8th Grade Benchmark Study Guide Answers
1. Measurement:
a. What is mass? The amount of matter in an object
b. What is volume? The amount of space an object occupies.
c. To measure the volume of a regularly shaped object use a rule and do L x W x H. To
measure the volume of an irregularly shaped object (like a rock) use a graduated
cylinder and measure the amount of water that is displaced when the object is dropped
in.
2. Matter:
a. The different phases of matter are Solid, Liquid, and Gas
b. What are the transformations from one phase to another called? See diagram below
c. What happens when energy is absorbed by the molecules? They warm up/speed up
d. What happens when energy is released from the molecules? They cool down/slow
down
e. How does water change when it is
transformed from a solid to a liquid?
H2O molecules move faster and are
farther apart. It is still H2O
f. How does water change when it is
transformed from a liquid to a gas?
H2O molecules move faster and are
farther apart. It is still H2O
3. Elements and Compounds
a. How are elements arranged on a periodic table? They are arranged in increasing atomic
number (number of protons) order. Why are they grouped in families? Each family of
elements has the same number of valence electrons and has similar chemical properties
and reactivity.
b. What are chemical changes? What are some examples?
Chemical changes are when the chemical structure of a
molecule is changed (H2O becomes 2H and O).
Examples occur when a chemical burns, rusts, cooks,
rots/molds, toasts, etc. It is usually not easily reversed.
c. What are physical changes? What are some examples?
Physical changes are when the substance changes phase
or shape, but the chemical formula remains the same.
H2O stays H2O, but now its ice or liquid or gas. Examples
include cutting, ripping, folding, bending, melting,
freezing, etc.
d. What are reactants and products for photosynthesis?
I-------------------reactants---------------------I I--------------products-------------------------I
4. Ecology
a. In a food web, how does energy flow through the web? Light energy from the sun flows
to the plants, which during the photosynthesis process; convert the light energy into
chemical (food) energy. The consumer will eat the producer (plant) and the chemical
energy will be turned into mechanical (movement) and heat energy. Which level of the
food web contains the most amount of energy? The plant (producer level) contains the
most amount of energy.
b. In a food web, how do the populations of one species affect the other species in the
food web? A large predator population can eat up all the prey population level. When
there is no prey left, the predator population levels will drop due to lack of food. What
happens if one is removed? The whole food web will change and be affected.
c. What are the three types of symbiotic relationships and how do they feel?
5. Atmosphere/Weather
a. What is conduction/convection/radiation?
b. What is air pressure and how does it change as you increase in altitude? The amount of
air molecules over an area. The air pressure decreases as you increase in altitude.
(fewer air molecules high on a mountain or high in a airplane.)
c. What is a front? How and where does it form? When two or more air masses (large
areas of air with similar temperature and humidity) come together, a front is formed.
These air masses often meet directly above the USA when the polar air masses from the
north collide with the tropical air masses from the south.
d. What are the four types of fronts and their symbols?
e. What are some examples of severe weather and where they can occur?
Blizzard- strong, long lasting snow storm with high winds. Usually form towards the
north and move southward during the winter
Thunderstorms- uplift of less dense, very humid air, condenses, forming cumulonimbus
clouds (rain clouds) As the water condenses, it forms rain. The swirling updrafts cause
the cloud to become electrically charged, producing lightning and thunder. They can
occur anywhere, but typically on the eastern US during the spring and summer seasons.
Tornadoes- when a large thunderstorm forms, a rotating column of wind can be tilted
until it touches the ground. Tornados will usually occur in Tornado Alley in the Central
US.
Hurricane- a low pressure storm over warm ocean water creates a large swirling center
of clouds that can build from a tropical storm to a hurricane. They form over the warm
ocean during the summer and fall months. Hurricanes lose power as they travel over
land.