Free STAAR Grade 8 Science Practice Questions

1. Which of the following elements are ordered from least reactive to most reactive according to the Periodic Table?

  1. Ar, Cu, Na
  2. Na, Ar, Cu
  3. Na, Cu, Ar
  4. Ar, Na, Cu

2. Evidence of a chemical reaction can be determined by all of the following except?

  1. Modifying the arrangement of atoms
  2. Endothermic and exothermic reactions
  3. Equal masses of reactants and products
  4. No change in energy

3. Which of the following is a star with an absolute magnitude of +10 and a temperature of 25,000K?

  1. Main Sequence
  2. Super Giant
  3. Giant
  4. White Dwarf

4. Which of the following below is not considered evidence of plate tectonics?

  1. The shape of continents fits together like a puzzle
  2. Fossil comparisons exist along where the continents would fit together
  3. The Mid-Atlantic Ridge shows where new crust is formed
  4. There is a large amount of inland seismic activity

5. On December 22 of every year, the people in the southern hemisphere of the earth experience which event?

  1. Summer Solstice
  2. Winter Solstice
  3. Spring Equinox
  4. Fall Equinox

6. Our planet's oceans are experiencing climate changes, pollution, and overfishing. Which of the following answers is not a result of human activity?

  1. Diminishment of coral reefs
  2. Destruction of food webs
  3. Increased population of all species
  4. Degradation or total loss of wetlands

7. In mosses, eggs and sperm are produced by:

  1. Spores
  2. Sporophytes
  3. Gametophytes
  4. Zygotes

8. Which statement correctly states the work-energy theorem?

  1. The change in kinetic energy of an object is equal to the work done by the object
  2. The change in kinetic energy of an object is equal to the work done on an object
  3. The change in potential energy of an object is equal to the work done by the object
  4. The change in potential energy of an object is equal to the work done on an object

9. Balance the following reaction between sulfuric acid and aluminum hydroxide by filling in the correct stoichiometric values for each chemical.

_ H2SO4 + _ Al(OH)3 => _ Al2(SO4)3 + _ H2O

  1. 3, 2, 1, 6
  2. 2, 3, 1, 3
  3. 3, 3, 2, 6
  4. 1, 2, 1, 4

10. Which of the following situations would result in the generation of new crust?

  1. Two crustal plates converge
  2. Two crustal plates move apart
  3. Two crustal plates slide past one another
  4. A crustal plate is pushed down into the mantle

Grade 8 Science Answer Key

1. Answer: A
The Periodic Table's two most reactive groups are Group 1 and Group 17; therefore, Na, found in Group 1, would be the most reactive of the three elements. The element Cu is found in Group 11, which marks it as a transition metal, and is only somewhat reactive. Group 18, which includes Ar, contains the Noble Gases, which are not at all reactive.

2. Answer: D
A chemical reaction will always have an endothermic (absorb energy) or exothermic (release energy) reaction, and a chemical formula must always be balanced. Therefore, the masses of the reactants and products will always be equal, resulting in the modification of the atoms arrangement and a change in energy.

3. Answer: B
The work-energy theorem can be written W = KE. It is derived from Newton's second law (F = ma) by multiplying both sides by the distance the object moves. This work is the work done by a force on an object, and not the work done by an object. Work is only done by an object if that object exerts a force on another object, causing a change in its kinetic energy or position. The work done on an object MAY equal its potential energy, but only if that potential energy is converted into kinetic energy. In real-life cases, some energy is converted to heat, for example, so the change in potential energy does not equal the change in kinetic energy.

4. Answer: D
Evidence of plate tectonics is based on the shapes of the continents, which seem to fit together like a puzzle, as well as the fossils found along these edges. The Mid-Atlantic Ridge is the birthplace of new crust that is then destroyed in the subduction zones in the Pacific Ring of Fire, where most seismic activity takes place.

5. Answer: A
Due to the earth's tilt on its axis, the two hemispheres experience different seasons at opposite times because when one is pointed toward the sun, the other is facing away. In the Northern Hemisphere, winter occurs in December and summer in July. In the Southern Hemisphere, it is the opposite. The two Equinoxes occur oppositely for each hemisphere as well.

6. Answer: C
Human activities have not influenced the increased population of all species but have all played a role in the other environmental issues. As wetlands are degraded or lost, many ecosystems and species will also be lost, interrupting their respective food webs. Food webs within the actual oceans will also be reduced due to pollution and climate changes that impact water temperatures and levels. The diminishment of coral reefs means the ocean's water filtration system will be reduced or totally destroyed, affecting the ecosystems themselves as well as the organisms that use the area for breeding and feeding.

7. Answer: C
In plants, all eggs and sperm are produced by gametophytes. In mosses, the gametophyte is the most prominent stage. In angiosperms, gametophytes are tiny and found inside anthers and pistils.

8. Answer: B
The work-energy theorem can be written W = KE. It is derived from Newton's second law (F = ma) by multiplying both sides by the distance the object moves. This work is the work done by a force on an object, and not the work done by an object. Work is only done by an object if that object exerts a force on another object, causing a change in its kinetic energy or position. The work done on an object MAY equal its potential energy, but only if that potential energy is converted into kinetic energy. In real-life cases, some energy is converted to heat, for example, so the change in potential energy does not equal the change in kinetic energy.

9. Answer: A
By comparing the products to the reactants, there must be at least two Al atoms in the starting material, and at least three sulfate groups. Therefore, a coefficient of 2 must be placed in front of Al(OH)3 and a coefficient of 3 must be placed in front of H2SO4. To make the number of hydrogen and oxygen atoms equal on both sides of the equation, a coefficient of 6 must be placed in front of H2O.

10. Answer: B
Two crustal plates move apart. When two crustal plates move apart, magma welling up could result in the formation of new crust. This has been shown to be occurring on the ocean floor where places of the crust are weaker. The crust spreads apart at these trenches, pushing outward and erupting at the ridges. When two crustal plates converge, sublimation occurs as one plate runs under another pushing it up. Two crustal plates slide past one another, is an example of a transform fault, which does not create new crust. A crustal plate is pushed down into the mantle, does not form new crust but perhaps recycles the old one.

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Last Updated: 04/18/2018