STAAR Science Grade 8

1.Two gold samples are tested. Every atom in the first sample has 79 protons and 118 neutrons. Every atom in the second has 79 protons and 116 neutrons. Why are both samples gold?

2.Every atom in gas sample A has 8 protons. Every atom in gas sample B also has 8 protons, but some of those atoms have extra neutrons. What can you conclude?

3.A model of a nitrogen atom has 7 proton beads in the nucleus. A student adds one proton bead. Which element does the model show now?

4.A diagram of an atom shows a tiny dense center and a much larger region around it. Where are the electrons found?

5.A poster says the nucleus contains protons, neutrons, and electrons. Which correction should be made?

6.Wood contains carbon-12 atoms, with 6 protons and 6 neutrons, and carbon-14 atoms, with 6 protons and 8 neutrons. What are carbon-12 and carbon-14?

7.A table lists atom P with 17 protons and 18 neutrons, atom Q with 17 protons and 20 neutrons, and atom R with 18 protons and 18 neutrons. Which statement is correct?

8.A neutral aluminum atom has atomic number 13. Which count is correct for that atom?

9.One atom in a compound has 12 protons and 10 electrons. A student says it is no longer magnesium. What is the best correction?

10.A card for a neutral fluorine-19 atom lists atomic number 9 and mass number 19. How many neutrons does that atom have?

11.A student finds the mass number of a neutral atom by adding 11 protons and 11 electrons, getting 22. Why is that method wrong?

12.Atoms in a sodium lamp have 11 protons and 12 neutrons. What are the atomic number and the mass number?

13.A copper wire is bent into a hook. The hook still conducts electricity and is still copper. What kind of change is bending the wire?

14.An iron bicycle chain left in the rain develops a reddish brown coating. The coating does not turn back into shiny iron when it is dried. What happened?

15.In one kitchen, butter melts in a warm pan. In another, bread turns black and smoky when it burns. Which statement is correct?

16.Water boils in a kettle, and steam leaves the spout. A student says a new substance formed because a gas appeared. What is the best correction?

17.A sealed bottle holds 16 g of liquid. A 9 g tablet is added, and the bottle is sealed again before the tablet reacts and a gas appears inside. What is the mass of the materials inside after the reaction?

18.Inside a closed jar, materials with a total mass of 15 g react. The solid product has a mass of 9 g, and the rest is a gas trapped in the jar. What is the mass of the gas?

19.The equation 2 H2 + O2 -> 2 H2O is written on the board. How many hydrogen atoms are on the reactant side?

20.Which equation has the same number of each kind of atom on both sides?

21.A notebook shows N2 + 3 H2 -> 2 NH3. How many nitrogen atoms are on the product side, and is the equation balanced?

22.Students start an atom table for 2 Mg + O2 -> 2 MgO. The reactant side shows 2 magnesium atoms and 2 oxygen atoms. The product side shows 2 magnesium atoms. How many oxygen atoms are on the product side?

23.A copper wire conducts electricity and bends without breaking. A lump of sulfur does not conduct and crumbles when it is hit. Which classification fits these results?

24.A student says charcoal must be a metal because carbon is solid at room temperature. The charcoal is dull, brittle, and a poor conductor. What is the best correction?

25.Lithium and potassium are in the same column of the periodic table. Lithium has 3 protons, and potassium has 19. Which statement is correct?

26.Chlorine and argon sit side by side in the same row of the periodic table. Chlorine is a reactive nonmetal gas. Argon rarely forms compounds. What does this show?

27.Element Z is placed in the same group as sodium and potassium. Which property is the best prediction for element Z?

28.Helium and neon are in the same group. Which property do they share?

29.A cyclist travels 180 meters along a park path in 30 seconds. What is the cyclist's speed?

30.A freight train travels 420 kilometers in 6 hours at a steady rate. What is its speed?

31.A student walks 54 meters down a hallway in 18 seconds. What is the walking speed?

32.Remote-control car A travels 72 meters in 8 seconds. Car B travels 40 meters in 5 seconds. Which car is faster, and what is that car's speed?

33.A delivery drone flies at a constant 15 m/s for 6 seconds. How far does it travel in that time?

34.A skateboarder moves at a constant 5 m/s toward a cone that is 65 meters away. How long does it take to reach the cone?

35.A ball rolls in a straight line. It is at 10 meters after 2 seconds, 20 meters after 4 seconds, and 30 meters after 6 seconds. What is its speed?

36.A bus travels 100 meters in 10 seconds, then travels 20 meters in the next 30 seconds. What is the average speed for the whole trip?

37.Two teams pull a rope in opposite directions with 80 N each. The flag in the middle stays still. What is the net force on the flag?

38.A child pushes a wagon east with 35 N. Friction pushes the wagon west with 15 N. These are the only horizontal forces. What is the net force?

39.A car on a straight highway uses cruise control and keeps a constant velocity. A passenger says a forward net force is required to keep it moving. What is correct?

40.The net force on an object is zero. Which statement must be true?

41.A soccer ball is rolling straight across the grass. A player kicks it from the side, and the ball's path bends. What does the kick show?

42.A city bus brakes suddenly. A standing rider, who is not holding a rail, keeps moving forward relative to the bus. Why?

43.The same push is used on an empty shopping cart and on a cart loaded with water jugs. The loaded cart speeds up less. Why?

44.A space probe is far from any planet, with its engines off. It moves in a straight line at a steady speed. Why does it keep moving?

45.A crate has a mass of 4 kg. The net force on it is 20 N. What is its acceleration?

46.A 6 kg box accelerates at 3 m/s^2 in a straight line. What net force is acting on the box?

47.A cart accelerates at 4 m/s^2 when the net force on it is 16 N. What is the mass of the cart?

48.A net force of 12 N is applied, in separate trials, to a 3 kg cart and to a 6 kg cart. What are the accelerations?

49.A wagon has a mass of 5 kg. A 10 N net force gives it one acceleration. The net force is then changed to 20 N. What are the two accelerations, in order?

50.An ice skater pushes on a rink wall and then moves away from the wall. Which force pair explains the motion?

51.A model rocket lifts off. The engine sends exhaust gases downward. Which statement describes the force pair?

52.Two students on skateboards push on each other with a force of 80 N. Each student has a mass of 40 kg. One says the pushes cancel, so neither person should move. What happens?

53.A book is slid across a carpet. It slows down and stops. Which force explains the slowing?

54.A student pushes a 6 kg bin forward with 24 N. Friction pushes backward with 6 N. These are the only horizontal forces. What is the bin's acceleration?

55.In a chamber with the air removed, a hammer and a feather are released from the same height at the same time. What happens?

56.A class uses 10 N of gravitational force for each kilogram. Air resistance is small enough to ignore. A 4 kg rock and a 1 kg rock are dropped. Which statement is correct?

57.A class spins a globe once while a lamp stays still. The spin models one rotation of Earth. About how long is one rotation, and what does it cause?

58.A poster says Earth's trip around the Sun causes day and night. What is the error?

59.Earth completes one full revolution around the Sun. About how long does that take, and what is that time called?

60.At the same moment, it is noon in one city and midnight in a city on the opposite side of Earth. Why?

61.In June, the Northern Hemisphere tilts toward the Sun. What does that tilt cause in the Northern Hemisphere?

62.A data card says Earth is closest to the Sun in early January. A student in Texas says January must be summer there because Earth is closer. Which correction is best?

63.On December 21, the Southern Hemisphere tilts toward the Sun. Which statement matches that date?

64.Equal areas of ground receive sunlight. Near the equator the light comes from overhead. Near a pole the light arrives at a slant. Which area gets more concentrated energy?

65.The Sun lights half of the Moon all month. From Earth, the Moon looks dark, partly lit, or fully lit on different nights. What are those changing views?

66.On a clear night the whole face of the Moon looks bright. The Moon is opposite the Sun in the sky. Which phase is this, and why does it look bright?

67.During a new moon, the Moon is roughly between Earth and the Sun, but not lined up for an eclipse. Why does the Moon look dark?

68.A student says the Moon's monthly phases happen because Earth's shadow moves across the Moon. Which response is accurate?

69.About a week after the new moon, half of the Moon's face looks lit. What phase is that?

70.Two nights after a new moon, a thin bright edge of the Moon is visible. Over the next several nights that bright part grows. What phase is the thin edge?

71.People in a narrow path see the Sun blocked in the daytime, and the sky darkens for a short time. The Moon's shadow falls on Earth. What is the lineup?

72.The full moon darkens for a while as it passes through a shadow. Earth is directly between the Sun and the Moon. What is happening?

73.Which order of the Sun, Earth, and Moon is a lunar eclipse?

74.The Moon is roughly between Earth and the Sun at every new moon. Why is there not a solar eclipse every month?

75.Which statement about the Sun is correct?

76.Venus looks very bright in the evening sky. A student calls Venus a star. What is the best correction?

77.A plate moves 4 centimeters per year. How far does that plate move in 25 years?

78.At a mid-ocean ridge, two plates move apart, and melted rock rises to form new seafloor. What kind of plate boundary is this?

79.Along a coast, an oceanic plate moves toward a continental plate and sinks beneath it. A deep trench forms. What kind of boundary is this?

80.A world map shows most earthquakes clustered in long belts. Those belts match the edges of tectonic plates. What does the pattern show?

81.Water seeps into a crack in a cliff, freezes, and splits the rock. The pieces are still at the base of the same cliff. What process broke the rock?

82.After a cliff rock breaks, a stream carries the pieces down the valley. Which statement names the processes correctly?

83.Prairie grass uses sunlight to make food. It does not eat other organisms. What role does the grass have in the ecosystem?

84.A coyote eats prairie dogs. It cannot make food from sunlight. What is the coyote in this food chain?

85.Bracket fungi grow on a dead mesquite branch and break the wood down into simpler materials. What is the role of the fungi?

86.A food chain is bluestem grass, then a cricket, then a lizard, then a hawk. Which organism is the producer?

87.In a pond food web, an arrow points from algae to a minnow. The minnow eats the algae. What does the arrow mean?

88.A heron eats fish. A student draws the food-web arrow from the heron to the fish and says the arrow should point to whatever gets eaten. What should the arrow show?

89.Plants in a meadow store 40,000 kJ of energy. About how much of that energy is stored in the animals that eat those plants?

90.Plants in a marsh store 7,000 kcal. About how much energy is stored two steps later, in animals that eat the animals that eat the plants?

91.Only about 10 percent of the energy in one level of a food chain is stored in the next level. Where does most of the rest go?

92.A pond study lists largemouth bass, cattails, and bacteria. How should these three be classified?

93.The same pond study lists water temperature, sunlight, and dissolved salts. How should these three be classified?

94.A fallen oak log lies next to a granite boulder. The log came from a tree that died last year. Which statement is correct?

95.A field has enough food and space to support about 30 rabbits for many years. The population is 12, and food is plentiful. What does 30 represent?

96.Rabbit counts in one field over six years were 8, 16, 28, 31, 30, and 29. Food and space stayed about the same. What does the pattern show?

97.A canyon can support about 50 deer over time. After a mild winter, the herd numbers 80. What is most likely to happen next?

98.Wolves are removed from a valley where they hunted deer. What is the most likely short-term change?

99.A fungus kills most of the clover in a pasture. Rabbits in that pasture eat clover as their main food. What is the most likely effect on the rabbits?

100.Snakes that eat mice become rare in a grassland. The mice eat grass seeds. What is the most likely later effect on the grass?

101.A leaf is in bright sunlight and is photosynthesizing. Which gas exchange matches that process?

102.A student says a plant in bright light gives off only carbon dioxide, the way a person breathes out. What is the best correction?

103.A watered plant is left in a dark closet for two days. Why does photosynthesis stop?

104.A class writes this word equation for photosynthesis: carbon dioxide + water -> sugar + oxygen, using light. Which product is the gas released?

105.A flood makes a pond so muddy that sunlight cannot reach the algae. Minnows in the pond eat the algae. What is the most likely result?

106.Decomposers break down a pile of dead leaves. Nutrients from the leaves return to the soil, and plants later take them up. Which statement is correct?

107.A table shows plants storing 12,000 kJ, insects that eat the plants storing 1,200 kJ, and frogs that eat the insects storing 120 kJ. About how much energy would snakes that eat the frogs store?

108.A drought sharply cuts rainfall in a grassland. The grass grows poorly. Grasshoppers there eat the grass. What is the most likely effect on the grasshoppers?