Log inSign up for FREE
Library

ACAP Grade 6 ELA

Last updated about 1 year ago
15 questions

A Quick Guide to Snow and Snowflakes


Are there days when you wish for snow? If you live in a warm, dry place like one of the Arizona deserts, snow almost never falls. Florida, on the other hand, has plenty of moisture, but the temperatures are often not low enough for snow to form. Snow requires two things: moisture and low temperatures. Snow crystals cannot form without both of these.

What is snow?
Snow is precipitation in the form of ice crystals. Ice crystals form in a cloud when the temperature in the cloud is below freezing. Freezing occurs at 32 degrees Fahrenheit. Water droplets form when water changes from a vapor to a liquid. The tiny water droplets then freeze into ice crystals. When the Sun heats the water in lakes or streams, the water evaporates—or turns into vapor. This vapor rises into the atmosphere, condenses, and forms clouds. If the atmosphere is warm, rain falls from the clouds. If the atmosphere is cold (below freezing), snow falls.

What are snow crystals?
Scientists use the terms “snow crystal” and “snowflake” to describe two different things. A snow crystal is a single crystal of ice, but a snowflake is a cluster of snow crystals that falls to Earth. Snow crystals are very different from sleet.

Sleet occurs when drops of rain freeze as they fall to Earth. Snow crystals, on the other hand, are formed in a cloud before they fall to Earth.

Dr. Kenneth Libbrecht, a physics professor at the California Institute of Technology, studies snow crystals. He puts them under high-powered microscopes and photographs them. He says that the most basic form of a snow crystal is a hexagonal prism (figure 1). Some are long and thin. Others are short and thick. The size varies, but the shape remains the same. Small snow crystals usually take the simple form of a hexagonal prism.


As snow crystals grow, branches sprout from the corners to make more complicated shapes. There are six corners, so most snow crystals have six arms. The arms tend to grow at about the same rate, so they are all about the same length. Of course, not all snow crystals have a perfect shape. It is difficult to see some snow crystals with the human eye. This is a drawing of one that was photographed through a high-powered microscope (figure 2).


What are snowflakes?
Snowflakes occur when snow crystals join together. Most snowflakes are about a half an inch wide. Much larger snowflakes can form when the ground temperature is near freezing and light winds are blowing. Big snowflakes may be almost two inches wide. It is difficult to measure snowflakes, however, since they tend to melt!

Why is snow white?
Snow crystals have no color at all. When they fall as snowflakes, they appear white. Most natural materials, such as grass, dirt, or rocks, absorb some sunlight, which gives them their colors. Snow does not absorb sunlight. It reflects almost all light, so it looks white.

Sometimes deep snow will appear blue. As the light travels through many layers of snow, some of it is absorbed. Red light is absorbed more easily than blue light, so the light bouncing back tends to look blue.

Why is snow crunchy?
Snow affects how sound waves travel. When the snow is fresh and fluffy, it absorbs sound waves. Pets write about how quiet the world sounds after a snowstorm. They are making a scientific observation. New snow has a sound-dampening effect.

But as the snow is packed down, the snow crystals compress together. This creates a crunchy or creaking sound. Experts at the National Snow and Ice Data Center say that “the colder the snow, the louder the crunch.” As the snow begins to melt, it makes no noise at all.

Why study snow?
Scientists like Dr. Libbrecht study snowflakes to understand exactly how they form and assemble themselves into particular shapes. This is called self-assembly. Snowflakes use a simple form of self-assembly. The cells in our body, for example, form and divide on their own. Biological self-assembly, the kind that occurs in the human body, is much more complex than snowflake self-assembly. However, scientists often gain insight into more complex mechanisms by understanding simple ones. “There is a great deal of interesting physics, chemistry, and materials science wrapped up in snowflake growth, and studying the lowly snowflake may indeed teach us something useful,” Dr. Libbrecht says. He adds, “History has shown over and over that the fundamental knowledge gained by doing basic science (without worrying about what it’s good for) often leads to useful engineering applications.” Dr. Libbrecht does not know what those applications might be, but he thinks that scientists should try to understand how nature works because all knowledge is useful.

When people learn that he studies snowflakes, many ask, "Is every snowflake unique?"

"Yes!" he says, and then he explains. "It’s like shuffling a deck and getting the exact same shuffle for 52 cards. You could shuffle every second for the entire life of the universe, and you wouldn't come close to getting two of the same."

Each and every snowflake is amazing in its own way.
Required
1

Which sentence from the passage best supports the idea that each snowflake is an original?

Required
1

In the section "What are snow crystals?" how is the idea of the shape of snow crystals introduced?

Required
1

Which statement about snowflakes is supported by information in both the passage and figure 2?

Required
1

Which information best supports the claim that snow can appear colorful?

Required
4

The passage describes the formation of snow crystals and snowflakes. Write an essay analyzing how weather conditions affect the look and appearance of snow. Use evidence from the passage to support your response.

Required
2

A student is writing an article arguing in favor of getting rid of plastic straws. Read the introduction to the student's article.

Plastic trash makes its way into Earth's oceans, where it may have a negative impact on sea animals. A simple way to reduce the amount of plastic waste is to stop using plastic drinking straws.

Which two sentences should the student include in the introductory paragraph to best support the claim?

Required
1

Which sentence is an example of formal language that could be used in an informative essay?

Required
1

A student is writing a narrative for language arts class. Read a paragraph from the narrative.

Lanie paced backstage, waiting for her turn. She could have watched the act before her as a distraction. But she needed to run through the song in her head that she was about to perform on the piano for the school talent show. She heard the music from the violin onstage stop. Lanie knew it was now her turn.

Which sentence should the student include at the end of the paragraph to best add descriptive details?

Required
2

A student is writing a report on the importance of children eating breakfast. The student has found multiple sources. Choose the source that would most likely provide the most relevant information to answer each research question that the student wants to address in the report. Then, move that source into the correct box of the chart.

  • a web article written by a nutrition expert titled “Morning Power Recipes for Kids”
  • a website from a corporation that advertises protein bars for sale
  • a video from a television program showing foods sold at a local farmers market
  • a magazine article written by a chef titled “Delicious Desserts”
  • a government website that explains why breakfast is the most important meal of the day
  • What types of foods are best to eat for breakfast?
  • How does eating breakfast benefit school-age children?
Required
2

A student is writing a report about why the yellowhammer became Alabama's state bird. Which sources would provide the best information for the student? Move two answers into the chart.

  • an instructional guide on bird-watching in Alabama
  • a newspaper article on the official announcement of Alabama’s state bird
  • a government site listing the official state bird of each state
  • an interview with an Alabama yellowhammer expert
  • an online video about attracting yellowhammers to Alabama yards
  • a book explaining the habits and habitats of yellowhammers
  • Credible Sources for the Report
Required
2
Choose a pronoun from each drop-down menu to correctly complete the sentence.

Katie and __________ went to see that new movie, and to our surprise, __________ both really liked it.
Required
2

Which sentences correctly use an intensive pronoun? Choose two answers.

Required
1

Which sentence uses parentheses incorrectly?

Required
1

Read the sentences.

The Tuskegee Airmen were influential as the first African American men in a flying unit in the United States military. They piloted many successful missions in World War II and helped lead to the integration of the military in 1948.

What does the word influential mean as it is used in the sentences?

Required
1

Read the sentences.

The weather was changing, and the sky was growing dark. The wind blew down from the mountains, tickling the long grass and causing the flowers to dance in the breeze.

What does the phrase "tickling the long grass" mean in the sentences?