examples0

id: 470

lecture: A solution is made up of two or more substances that are completely mixed. In a solution, solute particles are mixed into a solvent. The solute cannot be separated from the solvent by a filter. For example, if you stir a spoonful of salt into a cup of water, the salt will mix into the water to make a saltwater solution. In this case, the salt is the solute. The water is the solvent. The concentration of a solute in a solution is a measure of the ratio of solute to solvent. Concentration can be described in terms of particles of solute per volume of solvent. concentration = particles of solute / volume of solvent

question: Which solution has a higher concentration of green particles?

choice: (A) Solution B (B) neither; their concentrations are the same (C) Solution A

context: The diagram below is a model of two solutions. Each green ball represents one particle of solute.

answer: B

rationale: A solution is made up of two or more substances that are completely mixed. In a solution, solute particles are mixed into a solvent. The solute cannot be separated from the solvent by a filter. For example, if you stir a spoonful of salt into a cup of water, the salt will mix into the water to make a saltwater solution. In this case, the salt is the solute. The water is the solvent. The concentration of a solute in a solution is a measure of the ratio of solute to solvent. Concentration can be described in terms of particles of solute per volume of solvent. concentration = particles of solute / volume of solvent In Solution A and Solution B, the green particles represent the solute. To figure out which solution has a higher concentration of green particles, look at both the number of green particles and the volume of the solvent in each container. Use the concentration formula to find the number of green particles per milliliter. Solution A has more green particles per milliliter. So, Solution A has a higher concentration of green particles. The answer is C.

generated_skill:

solution: In Solution A and Solution B, the green particles represent the solute. To figure out which solution has a higher concentration of green particles, look at both the number of green particles and the volume of the solvent in each container. Use the concentration formula to find the number of green particles per milliliter. Solution A and Solution B have the same number of green particles per milliliter. So, their concentrations are the same.

skill: Compare concentrations of solutions

id: 841

lecture: A food web is a model. A food web shows where organisms in an ecosystem get their food. Models can make things in nature easier to understand because models can represent complex things in a simpler way. If a food web showed every organism in an ecosystem, the food web would be hard to understand. So, each food web shows how some organisms in an ecosystem can get their food. Arrows show how matter moves. A food web has arrows that point from one organism to another. Each arrow shows the direction that matter moves when one organism eats another organism. An arrow starts from the organism that is eaten. The arrow points to the organism that is doing the eating. An organism in a food web can have more than one arrow pointing from it. This shows that the organism is eaten by more than one other organism in the food web. An organism in a food web can also have more than one arrow pointing to it. This shows that the organism eats more than one other organism in the food web.

question: Which of these organisms contains matter that was once part of the lichen?

choice: (A) mushroom (B) short-tailed weasel (C) brown lemming (D) rough-legged hawk (E) bilberry

context: Below is a food web from a tundra ecosystem in Nunavut, a territory in Northern Canada. A food web models how the matter eaten by organisms moves through an ecosystem. The arrows in a food web represent how matter moves between organisms in an ecosystem.

answer: A

rationale: A food web is a model. A food web shows where organisms in an ecosystem get their food. Models can make things in nature easier to understand because models can represent complex things in a simpler way. If a food web showed every organism in an ecosystem, the food web would be hard to understand. So, each food web shows how some organisms in an ecosystem can get their food. Arrows show how matter moves. A food web has arrows that point from one organism to another. Each arrow shows the direction that matter moves when one organism eats another organism. An arrow starts from the organism that is eaten. The arrow points to the organism that is doing the eating. An organism in a food web can have more than one arrow pointing from it. This shows that the organism is eaten by more than one other organism in the food web. An organism in a food web can also have more than one arrow pointing to it. This shows that the organism eats more than one other organism in the food web. Use the arrows to follow how matter moves through this food web. For each answer choice, try to find a path of arrows that starts from the lichen. The only arrow pointing to the short-tailed weasel starts from the brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the short-tailed weasel.There is one path matter can take from the lichen to the rough-legged hawk: lichen->barren-ground caribou->rough-legged hawk. There are two paths matter can take from the lichen to the mushroom: lichen->barren-ground caribou->mushroom. lichen->barren-ground caribou->grizzly bear->mushroom. brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the brown lemming.. bilberry. The bilberry does not have any arrows pointing to it. So, in this food web, matter does not move from the lichen to the bilberry.. The answer is E.

generated_skill:

solution: Use the arrows to follow how matter moves through this food web. For each answer choice, try to find a path of arrows that starts from the lichen. The bilberry does not have any arrows pointing to it. So, in this food web, matter does not move from the lichen to the bilberry.There are two paths matter can take from the lichen to the mushroom: lichen->barren-ground caribou->mushroom. lichen->barren-ground caribou->grizzly bear->mushroom. brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the brown lemming.. short-tailed weasel. The only arrow pointing to the short-tailed weasel starts from the brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the short-tailed weasel.. rough-legged hawk. The only arrow pointing to the rough-legged hawk starts from the parasitic jaeger. The only arrow pointing to the parasitic jaeger starts from the brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the rough-legged hawk..

skill: Interpret food webs II

id: 1009

lecture: The temperature of a substance depends on the average kinetic energy of the particles in the substance. The higher the average kinetic energy of the particles, the higher the temperature of the substance. The kinetic energy of a particle is determined by its mass and speed. For a pure substance, the greater the mass of each particle in the substance and the higher the average speed of the particles, the higher their average kinetic energy.

question: Compare the average kinetic energies of the particles in each sample. Which sample has the higher temperature?

choice: (A) neither; the samples have the same temperature (B) sample B (C) sample A

context: The diagrams below show two pure samples of gas in identical closed, rigid containers. Each colored ball represents one gas particle. Both samples have the same number of particles.

answer: B

rationale: The temperature of a substance depends on the average kinetic energy of the particles in the substance. The higher the average kinetic energy of the particles, the higher the temperature of the substance. The kinetic energy of a particle is determined by its mass and speed. For a pure substance, the greater the mass of each particle in the substance and the higher the average speed of the particles, the higher their average kinetic energy. The particles in both samples have the same average speed, but each particle in sample A has more mass than each particle in sample B. So, the particles in sample A have a higher average kinetic energy than the particles in sample B. Because the particles in sample A have the higher average kinetic energy, sample A must have the higher temperature. The answer is C.

generated_skill:

solution: The particles in both samples have the same average speed, but each particle in sample B has more mass than each particle in sample A. So, the particles in sample B have a higher average kinetic energy than the particles in sample A. Because the particles in sample B have the higher average kinetic energy, sample B must have the higher temperature.

skill: Identify how particle motion affects temperature and pressure

id: 1014

question: Which solution has a higher concentration of green particles?

choice: (A) Solution B (B) neither; their concentrations are the same (C) Solution A

context: The diagram below is a model of two solutions. Each green ball represents one particle of solute.

answer: B

generated_skill:

skill: Compare concentrations of solutions

id: 1816

question: Which of the following organisms is the omnivore in this food web?

choice: (A) black racer (B) gray fox (C) silver maple (D) black bear

context: Below is a food web from Shenandoah National Park, a forest ecosystem in Virginia. A food web models how the matter eaten by organisms moves through an ecosystem. The arrows in a food web represent how matter moves between organisms in an ecosystem.

answer: D

rationale: A food web is a model. A food web shows where organisms in an ecosystem get their food. Models can make things in nature easier to understand because models can represent complex things in a simpler way. If a food web showed every organism in an ecosystem, the food web would be hard to understand. So, each food web shows how some organisms in an ecosystem can get their food. Arrows show how matter moves. A food web has arrows that point from one organism to another. Each arrow shows the direction that matter moves when one organism eats another organism. An arrow starts from the organism that is eaten. The arrow points to the organism that is doing the eating. An organism in a food web can have more than one arrow pointing from it. This shows that the organism is eaten by more than one other organism in the food web. An organism in a food web can also have more than one arrow pointing to it. This shows that the organism eats more than one other organism in the food web. Omnivores are consumers that eat both producers and other consumers. So, an omnivore has arrows pointing to it from at least one producer and at least one consumer. The silver maple does not have any arrows pointing to it. So, the silver maple is not an omnivore. The black bear has an arrow pointing to it from the persimmon tree, which is a producer. The black bear also has an arrow pointing to it from the swallowtail caterpillar, which is a consumer. The black bear eats a producer and a consumer, so it is an omnivore. The gray fox has an arrow pointing to it from the swallowtail caterpillar, which is a consumer. The gray fox also has an arrow pointing to it from the pine vole, which is a producer. The gray fox eats a producer and a consumer, so it is an omnivore. The black racer has only one arrow pointing to it. This arrow starts from the pine vole, which is a producer. So, the black racer is a consumer but not an omnivore. The answer is B.

generated_skill:

solution: Omnivores are consumers that eat both producers and other consumers. So, an omnivore has arrows pointing to it from at least one producer and at least one consumer. The black bear has an arrow pointing to it from the persimmon tree, which is a producer. The black bear also has arrows pointing to it from the swallowtail caterpillar and the beaver, which are consumers. The black bear eats a producer and consumers, so it is an omnivore. The gray fox has two arrows pointing to it. These arrows start from the swallowtail caterpillar and the pine vole, which are both consumers. So, the gray fox is a consumer but not an omnivore. The pine vole has an arrow pointing to it from the persimmon tree, which is a producer. The pine vole also has an arrow pointing to it from the swallowtail caterpillar, which is a consumer. The pine vole eats a producer and a consumer, so it is an omnivore. The silver maple does not have any arrows pointing to it. So, the silver maple is not an omnivore. The black racer has only one arrow pointing to it. This arrow starts from the pine vole, which is a consumer. So, the black racer is a consumer but not an omnivore.

skill: Interpret food webs I

id: 2332

lecture: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. Whether a magnet attracts or repels other magnets depends on the positions of its poles, or ends. Every magnet has two poles, called north and south. Here are some examples of magnets. The north pole of each magnet is marked N, and the south pole is marked S. If different poles are closest to each other, the magnets attract. The magnets in the pair below attract. If the same poles are closest to each other, the magnets repel. The magnets in both pairs below repel.

question: Will these magnets attract or repel each other?

choice: (A) repel (B) attract

context: Two magnets are placed as shown. Hint: Magnets that attract pull together. Magnets that repel push apart.

answer: A

rationale: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. Whether a magnet attracts or repels other magnets depends on the positions of its poles, or ends. Every magnet has two poles, called north and south. Here are some examples of magnets. The north pole of each magnet is marked N, and the south pole is marked S. If different poles are closest to each other, the magnets attract. The magnets in the pair below attract. If the same poles are closest to each other, the magnets repel. The magnets in both pairs below repel. Will these magnets attract or repel? To find out, look at which poles are closest to each other. The north pole of one magnet is closest to the south pole of the other magnet. Poles that are different attract. So, these magnets will attract each other. The answer is B.

generated_skill:

solution: Will these magnets attract or repel? To find out, look at which poles are closest to each other. The north pole of one magnet is closest to the north pole of the other magnet. Poles that are the same repel. So, these magnets will repel each other.

skill: Identify magnets that attract or repel

id: 2983

question: Which solution has a higher concentration of green particles?

choice: (A) Solution A (B) neither; their concentrations are the same (C) Solution B

context: The diagram below is a model of two solutions. Each green ball represents one particle of solute.

answer: C

generated_skill:

solution: In Solution A and Solution B, the green particles represent the solute. To figure out which solution has a higher concentration of green particles, look at both the number of green particles and the volume of the solvent in each container. Use the concentration formula to find the number of green particles per milliliter. Solution B has more green particles per milliliter. So, Solution B has a higher concentration of green particles.

skill: Compare concentrations of solutions

id: 2993

lecture:

question: Which state is highlighted?

choice: (A) Nebraska (B) North Dakota (C) Michigan (D) Minnesota

context: N/A

answer: B

rationale: This state is Nebraska. The answer is A.

generated_skill:

solution: This state is North Dakota.

skill: Identify states of the Midwest

id: 3036

question: Compare the average kinetic energies of the particles in each sample. Which sample has the higher temperature?

choice: (A) neither; the samples have the same temperature (B) sample A (C) sample B

context: The diagrams below show two pure samples of gas in identical closed, rigid containers. Each colored ball represents one gas particle. Both samples have the same number of particles.

answer: A

rationale: The temperature of a substance depends on the average kinetic energy of the particles in the substance. The higher the average kinetic energy of the particles, the higher the temperature of the substance. The kinetic energy of a particle is determined by its mass and speed. For a pure substance, the greater the mass of each particle in the substance and the higher the average speed of the particles, the higher their average kinetic energy. Each particle in the two samples has the same mass, but the particles in sample B have a higher average speed than the particles in sample A. So, the particles in sample B have a higher average kinetic energy than the particles in sample A. Because the particles in sample B have the higher average kinetic energy, sample B must have the higher temperature. The answer is C.

generated_skill:

solution: Each particle in the two samples has the same mass, and the particles in both samples have the same average speed. So, the particles in both samples have the same average kinetic energy. Because the particles in both samples have the same average kinetic energy, the samples must have the same temperature.

skill: Identify how particle motion affects temperature and pressure

id: 3118

lecture: A fossil is the preserved evidence of an ancient organism. Some fossils are formed from body parts such as bones or shells. Other fossils, such as footprints or burrows, are formed from traces of an organism's activities. Fossils are typically found in sedimentary rocks. Sedimentary rocks usually form in layers. Over time, new layers are added on top of old layers in a series called a rock sequence. The layers in an undisturbed rock sequence are in the same order as when they formed. So, the deeper layers are older than the shallower layers. The relative ages of fossils can be determined from their positions in an undisturbed rock sequence. Older fossils are usually in deeper layers, and younger fossils are usually in shallower layers.

question: Which of the following fossils is older? Select the more likely answer.

choice: (A) ginkgo leaf (B) insect

context: This diagram shows fossils in an undisturbed sedimentary rock sequence.

answer: A

rationale: A fossil is the preserved evidence of an ancient organism. Some fossils are formed from body parts such as bones or shells. Other fossils, such as footprints or burrows, are formed from traces of an organism's activities. Fossils are typically found in sedimentary rocks. Sedimentary rocks usually form in layers. Over time, new layers are added on top of old layers in a series called a rock sequence. The layers in an undisturbed rock sequence are in the same order as when they formed. So, the deeper layers are older than the shallower layers. The relative ages of fossils can be determined from their positions in an undisturbed rock sequence. Older fossils are usually in deeper layers, and younger fossils are usually in shallower layers. Look again at the fossils in the rock sequence diagram. Compare the positions of these fossils to determine which one is older: The insect fossil is in a deeper layer in the rock sequence than the ginkgo leaf fossil. So, the insect fossil is most likely older than the ginkgo leaf fossil. The answer is B.

generated_skill:

solution: Look again at the fossils in the rock sequence diagram. Compare the positions of these fossils to determine which one is older: The ginkgo leaf fossil is in a deeper layer in the rock sequence than the insect fossil. So, the ginkgo leaf fossil is most likely older than the insect fossil.

skill: Compare ages of fossils in a rock sequence