8th Science Semester 1 Review

Immediately after a forest fire, the primary consumers in the area will compete most for which biotic factor?

• Food

• Space

• Oxygen

• Sunlight

Students mixed two liquids in a beaker and listed their observations. Based on these observations, which statement contains the best evidence that a chemical reaction occurred?

• There is a change in shape.

• There is a change in volume.

• The two liquids mix into a solution.

• The two liquids form a new substance.

Which pair of elements are nonmetals and gases at room temperature and normal atmospheric pressure?

• Fluorine (F) and Chlorine (Cl)

• Boron (B) and Aluminum (Al)

• Hydrogen (H) and Cesium (Cs)

• Cobalt (Co) and Nickel (Ni)

A farmer digs a small pond in a pasture. The farmer adds young individuals from two species of algae-eating fish to the pond and plants some reeds around the edges of the pond. The farmer wants the pond to be a sustainable ecosystem.

Which of the following would be most helpful in increasing the pond ecosystem’s sustainability?

• Decreasing the number of plant species around the edges of the pond

• Introducing older fish of the same species into the population of algae-eating fish

• Having a greater diversity of living organisms in the pond

• Adding gravel between the water and where the reeds are planted

How many neutrons are in the nucleus of a potassium atom with a mass number of 39?

The names and chemical formulas of four substances are shown in the chart. Which substance listed in the chart is made up of the most atoms?

• Carbonic acid

• Nitric acid

• Phosphoric acid

• Sulfuric acid

The temperature of a star determines the wavelength of visible light that is produced. The visible part of the electromagnetic spectrum is shown. Stars with the highest temperatures will emit most of their light at wavelengths that are near —

• blue light

• green light

• orange light

• red light

Students create a table that lists processes observed in nature. Which process describes only a physical change?

• process 1

• process 2

• process 3

• process 4

The Hertzsprung-Russell diagram shown is divided into four sections. Which section of the diagram includes the coolest, brightest stars?

• section 1

• section 2

• section 3

• section 4

How do you find the atomic number?

• by the number of electrons

• by the number of protons

• by the number of neutrons