alert: Temperature change due to the addition or removal of heat does not
represent a chemical change - for example, melting or freezing is a change of state which is a
physical change.
Differentiate between elements and compounds [and mixtures] on the most basic level
 Element = pure substance
 Compound = pure substance made of two or more different elements joined together
 Examples: H2O, CO2, NaCl, C6H12O6 (carbohydrate)
 Mixture = 2 or more substances that are physically combined and retain the properties of their
substances
 mixtures of elements – brass is a mixture of copper and zinc (alloy)
 mixtures of elements and compounds – air
 mixtures of compounds – salt water, sand
 solution – a type of mixture in which the particles are evenly distributed
All organic compounds [carbohydrates, fats, proteins] contain the elements carbon and hydrogen. Most also
contain oxygen.
Example Test Questions:
1. The chemical formula for sodium sulfate is Na2SO4. How many sulfur atoms are in the
formula for sodium sulfate?
a. 1
b. 2
c. 6
d. 7
2. In the chemical reaction shown, the products are best classified as –
a.
b.
c.
d.
Two elements
One elements and one compound
Two compounds
Two compounds and one element
3. Four investigations that used 8 different liquids were done. In each investigation, the scientist
combined two of the liquids and recorded observations in the table. In which investigation is it least
likely that the liquids reacted chemically?
a.
b.
c.
d.
1
2
3
4
4. Based on its chemical formula, which of the following substances is an organic compound?
a.
b.
c.
d.
Urea, CH4N2O
Ammonium sulfide, (NH4)2S
Silane, SiH4
Sodium Chloride, NaCl
5. Which of these demonstrates the Law of Conservation of Matter by showing a balanced chemical
equation?
a. 2 Fe + 3 Cl2 −−→ 2 FeCl3
b. C4H10O + 6 O2 −−→ 3 CO2 + 5 H2O
c. C4H6O3 + H2O −−→ 4 C2H4O2
d. C7H16 + 11 O2 −−→ 5 CO2 + 8 H2O
Force and Motion:
Differentiate between speed, velocity, and acceleration:
 speed= distance/time
 velocity - speed and direction
 acceleration = change in velocity (speed or direction)
 Note: Misconception alert –students should understand that “acceleration” means it is a change in
speed or direction, not limited to speeding up.
 The term “deceleration” is not a scientific term for “negative acceleration in a specific direction” –
slowing down is acceleration
 graphic representations of speed, velocity and acceleration
Demonstrate and calculate how unbalanced forces change the speed or direction of an object’s motion:
 A force is a push or a pull. Forces act in a particular direction and are measured in Newtons. Forces occur in
pairs (acting with equal force on different “objects” in opposite directions). More than one force can act on
an object at a time. These forces can be either balanced or unbalanced.
 Determine net force and direction of net force
 Force = Mass x Acceleration; be able to manipulate this formula
Change of motion:




graphing change of motion
unbalanced forces do not always initiate motion, but cause changes in motion
balanced forces do not mean there is no motion, but that there is no change in the motion
Revisit the forces of gravity and friction. Know inertia and how it works.
Newton’s 3 laws state:
st
Newton’s 1 Law: Law of inertia
• Objects in motion stay in motion with a constant speed and direction unless acted on by an
unbalanced(net) force
• Objects at rest stay at rest unless acted on by an unbalanced(net) force
• Objects with more mass have more inertia
nd
 Newton’s 2 Law: Law of force and acceleration
• F=ma (students should understand this relationship both conceptually and
mathematically)
• The greater the force acting on an object, the greater the acceleration or change in motion of
that object (constant mass)
• The greater the mass of an object the less the acceleration when force is held constant
• The greater the mass of an object the greater the force needed to accelerate it to a given
acceleration
rd
 Newton’s 3 Law: Law of action-reaction/equal and opposite force pairs
• If a force acts upon an object, then an equal and opposite force must act upon the object that
exerts the force.
• For every force there is an equal force that acts in the opposite direction (force pairs)
• The equal and opposite force (reaction force) acts on the object that is exerting the original force
(action force) not on the object being acted on by the original force (action force).
• Example: A book resting on a table: The book exerts a force on the table downward; the table
exerts an equal force on the book upwards. The forces in the force pair are acting on two separate
objects.
Compare and contrast potential and kinetic energy:
 Potential energy- stored energy due to an object's position or condition
 Objects at rest, rocks on cliff, water at the top of a waterfall, car at the top of a roller coaster, stretched
rubber band
 Kinetic energy- is the energy an object has due to its motion

Objects in motion, rocks falling off a cliff or rolling down a hill, falling or flowing water, car moving on
track of a roller coaster, arrow flying through the air
Questions for Review:
1. What is potential energy? Give two examples of potential energy:
2. What is kinetic energy? Give two examples of kinetic energy:
3. What is a force?
4. What is the difference between balanced forces and unbalanced forces?
5. Draw a situation where the forces are balanced. Make sure your diagram is labeled.
6. Draw a situation where the forces are unbalanced. Make sure your diagram is labeled.
7. What is net force?
8. If my dog, Bella, is pulling a rope with a force of 80N to the left and my friend’s dog, Lucy,
is pulling on the opposite end with a force of 30N to the right, what is the net force of the
rope? What direction is the rope being pulled in?
80N
30N
9. Five different forces act on an object. Is it possible for the net force on the object to be zero?
Explain.
10. What three things can happen to an object when an unbalanced force acts on it?
11. What is Inertia? Give an example.
12. What is gravity?
13. How does friction affect an object’s motion?
14. Which forces would eventually cause a rolling ball to come to a stop?
15. A 250 kg trailer is being pulled by a truck. The force causes the trailer to accelerate at 4 m/s2. What is
the net force that causes this acceleration? Show your work-don’t forget units!
16. Hannah uses a force of 60 N to move a 30 kg bag of equipment. What is acceleration of the bag?
Show your work-don’t forget units!
17. Johnny’s balloon car travels a distance of 200 cm in 50 s. What is the balloon car’s speed? Show your
work-don’t forget units!
18. Mandy’s balloon car travels at a speed of 20 m/s for 10 s. What is the distance that the balloon car
traveled? Show your work-don’t forget units!
19. Define speed, velocity, and acceleration:
Speed –
Velocity –
Acceleration -
20. Create a graph that shows constant motion. Define constant speed:
Constant speed is:
21. Create a graph that shows an object at rest.
22. Create a graph that shows two runners running at a constant speed; one running slightly
faster than the other.
23. Create a graph that shows an object gradually speeding up
Example Test Questions:
1. A student uses a magnet to move a 0.025kg metal ball. The magnet exerts a force of 5 N,
which cases the ball to begin moving. What is the acceleration of the ball when it begins to
move?
a. 200 m/s2
b. 0.125 m/s2
c. 5 m/s2
d. 5.025 m/s2
2. When a space shuttle was launched, the astronauts onboard experienced an acceleration
of 29 m/s2. If one of the astronauts had a mass of 60 kg, what net force (in Newtons) did
the astronaut experience? _____________________
3. The graph shows distance over time.
Which of these situations could be represented by this graph?
a. A student walks 1.5 km to a friend’s house in 40 minutes. The two students then walk another 1.5
km to school in 20 minutes.
b. A student walks 1.5 km to a friend’s house in 20 minutes. The two students then walk another 1.5
km to school in 40 minutes.
c. A student walks 1.5 km to a friend’s house in 30 minutes. The two students then walk another 1.5
km to school in 30 minutes.
d. A student walks 1.5 km to a friend’s house in 20 minutes. The two students then walk another 1.5
km to school in 60 minutes.
4. Between which two locations would the greatest change in speed most likely occur?
a.
b.
c.
d.
Between T and U
Between U and X
Between T and X
Between S and T
5. Four students were asked to classify the activities of the people in the picture as examples of either
potential or kinetic energy.
Use the graph to answer questions 6 and 7:
6. Which swimmer maintained a constant speed during the race? (8.6B)
a. Mary and John both go the same speed
b. John
c. Mary
d. There is not enough information
7.
Which swimmer exhibited increased acceleration? (8.6B)
a. Mary
b. John
c. Neither accelerate during the race
d. There is not enough information
8. A book is sitting on a dashboard of a car that’s stopped at a traffic light. As the car starts to
move forward, the book slides off the dashboard. Pick the best response to explain why this
happens. (8.6C)
a. Gravity was stronger than the forward motion
b. The books mass was less than 200g
c. The book remains at rest and the car moves forward
d. Air resistance made the book move backward
9.
A student jumps off a sled toward the west after it stops at the bottom of an icy hill. Based on
the law of action-reaction, in what direction will the sled most likely move as the student
jumps off? (8.6C)
a.
b.
c.
d.
North
South
East
West
10. A book is sitting on a dashboard of a car that’s stopped at a traffic light. As
the car starts to move forward, the book slides off the dashboard. Pick the
best response to explain why this happens. (8.6C)
a.
b.
c.
d.
Gravity was stronger than the forward motion
The books mass was less than 200g
The book remains at rest and the car moves forward
Air resistance made the book move backward