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8th Grade Benchmark Study Guide Answers
1.
a.
b.
c.
Measurement:
What is volume? The amount of space an object occupies measured in mL or gm/cm3
What is mass? The amount of matter in an object measured in grams, milligrams, etc
To measure the volume of a regularly shaped object use a ruler 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. What is an element? A substance that cannot be broken down into simpler substances
It contains only one kind of atom
b. What is a compound? Pure substance composed of two or more
different elements joined by chemical bonds.
c. What is a molecule? A molecule is a group of atoms joined
together.
It is the smallest part of an element or compound that can exist independently.
d. 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.
e. Are new substances made in a chemical change? YES
f. Does the total mass of the substances change after a reaction? No, the
mass remains the same
g. 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.
h. Are new substances/molecules made in a physical change? NO
i. Is a phase change a physical or chemical reaction? Physical Does the molecule change its chemical
structure? NO
j. Where are the metals located on a periodic table and what are their characteristics?
Metals are located to the left and below the diagonal line in the periodic table. Metals are usually solids
at room temperature. Metals are good conductors of heat and electricity
What are reactants and products for photosynthesis?
I-------------------reactants---------------------I I--------------products-------------------------I
Atmosphere/Weather:
a. What is conduction/convection/radiation? Sketch an example of each and explain
b. What are the layers of the atmosphere?
A
Troposphere
B
Stratosphere
C
Mesosphere
D
Thermosphere
E
Exosphere
c. How are UV rays dangerous and what protects us from them?
The atmosphere protects us from Ultraviolet rays, specifically the ozone
layers. The ultraviolet rays are harmful and can cause skin cancer
5. Energy and Motion:
a. What is a force? A force is a push or a pull
b. How does a force affect the motion of an object? A force can cause an object to move
c. What is Newton’s first Law of Motion?
Newton’s first law of motion states that an object at rest will remain at rest or an object in motion
will remain in motion until a force acts on it
d. What is energy, what do we use it for? Energy is the ability to do work or cause change. We need
energy to live.
Forms of energy- Be able to describe each form and identify examples of each
1. Potential Potential Energy is stored energy. Examples of potential energy are oil sitting in a
barrel, or water in a lake in the mountains.
2. Kinetic energy Kinetic Energy is energy that is in motion. Moving water and wind are good
examples of kinetic energy.
3. Mechanical energy Mechanical Energy is the energy of motion that does the work. An
example of mechanical energy is the wind as it turns a windmill.
4. Thermal energy energy that is pushed into motion by using heat
5. Sound energy Sound is produced when a force causes an object or substance to vibrate- the
energy is transferred through the substance in a wave.
6. Chemical energy Chemical Energy is energy caused by chemical reactions. A good example
of chemical energy is food when it is cooked.
7. Electromagnetic/Light energy Electrical Energy is when electricity creates motion, light or
heat. An example of electrical energy is the electric coils on your stove.
8. Nuclear energy The energy that holds protons and neutrons together in the nucleus of an
atom
e. How can you change the amount of potential and kinetic energy of an object? (think of the marble
and roller coaster labs)
The amount of potential and kinetic energy of an object can be changed by adjusting the mass,
height and speed of the object. Objects with more mass have greater potential energy The formula
to find P.E. is P.E. = Weight X Height.
The faster an object moves, the more kinetic energy it has.
The greater the mass of a moving object, the more kinetic energy it has.
Kinetic energy depends on both mass and speed.
f. Describe how heat energy will flow in the following diagrams
From the spoon to your hand
From your hand to the ice cube
Why does the heat energy travel this way? Heat will always travel form hotter area to a colder area
How can you prevent the transfer of heat along the spoon? You can use an insulator to slow the
transfer of heat. Metal is a good conductor of heat but an insulator will slow the transfer of heat