Two big ideas in one article
Grade 7 Reading Worksheet - Challenge Me
Circle the best answer.
Read this first
Salt on Winter Roads (article)
[1] Crews spread salt on icy roads because it lowers the freezing point of water, so ice melts at temperatures where plain water would stay frozen. [2] Even a thin layer of ice can turn a road into a skating rink, and salt has made winter driving safer in many cold regions. [3] Bridges and hills matter most, because cars are more likely to slide there.
[4] But the salt does not simply disappear after the ice melts. [5] Rain and melting snow wash it into roadside soil and nearby streams, where it raises the saltiness of the water. [6] Many freshwater plants and animals cannot cope with that change, and salty soil can also stunt trees along a highway.
[7] Salt also stops working well when the air turns extremely cold, around fifteen degrees Fahrenheit and below for common rock salt. [8] Crews sometimes switch to sand for grip or to other chemicals, which usually cost more. [9] Meanwhile, each scoop of salt still travels the same path toward the streams.
[10] Because of these problems, some road crews now spray a salty liquid before a storm instead of spreading dry salt afterward. [11] This method needs less salt to keep ice from bonding to the pavement. [12] Cities that track how much salt they use can protect their roads and still limit the harm downstream.
Milo reads the article and tries to name its two central ideas. Which choice states both of them?
- Salt melts ice by lowering its freezing point, and it works poorly once the air turns extremely cold.
- Salt makes icy roads safer by melting ice, and sand adds grip when the air turns extremely cold.
- Salt makes icy roads safer by melting ice, and its runoff has turned most streams too salty for fish.
- Salt makes icy roads safer by melting ice, and the salt that washes away can harm plants and streams.
Noah is tracing the central idea that road salt washes into soil and streams and harms plants and animals. Which choice describes how the article develops that idea?
- It traces the salt from the road into soil and streams, then shows crews trying to use less of it.
- It traces the salt from the road into streams, then shows the harm ending once crews use liquid brine.
- It names one harm, stunted trees beside highways, and treats that one example as the whole idea.
- It traces the salt from the truck onto the ice, then shows crews switching to sand in extreme cold.
Pia is comparing the article's two central ideas. Which choice explains how the article connects them?
- The two ideas stay separate, because the article describes crews' methods without linking them to the damage.
- The ideas meet where the article says salt stops working well in extreme cold.
- The harm from salt gives crews a reason to change how they apply it while still keeping roads safe.
- The harm from salt shows that crews should stop using it and rely on sand instead.
Beavers and the Land (article)
[1] Beavers cut down trees and pile logs, branches and mud across streams to build dams. [2] Behind a dam, the moving water slows and spreads into a pond, which gives the beavers a safe place for their lodge. [3] The pond also covers ground that was dry, so the stream's landscape begins to change.
[4] That change can cause trouble when the pond rises near a road or farm. [5] A dam may block a culvert, the pipe that carries a stream under a road, so water backs up and floods the pavement. [6] Beavers may also cut down trees that people planted in yards or along fields.
[7] Over time, though, many beaver ponds become wetlands where frogs, ducks, fish and insects find food and shelter. [8] A series of dams can hold back water during heavy rain and release it slowly afterward, which may help streams keep flowing in dry weather. [9] Some scientists study beaver ponds as a way to restore streams that people have damaged.
[10] Rather than removing every beaver, some towns now install flow devices, which are pipes that let water pass through a dam at a safe level. [11] The pond stays, the road stays dry, and the beavers keep their home. [12] Wire fences around valuable trees protect them from being cut.
Tala reads the article and tries to name its two central ideas. Which choice states both of them?
- Beaver dams create ponds and wetlands that help wildlife and water supplies, and a blocked culvert can flood a road.
- Beavers build dams from logs and mud, and the ponds behind them cover ground that was dry.
- Beaver dams create ponds and wetlands that help wildlife and water supplies, but the ponds can flood roads and farms.
- Beaver dams create ponds that help wildlife, and towns have removed beavers from most streams because floods cost too much.
Zee is comparing the article's two central ideas. Which choice explains how the article connects them?
- Towns want the benefits of the ponds without the flooding, so they add devices that control the water level.
- The benefits and the troubles are separate matters, because the pond causes one and the dam causes the other.
- The troubles outweigh the benefits, so the article advises towns to take out the dams near roads.
- Both ideas meet at the culvert, where a dam blocks a pipe and a pond floods the pavement.
Lichens
Two Lives in One (article): [1] A lichen looks like a single crusty patch on a rock or a tree trunk, but it is really two kinds of living things working together. [2] A fungus forms the body and holds water, while tiny algae living inside it use sunlight to make sugar. [3] The fungus shelters the algae and the algae feed the fungus, so each partner supplies what the other lacks.
[4] Many lichens are also sensitive to air pollution, which is why scientists pay attention to them. [5] In cities with heavy smoke, some kinds disappear from trees where they once grew. [6] When the air becomes cleaner, certain kinds slowly return.
[7] The partnership helps explain this sensitivity. [8] Lichens have no roots, so they take in water and dissolved substances directly through their surfaces from rain and air. [9] Pollutants dissolved in that water enter along with everything else, and some of them can damage the algae.
[10] Lichens often grow only a few millimeters in a year, so their communities change over long spans of time. [11] Researchers can count the kinds on a tree and compare them with other places to judge how clean the air is. [12] This kind of survey does not always tell which pollutant is present, but it gives a quick, low-cost picture of air quality.
Ari is comparing the article's two central ideas. Which choice explains how the article connects them?
- The sensitivity explains the partnership, since lichens team up with algae to escape polluted air.
- The sensitivity shows that the partnership is weak, since most lichens cannot survive wherever pollution is present.
- The way the partners live explains the sensitivity, since a lichen takes in air and water through its whole surface.
- Both ideas depend on how slowly lichens grow, which the last paragraph describes.
Bo reads the article and tries to name its two central ideas. Which choice states both of them?
- A lichen is a partnership of a fungus and algae, and a lichen survey names the exact pollutant in the air.
- A lichen is a partnership of a fungus and algae, and its sensitivity to pollution lets scientists judge air quality.
- A lichen is a partnership of a fungus and algae, and the fungus shelters the algae while the algae feed the fungus.
- A lichen is a partnership of a fungus and algae, and some kinds disappear from the trees of smoky cities.
Esme is tracing the central idea that lichens are sensitive to pollution and so show how clean the air is. Which choice describes how the article develops that idea?
- It names the partnership, shows what each partner supplies, then explains how the algae make sugar.
- It names the sensitivity, explains it through how lichens take in substances, then shows scientists using surveys.
- It explains the sensitivity, then shows that a lichen survey can name each pollutant in the air.
- It reports that some kinds vanish from smoky cities, then treats that one fact as the whole idea.
How a Hot-Air Balloon Is Flown (article)
[1] A hot-air balloon floats because the air inside its envelope is warmer than the air outside. [2] Heating makes air spread out, so a given volume of it weighs less than the same volume of cooler air. [3] When the balloon, basket and passengers together weigh less than the air they push aside, the whole craft rises.
[4] Direction is a different matter, because a balloon has no engine or rudder. [5] It moves with the wind, drifting at about the same speed as the air around it. [6] A pilot cannot turn a balloon the way a driver turns a car.
[7] What the pilot can control is height. [8] A burner adds heat to rise, and a vent at the top lets hot air out so the balloon descends. [9] Because winds often blow in different directions at different heights, a change in altitude can change where the balloon drifts.
[10] This is why pilots study weather forecasts and wind reports before every flight. [11] They look for a layer of air that will carry them toward a safe landing field. [12] If the winds are too strong or too unpredictable, they stay on the ground.
Kira is comparing the article's two central ideas. Which choice explains how the article connects them?
- The heating and venting that make a balloon rise or sink are also the pilot's way to steer, so the second idea builds on the first.
- Both ideas depend on weather forecasts, which the last paragraph describes.
- The second idea corrects the first, since the pilot must stop heating the air to go in any direction.
- The second idea shows that lift matters little, because the wind decides where a balloon goes.
Luz reads the article and tries to name its two central ideas. Which choice states both of them?
- A hot-air balloon rises because heated air is lighter, and a vent at the top lets hot air out.
- A hot-air balloon rises because heated air is lighter, and pilots steer by choosing a route before takeoff and keeping to it.
- A hot-air balloon rises because heated air is lighter, and pilots steer by changing height to catch different winds.
- A hot-air balloon rises because heated air is lighter, and the whole craft must weigh less than the air it pushes aside.