1. Which of these is the best description of a galaxy?

A a collection of about twenty starsB a collection of a few hundred of starsC a collection of several thousand starsD a collection of many billions of stars

2. Which of these substances in living things is made up of

very large molecules? A air B fat C salt D water

3. Which of these elements is most commonly found in

molecules of living organisms?

A calcium B carbon C iodine D iron

4. Ashley wants to test her hypothesis that protein molecules are the largest molecules found in living organisms. She will use a series of membranes, each of which allows molecules of a different size to pass through.

A collect cells that contain the molecules to be testedB try to pass protein molecules through all the membranesC try to pass water molecules through all the membranesD explain why protein molecules are the largest moleules

known

5. Which of the following statements about gravity is true?

A Because of gravitational forces, stars are never perfect spheres

B The moons of Jupiter would crash into each other without gravity

C Gravitational force is necessary for the creation of stars and galaxies

D Gravity causes all objects in the universe to move away from one another

6. John hiked 20 km, drove 500 km in his car, and traveled 200 km by boat. Each activity took 5 hours to complete.What is John’s average speed for the entire trip?

• 48km/h

7. The table below shows the results of a student investigation that included identical ramps and identical marbles. Each student rolled a marble down a ramp and measured the distance it rolled. Which of the following variables may have affected the results of this investigation?

A Dave pushed the marble instead of just letting it goB Dave’s marble was less smooth than the other marblesC Dave’s marble was affected by a different gravitational forceD Dave started the marble lower on the ramp than the other students did

Student Distance Marble Traveled

Joe 2.6 mLucy 2.9 mDave 4.2 mLeona 2.7 m

8. What is the direction and size of the buoyant force acting on a cork floating in water?

A upward and equal to the weight of the water displaced by the cork

B downward and equal to the weight of the water displaced by the cork

C upward and equal to the weight of the amount of cork below the surface of the water

D downward and equal to the weight of the amount of cork below the surface of the water

9. Scientists want to find the density of a 25-gram rock. The diagram shows what happens to the water level in a 10-milliliter graduated cylinder after the rock is put into it.

What is the density of the rock sample?