Explain a complex idea in an essay
Grade 9 Reading Worksheet - Building Confidence
Circle the best answer.
Read this first
How Soap Lifts Grease (informative draft)
[1] Water alone can rinse mud from a plate, but it runs straight off a greasy pan, because oil and water do not mix and the grease stays stuck to the metal. [2] Soap solves this problem, and the way it works depends on the unusual shape of the molecules that it is made of. [3] Soap is a surfactant, which is a word for something soap contains.
[4] One end of a soap molecule, called the head, is attracted to water, while the long tail at the other end is repelled by water and attracted to oil instead. [5] When soapy water touches a greasy surface, the tails push into the grease and the heads stay outside in the surrounding water. [6] Soap works because of the way its molecules are arranged around the grease. [7] Scientists call the tiny clusters that form in this way micelles, and each one is far too small to see without a powerful microscope.
[8] Scrubbing helps, since rubbing breaks large blobs of grease into smaller droplets that more soap molecules can surround. [9] Warm water also helps, because many greasy substances soften when they are heated and come away from a surface more easily. [10] Honestly, cold water is pretty useless for washing dishes, and nobody should even bother with it.
[11] The same process explains why washing hands with soap removes many germs, since the micelles carry off the oils and dirt that germs cling to. [12] Rinsing then carries the micelles, along with the grease and dirt trapped inside them, down the drain. [13] A bar of soap therefore does more than make bubbles, because each of its molecules acts as a bridge between two substances that would otherwise stay apart.
Ari sees that sentence [3] defines surfactant weakly. Which sentence gives an extended definition: what it is, how it differs from sugar in water, and an example?
- A surfactant is a substance whose molecules let water and oil, which normally stay in separate layers, mix together.
- A surfactant is a surface-active substance, which means that it is a kind of substance that is active on the surfaces of things, the way dish soap is.
- A surfactant is a substance that lets water mix with oil or grease; unlike sugar, which simply dissolves in water, it grips both, and dish soap is one example.
- Dish soap, shampoo, laundry powder and the bar of soap beside a kitchen sink are common examples of surfactants that are found in a home.
Paragraph 2 says soap lifts grease because of how its molecules are shaped. Bo wants a detail for [6]. Which detail shows how that shape lifts the grease?
- Hot water softens the grease on a pan, which makes it easier to wash away even before any soap has been added to the water.
- The tails crowd around each droplet of grease until it is wrapped in a ball of molecules whose heads face outward, so the water can carry it away.
- Once the soap has done its work, the grease no longer sticks to the pan, and it rinses away in the water and leaves the metal clean, smooth and shiny.
- The special two-ended shape of each soap molecule is the real reason that soap is able to lift grease from the surface of a pan.
Esme sees that sentence [10] slips into opinion and chat. Which version keeps the fact in an objective tone?
- Soap molecules stop working in cold water, so dishes washed that way stay as greasy as they were before they were rinsed.
- Cold water can still clean with soap, although washing in it is an unpleasant chore that sensible people avoid whenever they can.
- Cold water can still clean with soap, but grease usually comes away more slowly than it does in warm water.
- Cold water kind of works with soap, but the gunk takes way longer to come off than it does in warm water.
How Bicycle Gears Trade Speed for Ease (informative draft)
[1] A rider who pedals a bicycle up a steep hill and then coasts down the other side is asking the same machine to do two very different jobs. [2] Gears make both jobs possible, because they change how far the back wheel turns for each push on the pedals. [3] The key idea is the gear ratio, which is a ratio about gears.
[4] On most bicycles, the pedals turn a toothed wheel called a chainring, and a chain carries that motion back to a smaller toothed wheel, called a cog, on the rear hub. [5] If the chainring has 40 teeth and the cog has 20, the cog and the back wheel turn twice for every single turn of the pedals. [6] Many bicycles offer more than twenty combinations of chainring and cog, which gives a rider small steps between the easiest gear and the hardest one.
[7] Low gears make climbing easier because the rider's force is spread over a larger number of pedal turns. [8] Gears help a rider on a hill in a way that has to do with the chain. [9] The trade-off is speed, since in a very low gear the rider must spin the pedals quickly just to move at a walking pace.
[10] High gears work the opposite way, with a large chainring and a small cog, so that one turn of the pedals sends the bicycle a long distance. [11] On flat roads and downhill stretches, a high gear lets a rider travel fast without pedaling at a frantic speed. [12] Riders who are smart pick the right gear, and the ones who don't are just making things super hard for themselves. [13] Like a lever or a ramp, a set of gears creates no extra energy; it changes how the rider's effort is spent, trading force for distance.
Paragraph 3 says low gears make climbing easier because the force is spread over more pedal turns. Which detail for [8] shows Kira how?
- Spreading the rider's force over a larger number of pedal turns is what makes a low gear feel so much easier on a hill.
- Leaning forward over the handlebars on a steep climb keeps the front wheel steady on the road and stops the bicycle from tipping backward.
- With the chain on a small chainring and a large cog, each turn of the pedals moves the wheel a short way, so every push needs less force.
- In a low gear, a rider can reach the top of a steep hill without standing up on the pedals or stopping halfway up to rest.
Luz sees that sentence [12] judges riders in chatty words. Which version keeps the fact in an objective tone?
- Picking a gear that fits the hill is a total game changer, and you'll be way less wiped out by the time you reach the top.
- Choosing a gear that suits the slope is the habit of skilled riders, and careless riders who ignore it deserve their tired legs.
- Choosing a gear that suits the slope lets a rider keep a steady pace while using less effort over a long ride.
- Choosing the highest gear on each slope lets a rider climb faster while using less effort over a long ride.
How a Dam Turns Falling Water into Electricity (informative draft)
[1] A hydroelectric dam holds back a river and stores a huge amount of water in a lake behind a wall of concrete or packed earth. [2] That stored water has energy because of its height, and the dam's job is to turn that energy into electricity that can travel through power lines to homes and factories far away.
[3] Near the bottom of the dam, gates open to let water rush down through a large pipe called a penstock. [4] At the end of the pipe, the moving water strikes the blades of a turbine and makes it spin. [5] A turbine is the part that spins. [6] The turbine is joined by a long shaft to a generator, which sits above it inside the powerhouse.
[7] A generator makes electricity because of what happens between its magnets and its coils of wire. [8] It is something to do with the magnets that makes the electricity. [9] Machines called transformers then raise the voltage of that current, so that it can travel long distances with less energy lost along the way.
[10] The amount of electricity depends mostly on two things: how far the water falls and how much water flows through the turbines each second. [11] Hydroelectric power is totally awesome, and it's way better than any other kind of power plant. [12] Because the water is not burned or used up, it continues downstream after it leaves the turbines, and the lake refills with rain and melting snow. [13] A dam can also change the river below it, since it alters the flow and the temperature of the water and can block fish that swim upstream to lay their eggs.
Milo sees that sentence [5] barely defines turbine. Which sentence gives an extended definition: what it is, how it differs from a generator, and an example?
- A turbine is a wheel of angled blades that moving water, steam or wind pushes around; unlike a generator, it makes no electricity itself, and a pinwheel is a simple one.
- Pinwheels, the windmills on old farms and the tall wind machines on hilltops work in much the same way as the turbine in a dam.
- A turbine is a wheel of angled blades that is pushed around and around by moving water, steam or wind.
- A turbine is a turning machine, which means it is a machine whose main job is turning around, the way a pinwheel turns when wind blows.
Paragraph 3 says a generator makes electricity because of its magnets and coils of wire. Which detail for [8] shows Noah how they make it?
- The generator sends out a steady electric current, which leaves the powerhouse through thick cables and heads toward the power lines nearby.
- The magnets and the copper wire inside the generator are the two parts that, working together inside the powerhouse, are responsible for producing the electricity.
- The harder and faster the water strikes the turbine blades, the faster the shaft spins and the more current the dam can produce.
- As the shaft turns, large magnets sweep past coils of copper wire, and the changing magnetic field pushes electrons through the wire as a current.
Pia sees that sentence [11] cheers instead of explaining. Which version keeps a fact from the draft in an objective tone?
- A hydroelectric dam doesn't burn any fuel, so it's super clean and there's no nasty smoke to deal with.
- A hydroelectric dam burns no fuel, which makes it the most admirable choice that any sensible town could possibly make.
- A hydroelectric dam burns a small amount of coal to start its turbines, so it produces less smoke than other power plants.
- A hydroelectric dam burns no fuel, so it produces electricity without releasing smoke into the air.
Why Skin Burns in the Sun (informative draft)
[1] Sunlight feels warm on the skin, but the warmth is not what causes a sunburn, which can happen even on a cool, breezy day at the beach or on a snowy mountain. [2] The cause is ultraviolet light, which is light that is ultra and violet.
[3] Sunlight contains the visible light that people see, infrared rays that people feel as heat, and a smaller share of ultraviolet light. [4] Ultraviolet light carries more energy than visible light, and the type called UVB can damage the DNA inside the cells of the skin's outer layer. [5] Skin turns red after too much sun because the body reacts to that damage. [6] The body does something to the skin, and then the skin turns red. [7] The redness usually appears a few hours after the time in the sun and is often at its worst about a day later.
[8] Skin has its own defense, a brown pigment called melanin, which absorbs ultraviolet light before it can reach the deeper cells. [9] People with more melanin burn less easily, although anyone's skin can be damaged by enough ultraviolet light. [10] A tan is a sign that the skin has started making extra melanin after it has already been exposed.
[11] Clouds block much of the sun's warmth but let a large share of its ultraviolet light through, so people can burn on gray days. [12] Snow, sand and water also reflect ultraviolet light back up toward the skin. [13] Sunscreen is totally the greatest thing ever, and anyone who skips it is being kind of silly. [14] Shade, wide hats and clothing that covers the arms and legs block ultraviolet light as well.
Paragraph 2 says skin turns red because the body reacts to damage. Tala needs a detail for [6]. Which detail shows how the reaction makes skin red?
- The body's own reaction to the damaged cells, rather than the heat of the sun, is the real reason that burned skin turns red.
- Hot weather can also make a face look red, because the body widens the vessels near the skin to give off heat.
- Damaged cells send out chemical signals that widen the tiny vessels just under the surface, and the extra flow through them makes the skin look red and feel hot.
- After a long afternoon in strong sun, the skin on the shoulders, the cheeks and the nose turns pink and then a deeper and deeper shade of red by the end of the day.
Zee sees that sentence [13] sounds like a chat, not an essay. Which version keeps the point in an objective tone?
- Sunscreen blocks the sun's warmth before it reaches the skin, which keeps the skin cool and lowers the chance of a burn.
- Sunscreen absorbs or reflects much of the ultraviolet light, and people who forget to wear it are careless and should know better.
- Sunscreen absorbs or reflects much of the ultraviolet light before it reaches the skin, which lowers the chance of a burn.
- Sunscreen soaks up a bunch of the UV before it hits you, so you're way less likely to get totally fried.
