8thGr Benchmark

Many people use the word theory to mean a guess or an idea. What do scientists mean when they use the word theory?

• an explanation that has a great deal of evidence to support it

• one of several possible ideas a scientists has about what causes a natural event to occur

• a possible explanation to a scientific question

• a hypothesis that has been supported by at least one experiment

Which of the following is always involved in a scientific inquiry?

• knowing the correct answer before you start

• coming up with questions based on observation and reasoning

• guessing what would happen instead of doing experiments

• conducting surveys to ask people's opinions on various subjects

Mary thought that the number of frogs in the neighborhood pond had decreased over the last few years. So, she decided to count the number of frogs she saw around the pond twice each day for ten days. Mary's data is displayed in the table below.

Based on her observations, which of the following can Mary infer?

• frogs are consumed by predators in the morning and are reborn in the evening

• the number of frogs at the pond has steadily increased over the last 2 years

• frogs rest during the afternoon and become more active in the evening

• the number of frogs at the pond has steadily declined over the last 2 years

Sunspots are dark areas on the surface of the sun. They mark strong magnetic fields, and more sunspots indicate that the sun is more acting and is releasing more energy. The following graph presents the average daily number of sunspots from 1900 through 1944. Each data point is the average for one month.

Notice the series of peaks and troughs in the graph. The time from one minimum (trough) to the next is called a Solar Cycle. Solar Cycles can be anywhere from 9 to 14 years long.

What can be predicted with the most certainty from this graph?

• the average daily number of sunspots in 1949 will be 80.

• the average daily number of sunspots will peak in 1949

• the next minimum in the graph will be in 1953

• the average daily number of sunspots will increase throughout 1945

Today, air travel allows large numbers of people to move quickly over long distances. Which of the following is a likely effect of air travel technology?

• News will travel more slowly from one place to another

• Cultures will become more distinct from each other

• International trade will become less common

• Diseases will be spread more quickly

Farmers often must add fertilizer to soil that is deficient in nutrients. Which statement best describes an effect that this might have?

• The fertilizer could runoff and pollute nearby water sources

• The fertilizer could cause crops to release pollution into the air

• The fertilizer could kill useful insects

• The fertilizer could make the soil too fertile to grow crops

Frances' classroom faces west. When the sunlight comes in through the windows, it gets very warm in the classroom.

Which scientific principles will be most helpful to Frances in designing a solution to this problem?

• electromagnetic attraction and repulsion

• conservation of total mechanical energy

• transformation of mechanical energy

• absorption and reflection of light waves

Suppose a bicycle was coasting on a surface, and there was no friction. What would happen to the bicycle's speed?

• the speed would remain constant

• the speed would decrease but you would never stop

• the speed would increase since there is no friction

• the speed would decrease until you finally came to a stop

Ten years ago, the ratio of birds to snakes in a local desert ecosystem was 2:5. Over the last 10 years, disease and hunting by humans has cut the bird population in half. The snake population has not changed. What is the current ratio of birds to snakes in this local ecosystem?

• 2:2.5

• 2:5

• 1:5

• 1:2

Look at the following example of technology:

How can this form of technology most likely improve a person's life?

• Using this technology takes less physical exertion than driving a car

• This technology can help a person travel very long distances

• Using this technology instead of the automobile helps improve air quality

• This technology can improve a person's math skills