Explain a complex idea precisely

Grade 11 Reading Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   What Lights the Polar Sky (student informative essay draft)

   [1] On clear nights near the Arctic and the Antarctic, curtains of green and sometimes red or purple light ripple across the sky, a display called the aurora borealis in the north and the aurora australis in the south. [2] Atomic oxygen produces the most common green light, while oxygen at the highest altitudes gives off red light, and molecular nitrogen produces blue and purple. [3] The light appears high in the atmosphere, most often at heights of about 100 kilometers or more above the ground, far above the clouds and the weather. [4] Its ultimate source, however, lies about 150 million kilometers away, in the sun.

   [5] The sun constantly sends out a stream of charged particles known as the solar wind. [6] Earth's magnetic field turns most of these particles aside, but some of their energy feeds the magnetosphere, the region of space that the magnetic field controls. [7] Electrons accelerated in the magnetosphere then follow the lines of Earth's magnetic field down toward two oval-shaped zones centered roughly on the magnetic poles.

   [8] When these fast electrons strike the atoms and molecules of the thin upper atmosphere they transfer energy that raises the particles to excited states from which they fall back while emitting photons at wavelengths characteristic of each gas, which is the light. [9] This is the same kind of glow that appears in a neon sign, where electricity passing through a tube of gas makes the gas shine. [10] The colors therefore tell scientists which gases the electrons are striking, and at roughly what height.

   [11] During major geomagnetic storms, the two ovals expand away from the poles. [12] In large events, the aurora can be seen as far south as parts of the United States, Europe and Asia. [13] Other kinds of space weather can weaken high-frequency radio signals, so forecasters at the federal Space Weather Prediction Center watch the sun and issue alerts. [14] In conclusion, auroras are lights in the sky that come from the sun and the magnetic field.

2. 1.

   Ari sees that [2] names colors before the draft explains why gases glow. Where should [2] go so each sentence builds on the one before?

   • Move [2] to follow [12].
   • Move [2] to follow [3].
   • Keep [2] where it is, after [1].
   • Move [2] to follow [9].
3. 2.

   Bo sees that [14] just sums up. Which sentence should replace [14] so the conclusion states an implication of the explanation?

   • Because an aurora traces particles steered by Earth's magnetic field, the display is visible evidence that the field turns most of the solar wind away from the planet.
   • Because neon signs glow the same way, the aurora shows that neon lighting is one of the most scientific inventions of modern times.
   • Because the aurora begins at the sun, studying it closely will soon let scientists switch magnetic storms off long before they reach the upper atmosphere and disturb radio signals.
   • Spacecraft and space telescopes have also recorded auroras on other planets, including Jupiter and Mars.
4. 3.

   Sentence [8] crowds several steps into one. Esme wants a clear, accurate revision. Which two sentences should replace [8]?

   • Upon impact, the precipitating electrons collisionally excite the atomic and molecular constituents of the auroral thermosphere. Radiative de-excitation then yields photon emission at species-specific wavelengths.
   • When these fast electrons strike atoms and molecules in the thin upper air, they give those particles extra energy. Each particle soon releases that energy as light, and every gas gives off its own colors.
   • When these electrons reach the upper air, something happens to the gases that are floating there. As a result, the sky lights up in several different colors at once.
   • When these fast electrons strike atoms and molecules in the thin upper air, light appears. That light can be green, red, blue or purple.

5. How Escalator Stairs Turn Flat (student informative essay draft)

   [1] An escalator seems to perform a small trick at each end, since a row of solid stairs flattens into a level walkway, and a level walkway rises again into stairs. [2] The inventor Jesse Reno built the first working escalator, which was installed as an amusement ride at Coney Island in 1896, and Charles Seeberger produced the first commercial model three years later. [3] The trick depends on how each step is built and on the tracks that guide it.

   [4] Near the top and the bottom, the two tracks come together until the front and back wheels of each step run almost in a straight line. [5] Each step is a rigid unit with two sets of small wheels, one near the front edge of the step and one near the back. [6] The front wheels run along one track, and the back wheels run along a second track. [7] Along the sloping middle of the escalator, the two tracks run apart, so that each step's tread stays level while its neighbors sit higher and lower, forming stairs. [8] Each step then lies flat beside its neighbors, and together they form a level platform that a rider can step on or off.

   [9] The steps are linked in a loop by a chain, which is driven by a motor and a large gear that are usually housed beneath the top landing. [10] After a step passes the top landing, the tracks carry it back down along the underside of the escalator to the bottom, where it starts its climb again. [11] The handrail which is a separate loop of rubber and fabric driven through pulleys connected by a chain to the same main drive gear moves at the same speed as the steps because if it moved faster or slower the riders holding it would be pulled off balance.

   [12] Comb plates at each landing have teeth that fit between the grooves of the steps, so the gap stays very small. [13] The word "escalator" was registered as a trademark in 1900, but in 1950 the word lost that protection and became an ordinary noun. [14] So that is how escalators work, which is pretty interesting when you think about it.

6. 4.

   Kira sees that [14] adds nothing. Which sentence should replace [14] so the conclusion states an implication of the explanation?

   • Because the stairs are shaped by the tracks rather than by moving parts in each step, an escalator's smooth ride depends on keeping those tracks precisely aligned.
   • In short, wheels on two tracks form stairs on the slope and flatten the steps at each landing, while a chain pulls the loop.
   • Because the tracks shape the stairs, an escalator is a perfect machine that will not need repairs for as long as its building stands.
   • Because Seeberger's trademark was lost in 1950, the history of the escalator shows that inventors should guard their names with care.
7. 5.

   Sentence [11] crowds several ideas into one. Luz wants a clear, accurate revision. Which two sentences should replace [11]?

   • The handrail is pulled along by the riders who hold it, so it needs no motor or gear of its own at either landing of the escalator. Their grip keeps it moving at the same speed as the steps beneath them.
   • The handrail is a separate loop of rubber and fabric, but pulleys and a chain connect it to the same drive gear as the steps. That link keeps hands and feet moving at one speed, so riders stay balanced.
   • The handrail is connected to the escalator's machinery in some way. As a result, it moves along with the steps.
   • The handrail's drive is kinematically coupled to the main sprocket through a secondary chain and sheave train. Synchronous velocity prevents differential motion at the rider interface.

8. Multiplying by Sliding a Ruler (student informative essay draft)

   [1] Before pocket calculators became common, engineers, scientists and students multiplied numbers with a slide rule, a ruler-shaped instrument with a sliding center strip. [2] The instrument depends on logarithms, which the Scottish mathematician John Napier introduced in 1614. [3] A logarithm turns multiplication into addition, because the logarithm of a product equals the sum of the logarithms of the numbers being multiplied.

   [4] A slide rule gives that rule a physical form by placing each number at a distance from the starting mark proportional to its logarithm, rather than at equal steps. [5] On such a logarithmic scale, the marks crowd closer together toward the right, and the distance from 1 to 2 equals the distance from 2 to 4, since both stand for multiplying by two. [6] This is why a slide rule can find a product without its user multiplying a single pair of digits.

   [7] The two main scales, labeled C and D, each run from 1 to 10, one on the sliding strip and one on the body beside it, and a sliding cursor with a fine hairline helps the user line up the marks exactly. [8] To multiply 2 by 3 the user slides the C scale until its 1 sits directly above the 2 on the D scale and then finds the 3 on the C scale and reads the number beneath it on the D scale which is 6 because the two lengths have been laid end to end. [9] Adding the two lengths is the same as adding the two logarithms, so the end of the second length marks the logarithm of the product.

   [10] The scales show only the digits of an answer, so the user must work out separately where the decimal point belongs, deciding, for instance, whether the answer is 6, 60 or 600. [11] Answers are also limited to about three significant digits, since the user must estimate the last digit between two printed marks. [12] Edmund Gunter drew a single logarithmic scale in 1620, and William Oughtred is generally credited with placing two such scales side by side around 1622. [13] Inexpensive electronic scientific calculators appeared in the mid-1970s, and within a few years slide rules had largely disappeared from classrooms and offices. [14] To sum up, a slide rule multiplies numbers by sliding two scales.

9. 6.

   Milo sees that [6] states a result before the draft shows how the scales are used. Where should [6] go so each sentence builds on the one before?

   • Move [6] to follow [9].
   • Move [6] to follow [10].
   • Move [6] to follow [7].
   • Keep [6] where it is, after [5].
10. 7.

    Noah sees that [14] just sums up. Which sentence should replace [14] so the conclusion states an implication of the explanation?

    • Because calculators replaced slide rules within a few years, the main lesson is that newer machines tend to push older tools aside quickly.
    • Because the instrument multiplies by adding lengths, it shows that logarithms were a practical tool as well as an idea, letting people calculate by hand for some three hundred and fifty years.
    • William Oughtred also introduced the multiplication sign that mathematicians still use, in a book he published in 1631.
    • In short, logarithmic scales let a user lay two lengths end to end on the C and D scales and read the product beneath the second number.
11. 8.

    Sentence [8] crowds several steps into one. Pia wants a clear, accurate revision. Which two sentences should replace [8]?

    • To multiply 2 by 3, the user slides the C scale until its 1 sits directly above the 2 on the D scale. The D scale then reads 6 beneath the 3 on the C scale, because the two lengths have been laid end to end.
    • To multiply 2 by 3, the user finds the 3 on the C scale. The number beneath it on the D scale, 6, is then the product of the two numbers.
    • To multiply 2 by 3, the user slides the C scale until its 3 sits directly above the 2 on the D scale. The D scale then reads 6 beneath the 1 on the C scale, because the two lengths have been laid end to end.
    • To multiply 2 by 3, the user moves the sliding strip into the right position for the problem. The answer then appears somewhere on the lower scale.

12. How a Fountain Pen Feeds Ink (student informative essay draft)

    [1] A fountain pen holds a supply of liquid ink, yet it does not pour that ink onto the paper all at once or drip when it is held point-down, and the reason lies in a careful balance of small forces. [2] The ink sits in a reservoir inside the barrel of the pen, which may be a refillable chamber or a replaceable cartridge. [3] Between the reservoir and the paper are two parts: the feed, a piece with narrow channels cut along it, and the nib, the thin metal point that touches the paper.

    [4] The main force at work is capillary action, the tendency of a liquid to creep along a very narrow space. [5] Capillary action happens because the liquid is attracted to the walls of the space, and in a narrow enough channel that attraction can pull the liquid along even against gravity. [6] When the tip touches paper, the paper's fibers draw the ink out of the slit, and the pen leaves a line. [7] The same force draws water up a thin glass tube or into a paper towel.

    [8] Ink travels from the reservoir along a narrow channel in the feed to the underside of the nib. [9] The nib is split down the middle by a fine slit, and capillary action draws the ink along that slit to the very tip.

    [10] As ink leaves the reservoir air has to replace it or a partial vacuum would form and stop the flow so the feed also has grooves through which small bubbles of air travel back up into the reservoir in exchange for the ink that has flowed down which must stay balanced so the ink neither floods nor stops. [11] Most nibs are made of stainless steel or gold, and the point often carries a bead of very hard metal, called tipping, that resists wear. [12] A fountain pen needs ink made for it, since ordinary India ink contains a binder, shellac, that would quickly clog the narrow channels. [13] Fountain pens with feeds of this kind were already being patented in the United States by the 1880s. [14] That is basically the whole story of how a fountain pen works.

13. 9.

    Tala sees that [14] adds nothing. Which sentence should replace [14] so the conclusion states an implication of the explanation?

    • Because capillary action is so strong, a fountain pen can write upside down in any position for as long as anyone likes.
    • So capillary action carries ink through the feed and down the slit, and air returns to the reservoir as the ink leaves.
    • Ballpoint pens, which roll ink onto paper with a tiny ball, became popular in the years after World War II.
    • Because the pen depends on narrow channels and a steady trade of air for ink, a blockage in one small passage can stop it, which is why the channels must stay clean.
14. 10.

    Sentence [10] crowds several steps into one. Zee wants a clear, accurate revision. Which two sentences should replace [10]?

    • Volumetric ink egress induces negative headspace pressure within the reservoir. Counterflow air ingress through feed fissures restores equilibrium at a regulated rate.
    • As ink leaves the reservoir, the empty space fills with new ink that the pen makes from the air. Grooves in the feed carry this new ink down to the nib.
    • As ink leaves the reservoir, air must take its place, or a partial vacuum would form and stop the flow. Grooves in the feed let small bubbles of air travel up to the reservoir, trading air for ink at a balanced rate.
    • As ink leaves the reservoir, grooves in the feed carry it down toward the nib. The pen keeps writing until the ink runs out.