Download Name______________KEY_________________ Grade 8 Science

Name______________KEY_________________
Grade 8 Science Midterm Review
I. Lab Safety
Review the lab safety procedures in your plastic sleeve.
II. Lab Equipment
Review the different types of equipment used throughout the year.
III. Minerals
1. a. Which two elements make up most of the Earth’s crust?
Oxygen
Silicon
b. Do elements in Earth's crust exist primarily as native (pure) elements or
compounds? Explain.
Most elements in Earth’s crust exist as compounds. Elements will react with
each other to increase their stability. When they react they form compounds.
2. List the five requirements for a substance to be considered a mineral.
1. Solid
2. Inorganic
3. Naturally occurring – made in nature
4. Atoms or molecules all have the same crystal structure
5. Same chemical composition throughout
3. Describe three ways minerals form.
1. evaporation – when water evaporates minerals are left behind.
2. heating/cooling – magma cools, elements and compounds group together to
form minerals
3. pressure – intense pressure breaks the bonds between compounds and the
atoms recombine to form new bonds and compounds
4. Give three examples of how minerals are useful. Explain how the properties of each
example make the mineral appropriate for its use(s).
Health – minerals such as calcium and phosphorus necessary to our diets
Industry – hard minerals like corundum can be used as abrasives (hardness)
Safety – halite used for deicing roads (lowers freezing point of water)
Technology – rare earth elements are important for tiny magnets in electronic
devices (magnetism), copper used for wires (conductive)
Jewelry – colorful minerals such as fluorite can be uses to make jewelry (color)
5. How are minerals divided into families?
Minerals are divided into families based on their composition.
6. Name three examples of mineral families.
1. Silicates
2. Oxides
3. Halides
7. What is the largest mineral family? Silicates
8. Which family reacts with acid? Carbonates
9. Take a deep breath.
10. Breathe out and continue working.
11. a. Diamond is the hardest mineral. This means that diamond is the most resistant to
scratching. Based on this property, how do you think diamonds are useful in industry?
Diamonds are used to make abrasives (to grind or scratch other substances),
drill bits and saw blades that can cut through other hard substances.
b. Diamond has a high luster and high light dispersion (prism effect), based on these
properties, what other use do humans have for diamond?
Diamonds can also be used to make jewelry due to how light interacts with them.
12. How do minerals get into our food? Describe both ways. Include what kind of food
obtains its minerals this way.
1. Some foods like some cereals and orange juice have extra or more minerals added.
2. Other foods, such as milk, have naturally occurring calcium that was in Earth’s
crust. Plants absorbed the calcium from soil as they grew. The plants were eaten by
cows and the calcium was incorporated in the milk that cows produce.
IV. Rocks
13. Label the arrows on the following diagram. Use the word bank below.
melting rock
lithification
heat and pressure
melting rock
lithification
heat and pressure
Sedimentary Rocks
heat and pressure
Igneous Rocks
Metamorphic Rocks
melting rock
14. Choose the letter of the rock type described by each statement.
I - igneous
S - sedimentary
__S__ a. form in layers collecting over time
M - metamorphic
__I__ b. form from magma or lava
__S__ c. formed from remains of plants + animals __S__ d. most likely to contain fossils
__S__ e. form from cementation and compaction
__I__ f. crystal size depends on the
rate of cooling
__M__ g. form from heat and pressure
__S__ h. form from pieces of rock
15. Compare igneous rocks formed by lava versus those formed by magma.
Cooling magma
Cooling lava
How/Where is it formed?
Crystal Size
Intrusive/formed below
large crystal size, coarse
ground, cools slowly
texture
Extrusive/Formed above
Small or no crystals, textures
ground, cools quickly or very
include: fine, glassy or
quickly
porous
16. Is there a relationship between an igneous rock’s origin and mineral content? Give an
example from the lab activity.
There is NOT a relationship between a rock’s origin and mineral content. Both
extrusive (above ground) rocks like basalt and intrusive (below ground) rocks like
gabbro can be mafic (low silica). Also, pumice and scoria are both extrusive (above
ground), however, pumice is felsic (high silica) and scoria is mafic (low silica).
17. Compare types of metamorphism.
Type of
What does the resulting rock
Where is this type of
Metamorphism
look like?
metamorphism likely to
occur?
Mostly Pressure
Foliated – minerals crystals
Regional - Mountain building
arranged in order, lined up
areas, areas where tectonic
plates meet
Mostly Heat
Non-foliated – mineral
Local – around magma
crystals random
18. Rock Uses
a. Give two examples of igneous rocks and their uses.
Obsidian used to make scalpels and arrowheads in the past, Granite used in
construction and countertops, Basalt used in jetties and railroad bases
b. Give two examples of sedimentary rocks and their uses.
Coal used as fuel to produce electricity, Geodes used in jewelry, Sandstone and
limestone use in monuments and construction
c. Give two examples of metamorphic rocks and their uses.
Marble used in statues and construction
Slate used in roofs and sidewalks
19. Which type of rock is most abundant? (both in U.S. and worldwide)
Sedimentary rocks are most abundant on the surface, while overall in the crust
igneous rocks are most abundant.
V. Groundwater
20. What is the difference between porosity and permeability?
Porosity is the capacity of a material to hold water – how much ‘empty’ space
there is in the material. Permeability is the ability of a material to allow water
to pass through it.
21. a. What factors contribute to the porosity of a substance?
Particle shape (rounded particles make more porous materials) and particle
sorting (same size particles make more porous and mixed size particles make
less porous)
b. What factors contribute to the permeability of a substance?
Larger pore size and more connected pores make a substance more permeable
22. What is an aquifer?
a geologic formation (soil or rock) below Earth’s surface that stores and or
transports water.
23. Would you want an aquifer to be more porous or more permeable or both? Explain.
Both. If an aquifer is more porous it can hold more water and if it’s more
permeable it allows water to flow through it more easily.
24. a. Explain what it means for a rock layer to be impermeable.
An impermeable rock layer does not allow water to pass through it.
b. What is the effect of an impermeable layer on the flow of groundwater?
An impermeable layer prevents water from flowing through it. It can prevent
recharge, add pressure or direct the movement of water through an aquifer.
c. What is another name for an impermeable layer? aquitard
25. a. What is a recharge area?
Surface region that allows water to flow downward into the earth and replenish
the aquifers.
b. What can happen if recharge does not occur?
If recharge doesn’t occur, the groundwater will not be replenished when used.
That could result in subsidence (sinking of the ground above it) and wells
running out of water to drink and for agriculture.
26. a. What is the diagram below called? contamination plume
b. The maximum contaminant level (MCL) is MEDIUM. What does that mean?
The MCL is the greatest amount of contaminant that is safe to drink. The area
shaded as ‘medium’ would, therefore, have the maximum amount of
contaminant allowed in parts and be unsafe to drink erring on the side of
caution.
c. Look at where there is a star (
). Is the water safe to drink there? Explain.
The water is currently safe to drink as it is below the MCL, however, it may
become unsafe in the future.
d. Circle the source of contamination.
e. The fact that you can single out one source of contamination means this is an example
of
point source
or
non-point source
(circle one)
All topics and labs covered since the beginning of second quarter
may be included on this exam. Please review all labs and notes
that you have completed since the beginning of Quarter 2. Your
textbook is also a great resource. The exam is worth 2 times a
regular test. It can really impact your grade. Be sure to bring at
least 2 pencils with good erasers.