7Th Grade Science Flexible Learning Lessons

Smith-Cotton Junior High 7th Grade Science

Flexible Learning Lessons

Lesson - 41 Directions: Read and answer the following:

Imagine an eleven-year-old boy named Paul. Now imagine Paul inside a wood cabin. He is shivering. It is cold outside, and inside the cabin it isn’t much warmer. Paul can hear the rain beating down on the roof. Every few minutes there would be a loud boom, and thunder would shake the cabin walls. Paul is happy to be inside the cabin, safe and dry with his family. “Let’s make this cabin warmer,” says his father. “Paul, help me build a fire.” Paul fetches the firewood and then watches as his father carefully stacks the logs in the shape of a pyramid. Paul’s father puts several small sticks of kindling in the bottom of the pyramid. The kindling would catch on fire much more quickly than the big logs. Paul’s father lights a match, and soon the logs crackle and burn in the fireplace, shooting off small sparks. The fire gives off some light, but it also gives off heat. Within 30 minutes the inside of the cabin is warm and toasty. Thanks to the radiation of heat from the fire, Paul isn’t shivering any more.

Though all that Paul’s father did was light a match to start the fire, there was a complex set of interactions that had to occur for the fire to ignite and grow. There are three components needed for a fire to successfully burn: fuel, oxygen and a heat source. The matches were the heat source and the logs were the fuel. The oxygen supply came from the air around the fireplace. That’s why Paul’s father had to pile up the logs as a pyramid, with space in between them. If the logs had been too close together, there wouldn’t have been enough oxygen for the fire and it could have fizzled out. A wood fire can grow very quickly. That’s why it’s so important to be careful when lighting fires and to never leave them unsupervised. A wood fire, like the one in Paul’s fireplace, can reach temperatures over 1,000 degrees Fahrenheit. The hottest part of the fire is often the red glowing embers that are left in the fireplace once the wood has burned through. These embers can be as hot as 1,200-1,500 degrees Fahrenheit. Though fire is a common heat source, heat can come from many different sources. Heat can also be transferred from one object to another in a variety of ways.

Scientists use the term “heat” to refer to the energy transferred when two objects or systems are at different temperatures. Heat naturally moves from warmer areas to cooler areas. Think of what happens if you leave a bowl of ice cream out in hot weather. At first, the ice cream is much cooler than the air around it. But if you go back in an hour, the ice cream has melted, and it is roughly the same temperature as the surrounding air. The heat from the air has moved to the ice cream. In this example, the air is the heat source, the place where the higher temperature is found. The ice cream is the heat sink, or the place to which the heat moves. Whenever there is a temperature difference in a system or a group of objects, the heat will naturally move from the heat source to the heat sink.

How does heat transfer from one object to another?

Heat transfers in three different ways: conduction, convection, and radiation. Conduction is the transfer of heat between two surfaces that are directly in contact with one another. When you burn yourself on a hot pan while making scrambled eggs, that’s an example of conduction. The heat is transferring from a very hot surface (the frying pan) to a cooler surface (your hand). Heat transfers through some materials better than others. Metals are especially good thermal conductors; that’s why pots and pans are made out of metal. Materials that are very slow to transfer heat are called thermal insulators. Some examples of materials that are thermal insulators include rubber and cork. Typically materials that are good thermal conductors – like gold, silver and copper – are also good conductors of electricity.

The second way that heat can transfer is through convection. Convection is the transfer of heat through the movement of large amounts of a liquid or gas. An example of this is the storm outside Paul’s cabin. Thunder and lightning are caused when a large mass of hot air meets a large mass of cool air. Warm air tends to rise, and cool air tends to fall. The movement of these air masses and the transfer of energy that occurs are called convection.

The third way heat transfer can occur is through a process called radiation. Radiation is when there is no material transferring the heat. Instead, the energy is carried by electromagnetic waves. Electromagnetic waves come in a wide variety of types: they can be infrared, visible light, UV, or radio waves. The hotter that the object is, the more infrared radiation (and heat) it gives off. The fire that Paul is looking at is radiating heat into the rest of the cabin.

Another example of heat radiation is the sun. At the sun’s core the temperature is at least 10 million Kelvin, and on the surface of the sun, the temperature is about 6,000 Kelvin. Kelvin is a form of measurement of heat that scientists use, instead of measuring degrees in Fahrenheit or Celsius. What does 10 million Kelvin actually feel like? It’s about 30,000 times as hot as boiling water. All of that heat travels from the sun to the earth on electromagnetic waves. To reach the earth’s surface, the waves must travel through 93 million miles of our solar system. When the radiation arrives from the sun to the earth, it causes the ground to heat up. An object that is especially good at radiating heat is called a blackbody. The sun is a perfect example of a blackbody.

The earth is also a blackbody – it doesn’t just absorb heat from the sun’s electromagnetic waves; the earth also radiates heat out into space. Some of the heat that the earth radiates is the same energy from the sun. Around 30% of the electromagnetic waves that arrive from the sun are bounced back into outer space by the earth. The rest of the electromagnetic energy is either absorbed by the earth’s atmosphere or heats the surface and oceans of the earth.

Questions:

1. What do Paul and his father build in the cabin?

A. a radio B. a clock C. an engine D. a fire

2. What does this text explain?

A. This text explains what a wood cabin is and how to build one. B. This text explains what heat is and how it moves from one object to another. C. This text explains what UV radiation is and why it can be harmful to people. D. This text explains what oxygen is and how the human body uses it to survive.

3. Heat moves from warmer areas to cooler areas.

What evidence from the text supports this statement?

A. Heat moves from the hot fire Paul and his father build to the cold air of the cabin. B. A wood fire can reach temperatures of more than 1,000 degrees Fahrenheit. C. After Paul fetches firewood, his father carefully stacks it in the shape of a pyramid. D. Ten million Kelvin is a temperature about 30,000 times as hot as boiling water.

4. What is an example of a heat source?

A. rubber B. oxygen C. thunder D. the sun

5. What is this text mainly about?

A. a wood cabin B. convection C. heat D. the relationship between a boy and his father

Lesson - 42 Directions: Read and answer the following

When you’re thirsty, few things feel better than drinking a tall glass of water poured over ice. But as you’re drinking, do you realize you are experiencing two very different forms of water, and that each form can be used for totally different jobs?

If you suddenly catch a cold, your parent may give you a cup of steaming hot tea to drink. That steam is a third form of water and has its own properties.

Water is the most common compound on Earth, covering about 70 percent of the planet’s surface. Most of that water is in liquid form, sloshing around in the oceans and other bodies of water. Because it’s so common, and because it’s easy to use for so many different purposes, liquid water is part of our everyday lives. We use water to nourish everything from ourselves to our pets to our yards. Like all liquids, water travels faster and increases in pressure as more of it is pressed through a tighter space. We can see this principle after we brush our teeth, using water flowing from the tap to push the toothpaste down the drain. By increasing the pressure, we use water to clean glasses in a dishwasher and cars in a carwash.

Water is great at cooling things down. To cool off our bodies, we go swimming at the pool on a hot summer day. To cool off our cars and factories, we force water through pipes to keep engines from overheating.

Water can also be a great way to travel. People have used sails, paddles and oars to propel boats through water for thousands of years. In modern times, one gallon of diesel fuel can pull one ton of cargo 59 miles by truck down a highway, 202 miles by train down a railroad track, and 514 miles in a boat through water.

Another traditional use for water is generating power. When water drops quickly in elevation, as over a waterfall, special gears called turbines can be placed inside the stream. Turbines can be used either directly to spin machines like sewing looms, or indirectly to capture that momentum as electricity. America has used this property of falling water to build giant electricity plants, including the ones at Hoover Dam and Niagara Falls.

When water freezes into ice, it becomes hard. Unlike most other frozen liquids, ice is actually less dense than water in its liquid form, which is why ice cubes float. These two properties explain the Antarctic ice pier, which has been constructed at America’s McMurdo research station every summer since 1973. Workers pump seawater into a contained area and let it freeze. The pier becomes so sturdy it can support semi-trucks, which transport tons of food and equipment from supply ships to the station. Ice also cools things down. The National Seal Sanctuary in Britain uses a machine to produce ice for the sea lions, because they fight less when they’re cool. Zoos around the world buy ice machines to chill areas for polar bears and penguins. Humans like ice so much that large restaurants and hotels often spend more than $10,000 on a single ice machine.

As the temperature rises, ice melts into water, which boils into steam. Perhaps the most common use of steam is electricity; about 90 percent of all electricity generated in the U.S. comes from steam turbines. Heat to boil the water is generated by many fuels, including coal, natural gas and nuclear fuel.

For thousands of years farmers have used steam to sterilize their fields and kill weeds and bacteria. You can see steam at work in many buildings and homes, where it is forced through pipes and radiators for heat. You can also see steam at work if your parents cook vegetables in a steamer.

Because we are constantly surrounded by water, ice and steam, it’s easy not to pay attention to them. But all three are really just the same chemical compound that makes life on Earth possible.

Questions:

1. What are the three forms of water discussed in the passage?

A. liquid water, steam, and pressure B. steam, electricity, and liquid water C. ice, liquid water, and steam D. ice, steam, and pressure

2. What does the passage describe?

A. The passage describes different forms and uses of water. B. The passage describes different kinds of weeds that grow in fields. C. The passage describes how to cook vegetables using a steamer. D. The passage describes the effects of brushing your teeth. 3. Water is used for many different things.

What evidence from the passage supports this statement?

A. Seals are more likely to fight when they are hot than when they are cool. B. As the temperature rises, ice melts into water, and water boils into steam. C. If you catch a cold, you may be given a cup of hot tea to drink. D. Water is used for cooling down engines, generating power, and traveling.

4. What is one difference between ice and steam?

A. Ice is hot; steam is cold. B. Ice is cold; steam is hot. C. Ice is liquid; steam is solid. D. Ice is a gas; steam is liquid.

5. What is this passage mainly about?

A. the National Seal Sanctuary in Britain B. the uses of water, ice, and steam C. an ice pier at America’s McMurdo research station D. how water can be used to generate electricity

Lesson - 43

Directions: Read and answer the following

When light strikes an object, some of it penetrates the object, and some of it is reflected and reaches your eye. When an object is wet, more light penetrates the object, so less light is reflected. As a result, less light reaches your eye and so the wet object looks darker. Read on for a more detailed explanation.

Fact 1. When light moves from air to water, some of the light reflects and some refracts. The reflected light "bounces" off the water, and the refracted light bends at the air/water boundary and passes through the water.

Fact 2. When light strikes any object, some of the light is reflected and some is refracted and transmitted through or absorbed by the object. The relative amounts of which depend on the material properties of the object, its index of refraction.

Fact 3. When a material gets wet and absorbs water, the material's index of refraction is effectively changed, making it so that more light penetrates and less light is reflected.

The light that is reflected from an object is the light that we perceive. How light or dark an object appears depends on how much light that strikes an object reflects back to our eye. For an object whose material has an index of refraction close to that of air very little light is reflected. For an object whose material has an index of refraction different than air, most of the light that strikes it is reflected.

When an object gets wet and absorbs water, its index of refraction effectively moves closer to that of air. When light strikes a wet object, therefore, less light is reflected than when it is dry. A pair of wet pants, a wet sidewalk, and a wet beach, therefore, reflects less light, and therefore looks darker. Steel, glass or plastic doesn't look darker when it is wet because it doesn't absorb any water, and therefore the same amount of light is reflected whether it is dry or wet.

Questions:

1. When light strikes an object, what happens to some of the light?

A. Some of the light turns into sound. B. Some of the light becomes brighter. C. Some of the light is reflected. D. Some of the light becomes less bright. 2. What is an effect of an object getting wet?

A. More light is reflected by the object. B. Less light penetrates the object. C. More light penetrates the object. D. The object looks lighter.

3. Read Fact 1 and look at the image next to it.

When light moves from air to water, some of the light reflects and some refracts. The reflected light 'bounces' off the water, and the refracted light bends at the air/water boundary and passes through the water.

Based on this information, what can you conclude about the image next to Fact 1?

A. The image shows light being refracted but not reflected by water. B. The image shows light being reflected but not refracted by water. C. The image shows light being reflected and refracted by water. D. The image shows light striking water from different directions.

4. Read Fact 2 and look at the image next to it.

When light strikes any object, some of the light is reflected and some is refracted and transmitted through or absorbed by the object. The relative amounts of which depend on the material properties of the object, its index of refraction. Based on this information and the image next to it, what is a difference between jeans and a mirror?

A. Jeans refract less light than a mirror does. B. Jeans absorb less light than a mirror does. C. Jeans refract more light than a mirror does. D. Jeans reflect more light than a mirror does.

5. What is the main idea of this text?

A. Steel, glass, and plastic do not look darker when they are wet. ct. B. If an object is wet, it reflects less light and looks darker. C. When light strikes an object, some of it is reflected by the object. D. When light strikes an object, some of it penetrates the object.

Lesson - 44

Directions: Read and answer the following

Maria gripped the handles of the airplane seat and squeezed her eyes shut. Engines fired up one by one, and the inside of the cabin soon filled with their powerful roar. Maria had put in earplugs to block out the noise, but some of it crept in anyway. She could sense the plane preparing for takeoff. Her mother, who sat next to her, reached out to stroke her hand, but she shook off this comforting touch. Maria did not want anyone, not even her own mother, to know just how terrified she was. Across the aisle, her older brother Luis sat with his arms loose and relaxed in his lap. He chatted with their father about the hot springs and majestic mountains they were going to see in Montana, where they were headed on vacation. Luis showed no signs of fear. Maria felt a sharp pang of jealousy at her brother’s courage.

Wheels turned with greater and greater speed. Wind rushed over the frame of the plane and added to the deafening noise. Suddenly, with a jolt that made her stomach lurch, they were in the air. Beads of cold sweat trickled down Maria’s neck. All she wanted was to be back on solid ground. She hated the idea of being trapped in a flimsy aluminum and plastic tube, hurtling at 500 miles an hour through the skies. Every time she had flown on an airplane in the past, she had remained frozen in her seat for the entire flight, trembling and praying for a safe landing. This time, on her fourth trip, she had promised herself she would overcome this crippling fear. Instead of pulling down the window shade next to her, as she always did, she kept it open. Now she peered out the window cautiously, and couldn’t help but marvel at the receding landscape of New York City below her: the neat rows of apartment buildings, trees and skyscrapers that now seemed small enough to pluck with her fingers. Puffy white clouds drew closer and soon moved right through the airplane wing. Then Maria noticed the wing flapping like a fragile leaf in a strong gust of wind. She closed her eyes again.

“We have now reached cruising altitude,” said the pilot. “You may remove your seatbelts.” Maria stayed put but ventured another glance out the window. It had been raining all night but seemed as though the sun would shine today. The sky now appeared as a beguiling mix of dark rainclouds and bright yellow light and little pockets of sky blue. Maria gazed in wonder at this close-up view of the skies. After a few moments, she saw what seemed to be a rainbow poking out of a cloud. As the plane moved along she could see it more clearly. It was the most beautiful rainbow she had ever seen. Its colors were vibrant and sharp, and it was in the shape of a full circle instead of the usual semicircle. For a minute she thought she was imagining this magnificent rainbow, but it did not go away when she blinked her eyes a few times. Forgetting her fears altogether, she exclaimed, “Look, Luis! Mom! Dad! A rainbow!” Luis and her parents got out of their seats and huddled around her window to take a look.

“I have never seen anything like it in my forty-two years on this planet!” said her father. “A circular rainbow!”

“Well spotted, Maria!” said her mother.

Luis looked at her with a bit of envy for having made such an interesting discovery. But eventually, he too complimented Maria for finding the rainbow. “Very cool,” he said, appreciating the sight.

Everyone else on the plane started to wonder what the buzz was about, and soon other passengers and even flight attendants wandered over to Maria’s side of the plane to gaze at the unusual rainbow. Maria’s fears of flying seemed to have vanished. She snapped off her seatbelt and stood up. “Does anybody know why it is a full circle?” she asked. “And why does a rainbow even appear? I’ve never quite understood it.” A slim young woman wearing wire-rimmed glasses happened to be sitting behind Maria. “That’s a very good question, young lady,” she said. “I’m Laura,” she said, holding out her hand. “I’m a physicist, and I study the way light travels from stars like the sun. Would you like me to explain to you a bit more about rainbows?”

“Yes,” said Maria, nodding excitedly. She had just finished snapping pictures of the rainbow with her smartphone. “I know it has something to do with the way sunlight hits water particles in the air, right?”

“Yes,” said Laura, “That’s exactly right. You only get a rainbow when sunlight hits fine particles of water—mist or fog, or even falling raindrops. Normally we only see sunlight as bright white or yellow in color, but when a ray of sunlight hits a water droplet suspended in the air, the sunray bends its path, bouncing off the water droplet in a completely different direction. As it bounces off, the sunray gets split up into all the different wavelengths of light that it is composed of: red, orange, yellow, green, blue, indigo, and violet. That’s when we see a rainbow.”

“Interesting,” said Maria. “But why doesn’t sunlight form rainbows when it hits other particles, like human bodies for instance?”

“Because sunlight, like all light, normally travels in straight lines, even when it comes into contact with other substances like human flesh, or a tree, or a piece of wood. Only when it hits water or some other transparent material, like glass, does the sunray bend. And only when it hits water does it bend in such a way that it gets broken up into all of its wavelengths of color, forming a rainbow.”

Maria stared at Laura in awe. It was amazing that she knew how to explain the science behind that beautiful sight out the window. A group of people now huddled around Laura as she explained things.

“What I really want to know is,” said Luis. “Why this rainbow is a circle? Can we get to that part now?”

“Yes, of course,” said Laura, with a twinkle in her eye. “That’s easy to explain. Normally we view rainbows from the ground, and the surface of the earth breaks up the rainbow and stops us from seeing it as a whole. From high up in the air we can see the full effect because there is no land mass blocking off the other half of it. Maria was very, very lucky to have spotted a rainbow from an airplane window. It’s rare to see a full circle rainbow, and we might not have another chance for the rest of our lives. She’s made this a flight to remember for all of us.” Everyone on the plane erupted into applause. “Well done, young lady!” said an old man, patting her on the back before pulling out his camera to take photos.

After a few more minutes the rainbow drifted out of view, but the joy of discovering it stayed with Maria for the rest of her flight. Now she would have a great story to tell her friends when she got home. Even when the plane hit a patch of turbulence and jolted around a bit in the air, Maria did not feel as afraid as she had before. She now appreciated that the airplane was a marvelous invention that had allowed her to see something rare and beautiful, something that she would never have seen on solid ground. When the plane touched down in Montana, she knew that thanks to the special rainbow she had been so lucky to see, she had solved her fears of flying.

1. Where does this story take place?

A. Montana B. New York City C. on an airplane D. in a helicopter

2. What main problem does Maria face?

A. She does not want to go on vacation. B. She is afraid of flying. C. She does not like her brother. D. She has never seen a rainbow.

3. What is this passage mostly about?

A. Maria’s family vacation to Montana B. the beautiful mountains and hot springs of Montana C. how a rainbow helps Maria overcome her fear of flying D. the scientific study of light waves

4. Choose the answer that best completes the sentence below.

Rainbows are usually shaped like a semicircle, ______the rainbow Maria saw in the sky was a full circle.

A. thus B. also C. finally D. but

5. How are rainbows formed?