6th-8th Grade Practice 2

According to the graph, which air pollutant decreased the most from 1970 to 1991?

• Carbon monoxide

• Sulfur oxides

• Particulates

• Lead

Insulation materials reduce heat loss because they -

• are poor conductors

• block out the sun

• reduce evaporation

• promote convection

Which process is a physical change?

• Rusting iron

• Burning coal

• Tarnishing silver

• Melting ice

What process makes food for plants?

• Reproduction

• Photosynthesis

• Respiration

• Condensation

"Hypothesis: The addition of fertilizer to soil will increase plant growth."

Which of these experimental designs would best test this hypothesis?

• 
• 
• 
• 

Fossil fuels such as gas, oil, and coal have what kind of energy?

• Mechanical energy

• Chemical energy

• Electrical energy

• Nuclear energy

After fishing in the ocean, a student left his fishing gear in the sun to dry. Later, he noticed that small white crystals had formed on the rod, reel, and fishing line. Which of these is the best explanation of what occurred?

• The water evaporated from the fishing gear, and sand was attracted to it.

• The fish that were caught left scales on the fishing gear.

• The salt in the ocean water reacted with the fishing gear and caused it to rust.

• The water evaporated from the fishing gear, and salt from the ocean was left behind.

Which of these would be the best way to prove that a pine stick is more flexible than an oak stick?

• 
• 
• 
• 

Which of the following is a true statement about the magnetic field between two magnets?

• The south pole of one magnet is attracted to the south pole of the other magnet.

• The south pole of one magnet is attracted to the north pole of the other magnet.

• The north pole of one magnet is attracted to the north pole of the other magnet.

• The south pole of one magnet is attracted to both poles of the other magnet.

In the chemical formula for ammonia, NH₃, what does the subscript 3 represent?

• The number of nitrogen and hydrogen atoms in each molecule of ammonia.

• The number of hydrogen atoms in each molecule of ammonia.

• The number of ammonia molecules that will bond together.

• The number of nitrogen atoms in each molecule of ammonia.