Explain a topic or a process in a few paragraphs

Grade 8 Reading Worksheet

Circle the best answer.

1. Read this first

   Why the Sky Changes Color (explanatory draft)

   [1] On a clear day the sky looks deep blue, yet at sunset the same sky glows with orange and red light. [2] The color of the sky depends on how sunlight meets the gases and tiny particles that make up Earth's atmosphere. [3] Sunlight looks white, but it is really a mixture of all the colors of the rainbow, from red at one end to violet at the other. [4] Each color travels as a wave of a different length, and blue light has a much shorter wavelength than red light does.

   [5] Blue light is scattered the most by the gas molecules, and the daytime sky looks blue. [6] That scattered blue light reaches our eyes from every part of the sky at midday, so the whole dome looks blue. [7] The sunset sky is full of stuff that changes the colors. [8] What remains in the beam are the longer waves, which our eyes see as orange and red.

   [9] That is also part of the answer. [10] The same sunlight, the same atmosphere, and the same process of scattering produce both the blue sky of noon and the red sky of sunset. [11] Only the length of the path that the sunlight takes through the air has changed.

2. 1.

   Noah thinks sentence [5] does not show how its two ideas connect. Which version shows the cause and the effect correctly?

   • Gas molecules scatter blue light far more than red light. The sky looks blue.
   • Because the sky looks blue, gas molecules scatter blue light far more than red light.
   • Although gas molecules scatter blue light far more than red light, the sky looks blue.
   • Because gas molecules scatter blue light far more than red light, the sky looks blue.
3. 2.

   Ren sees that the essay explains why the sky is blue and then red. Which sentence should replace sentence [9] to add the next link in the chain?

   • Other planets have skies of different colors because their gases differ from the gases on Earth.
   • Clouds look white because the water drops in them scatter the different colors of light about equally.
   • Sunlight is a mixture of the colors of the rainbow, and blue light has a shorter wavelength than red light.
   • As a result, the sky near the horizon glows orange and red, while the sky overhead may still look blue.

4. How a Coral Reef Is Built (explanatory draft)

   [1] A coral reef looks like a rock garden under the sea, but it is built entirely by living animals. [2] Reefs form because tiny animals called coral polyps build hard skeletons that pile up over many years. [3] Each polyp takes calcium from seawater and makes a cup of limestone around its soft body. [4] When a polyp dies, its limestone cup stays behind, and new polyps build on top of it, layer by layer.

   [5] Reef-building polyps live in warm, shallow, clear water because they depend on tiny algae that live inside their tissues. [6] The algae use sunlight to make food and share some of it with the polyp. [7] Corals need sunlight, so reefs grow in shallow water. [8] Lots of sea animals like hanging around the reef for the stuff it gives them.

   [9] There is more to say about this. [10] From one tiny polyp to a whole reef, each step depends on the step before it.

5. 3.

   Tala thinks sentence [7] does not show how its two ideas connect. Which version shows the cause and the effect correctly?

   • Because the algae inside the polyps need sunlight to make food, reefs grow in shallow water where light can reach them.
   • The algae inside the polyps need sunlight to make food. Reefs grow in shallow water.
   • Because reefs grow in shallow water, the algae inside the polyps need sunlight to make food.
   • Although the algae inside the polyps need sunlight to make food, reefs grow in shallow water.
6. 4.

   Zee thinks sentence [8] uses vague words. Which sentence should replace it with exact words in a formal voice?

   • Lots of sea creatures like the reef because it has a bunch of good places for them to be.
   • Coral skeletons are made of calcium carbonate, which is the same material as limestone.
   • Fish hide among the branching corals, and crabs and shrimp find food and shelter in the cracks of the reef.
   • Fish totally love the reef, and crabs and shrimp pile in like it is the world's coolest hotel for sea creatures.
7. 5.

   Ari sees that the essay explains how a reef grows. Which sentence should replace sentence [9] to add the next link in the chain?

   • Each polyp takes calcium from seawater and builds a cup of limestone around its soft body.
   • The Great Barrier Reef is the largest reef system in the world and lies off the coast of Australia.
   • If the water grows too warm, the polyps push out their algae, the coral turns white, and the reef can stop growing.
   • Many of the colors of a coral come from the algae that live inside the polyp's tissues.

8. How a Circuit Lights a Bulb (explanatory draft)

   [1] A lamp turns on when you press a switch, but the light depends on something invisible traveling through wires. [2] Electric charge can move only along a complete loop of connected materials, which is called a circuit. [3] A battery pushes the charge around the loop, and the wires, the bulb, and the switch are all parts of the path. [4] If any part of the loop is broken, the charge stops moving and the bulb goes dark.

   [5] Metals such as copper let charge flow easily, so they are called conductors, and manufacturers make wires out of them. [6] Materials such as rubber and plastic block the flow of charge, so they are called insulators. [7] The plastic outside a wire keeps the charge from going places it should not. [8] Closing the switch and the bulb lighting up are connected. [9] There is another thing to know.

   [10] A circuit works only when the right materials sit in the right places along a complete loop.

9. 6.

   Bo thinks sentence [8] does not show how its two ideas connect. Which version shows the cause and the effect correctly?

   • Because closing the switch completes the loop, charge can flow and the bulb lights up.
   • Because the bulb lights up, closing the switch completes the loop for the charge.
   • Closing the switch completes the loop. The bulb lights up.
   • Although closing the switch completes the loop, charge can flow and the bulb lights up.
10. 7.

    Jun sees that the essay explains how a circuit lights a bulb. Which sentence should replace sentence [9] to add the next link in the chain?

    • A battery pushes the charge around the loop, and the wires, the bulb, and the switch are parts of the path in a circuit.
    • Copper is used for wires because it is a good conductor and is easy to bend into shape.
    • Lightning is a huge natural spark that can jump through the air during a storm.
    • A fuse protects a circuit by melting when too much charge flows, which opens the loop before the wires can overheat.

11. Two Ways to Bring Water to a City (explanatory draft)

    [1] Every city needs a steady supply of fresh water, and builders in different ages have solved that problem in different ways. [2] Roman aqueducts and modern water systems both carry water to cities, but they differ in how they move the water and what carries it.

    [3] The Romans moved water with gravity alone. [4] The channel sloped downhill, and the water flowed. [5] Modern systems move water with pumps, which push it through pipes and can even lift it uphill to a water tower. [6] Roman builders carried their channels across valleys on tall stone arches that still stand in some places. [7] Modern systems have their own way of doing this.

    [8] Both systems depend on careful planning. [9] Roman engineers did a lot of figuring about the land, and modern engineers do a lot of figuring about the pressure. [10] Each system shows how builders use the forces of nature to bring water to people.

12. 8.

    Kira thinks sentence [4] does not show how its two ideas connect. Which version shows the cause and the effect correctly?

    • Although the channel sloped gently downhill for miles, gravity pulled the water along without any help.
    • Because the channel sloped gently downhill for miles, gravity pulled the water along without any help.
    • Because gravity pulled the water along without any help, the channel sloped gently downhill for miles.
    • The channel sloped gently downhill for miles. Gravity pulled the water along.
13. 9.

    Luz sees that the essay compares one feature at a time, and sentence [6] gives the Roman carrier. Which sentence should replace sentence [7] with the matching modern fact?

    • Roman builders carried their water in stone channels and across valleys on tall arches.
    • Water towers hold a large amount of water and often stand at the top of a hill.
    • Modern systems carry water in sealed pipes, usually buried under streets and sidewalks.
    • Modern systems use pumps to push the water through the pipes, even uphill to a tower.
14. 10.

    Milo thinks sentence [9] uses vague words. Which sentence should replace it with exact words in a formal voice?

    • Roman engineers surveyed the land to keep the slope gentle, and modern engineers calculate the pressure in the pipes.
    • The Pont du Gard, an aqueduct bridge in France, still stands after almost two thousand years.
    • Roman and modern engineers each had to work out a lot of numbers and details for their jobs.
    • Roman engineers had to be total land nerds, and modern engineers have to be math whizzes about pressure in the water pipes.