WorksheetsScience Review for 8th Grade - 2/3/26
Total questions: 40
Worksheet time: 20mins
A piece of metal is composed of atoms. Each atom in the metal contains 29 protons. How is the metal classified?
compound
element
mixture
solution
Why is calcium in group 2, period 4 on the periodic table?
Calcium, like all group 2 elements, is nonreactive and a gas at room temperature
Calcium, like all period 4 elements, is nonreactive and a gas at room temperature
Calcium, like all group 2 elements, is reactive and a solid at room temperature
Calcium, like all period 4 elements, is reactive and a solid at room temperature
A copper wire was cut into pieces and dropped into a test tube containing acid. Bubbles formed immediately, the liquid in the test tube turned green, and the pieces of wire were no longer visible. Which most likely happened to the pieces of the copper wire?
The copper wire was chemically changed when it was cut and placed int he acid.
The copper wire was physically changed when it was cut and placed in the acid.
The copper wire was physically changed when it was cut and chemically changed when it was placed in the acid.
The copper wire was chemically changed when it was cut and physically changed when it was placed in the acid.
The balanced equation below represents a chemical reaction.
FeS + 2HCl → FeCl2 + H2S
According to the law of conservation of mass, how many hydrogen and chlorine atoms are required for this reaction?
1 hydrogen atom and 1 chlorine atom
1 hydrogen atom and 2 chlorine atoms
2 hydrogen atoms and 1 chlorine atom
2 hydrogen atoms and 2 chlorine atoms
To ensure renewable energy resources, government regulations require logging companies to replant trees after they clear-cut a forest. Why is clear-cutting still a concern for the environment?
It destroys entire habitats.
It usually kills all animal life.
It can cause acid rain to form.
It usually causes the extinction of most plant life.
What will most likely occur if communities around the world increase the amount of wood they burn for heat?
CO2 in the atmosphere will increase.
CO2 in the atmosphere will decrease.
Dissolved oxygen in the water will increase.
Dissolved oxygen in the water will decrease.
A scientist pours two liquids into a flask and swirls the flask to combine the liquids. The scientist then places the flask on a laboratory workbench. After a few seconds, the liquids separate into layers. How are the contents of the flask classified?
element
compound
homogeneous mixture
heterogeneous mixture
What elements have similar chemical properties?
Na, K, Mg
B, Al, S
N, O, F
He, Ar, Kr
What distinguishes chemical changes form physical changes?
Physical changes are permanent, while chemical changes are temporary.
Chemical changes produce new substances, while physical changes do not.
Physical changes alter the properties of the substance, while chemical changes maintain the same properties.
Chemical changes result in the change in mass, while physical changes do not.
Two reactants, X and Y, are combined and form a new substance with a mass of 375 grams. The mass of reactant X is 300 grams. What is the mass of reactant Y?
75 grams
175 grams
675 grams
975 grams
What is a possible disadvantage of using a hydroelectric dam as a source of energy?
Hydroelectric dams can harm the aquatic ecosystems both above and below the dam.
Hydroelectric dams can harm the atmosphere by producing toxic gas.
Hydroelectric dams do not produce carbon dioxide emissions.
Hydroelectric dams do not produce radioactive waste.
What is one way to reduce the use of nonrenewable energy resources?
building additional gas-powered factories in rural areas
making more efficient gas-powered automobiles
burning coal instead of wood in a fireplace
mining for coal instead of drilling for oil
A solid powder is composed of molecules containing silver, nitrogen, and oxygen atoms. All of the molecules are identical. How is this substance classified?
heterogeneous mixture
homogeneous mixture
compound
element
Which atom as 12 protons?
carbon
nitrogen
sodium
magnesium
A student lights the widk of a candle, and the candle burns for several minutes. The student makes the following observations:
- Observation 1: The white candle wick turns black as it burns
- Observation 2: The solid candle wax near the flame transforms into a liquid
Which choice best compares these two observations?
Observation 1 describes a physical change, and Observation 2 describes a chemical change.
Observation 1 describes a chemical change, and Observation 2 describes a physical change.
Each observation describes a physical change.
Each observation describes a chemical change.
The reactants for a chemical reaction are below:
CH4 + 2O2 → CO2 + 2H2O
If there is one carbon atom at the beginning of the reaction, how many carbon atoms should be present at the end of the reaction?
0
1
2
3
A company discovers a coal reserve under a mountain. The company uses bulldozers to remove soil and flatten the top of the mountain to expose the bedrock. Then, the company uses machines to remove coal from the exposed bedrock. How will obtaining the coal affect the environment?
The removal of soil will increase the rate of erosion, and the removal of coal from the mountain will decrease the volume of carbon dioxide in the atmosphere.
The removal of soil will decrease the rate of erosion, and the removal of coal from the mountain will decrease the volume of carbon dioxide in the atmosphere.
The removal of soil will increase the rate of erosion, and the flattening of the mountain will change the direction in which water flows off the mountain.
The removal of soil will decrease the rate of erosion, and the flattening of the mountain will change the direction in which water flows off the mountain.
A scientist tests a water sample that was collected from a river. The results of the test are described below:
- The water is clear
- The water contains dissolved calcium
How should this water sample be classified?
element
compound
homogeneous mixture
heterogeneous mixture
A hydroelectric dam produces all of the electricity for a community. The hydroelectric dam's reservoir is refilled by a river. Suppose the watershed that feeds the river experiences years of severe drought. How would the drought affect the electricity produced by the hydroelectric dam?
The drought will increase the dam's ability to produce electricity, because the water in the reservoir will have more potential energy.
The drought will have no effect the dam's ability to produce electricity, because hydroelectric dams transfer energy from aquifers.
The drought will have no effect on the hydroelectric dam, because there will still e water downstream of the dam.
The drought will reduce the dam's ability to produce electricity, because the reservoir will refill at a much slower rate.
Which will occur if humans continue to overload water systems with excess nutrients?
chemo-synthesis
eutrophication
nitrification
photosynthesis
Which groundwater contaminant contained in fertilizers and pesticides comes from farms?
bacteria
mercury
nitrates
sodium
Which is most likely to happen when river water temperature rises above 35 degrees Celsius?
The water will become polluted.
The dissolved oxygen levels will increase.
There will be negative health effects on wildlife.
There will be decreased evaporation from the river.
Which best explains why water quality standards have been created to ensure heavy metals in water are kept to a minimum?
Heavy metals are linked to toxicities in humans and large amounts of heavy metals should not be consumed.
Heavy metals can stain ceramic surfaces in homes and cost the homeowners hundreds in repairs.
Heavy metals can cause discoloration of water and can cause a strong unpleasant odor.
Heavy metals can corrode pipes and cause problems with internal plumbing.
Which best explains a way of protecting water for human consumption?
Ban the use of lakes and rivers for recreation
Allow dumping of some wast into lakes and rivers
Reduce the use on lakes and rivers for irrigation of crops
Improve water quality standards for industries located on lakes and rivers
The Environmental Protection Agency was assigned which task?
setting standards and governing the cleanliness of water used by Americans
setting standards and governing the highways and interstates in the United States
setting standards and governing the use of national parks and monuments in the United Sates
setting standards and governing the civil and commercial air transportation throughout America
What step in the water treatment process involves the removal of suspended particles?
aeration
desalination
disinfection
filtration
Cholera is a bacterial disease that is spread throughout a community by contaminated water. How can the spread of cholera be prevented?
by giving healthy people antibiotics before they get sick
by hand washing with contaminated water before food preparation
by using chlorine to treat sewage before it enters the water supply
by using waste to fertilize fields instead of releasing it into the water supply
Which steps in the water-treatment process use positively charged chemicals to balance negatively charged sediment, leading to the formation of larger particles when these oppositely charged particles combine?
sedimentation and coagulation
disinfection and sedimentation
coagulation and flocculation
disinfection and flocculation
Which is a most likely example of point source pollution?
fertilizer sprayed onto a field
water runoff from a city street
a pipe flowing into a river
motor oil from the road washing into the ditch
Which is a compound?
sodium
sugar
nitrogen
air
Which best describes a method of obtaining energy that may cause changes in water temperature and harm to fish populations?
burning coal
using ethanol in cars
installing solar panels on a home
generating electricity in a hydroelectric power plant
Which would indicate the water in a lake is not safe for drinking?
many varieties of fish in the lake
high dissolved-oxygen levels in the lake
cold water temperature of the lake
high turbidity levels in the lake
In some environments, wolves prey on deer for their source of food. If all of the wolves were taken from the environment, what would most likely happen to the deer population?
The deer population would increase and begin to compete for food.
The deer population would become larger and healthier animals.
The deer population would decrease, because there would be an increase in disease.
The deer population would change color, because they would not have to hide from wolves.
How are mutualism and parasitism different?
Both organisms benefit in mutualism, while in parasitism only one organism benefits at the other's expense.
Both organisms benefit in parasitism, while in mutualism only one organism benefits at the other's expense.
Both organisms benefit in mutualism, while in parasitism one organism benefits, and the other is neither harmed nor benefits.
Both organisms benefit in parasitism, while in mutualism one organism benefits, and the other is neither harmed nor benefits.
What would have the greatest long-term impact on reducing the amount of carbon dioxide in the air?
planting trees around a farm
cutting down trees around a farm
increasing the number of livestock on a farm
decreasing the number of livestock on a farm
Which is the primary source of energy for most cells in the body?
sugar
fat
protein
vitamin
Which is classified as an element?
carbon dioxide
iron
vinegar
water
What happens to most of the energy as it moves throughout a food web?
It is changed into light energy
It is changed into heat energy
It is changed into mass
It is changed into decomposers
Where do plants get the food they need for energy?
They absorb it directly from the sun
They absorb it directly from the soil
They produce it during photosynthesis
They receive it from atmospheric gases
What effect does the water cycle have on the total amount of water on Earth?
The total amount of water on Earth is constantly increasing.
The total amount of water on Earth is constantly decreasing.
The total amount of water on Earth remains relativel constant.
The total amount of water on Earth changes due to periods of global warming and cooling.
