A spaceship with some astronauts is orbiting the moon. The astronauts see an asteroid crashing onto the surface of the moon. why is it that they cannot hear the explosion caused by the crashing of the asteroid?

the sound waves are unable to travel from the moon's surface to the spaceships.

all the sound waves are absorbed by the surfaced of the moon.

the sound waves are reflected from the surface of the spaceship.

all the sound waves are absorbed by the surface of the spaceship.

which of the following correctly describes the two factors that affect the speed of sound in air?

temperature and humidity of the air

temperature and volume of the air

Lead has the density of 11.3g/cm3 , and 1200 m/s speed of sound; Iron has the density of 7.87 g/cm3 ,5000m/s speed of sound ; Oxygen has the density of 0.00143 g/cm3, 320 m/s speed of sound ; ; Air has the density of 0.00129g/cm3, 330 m/s speed of sound. Which of the following information's correctly describes the speed of sound?

The speed of sound is greater in metals than in gases.

the denser the metal, the greater the speed of sound

as the density of the substance decreases, the speed of sound decreases too.

the speed of sound increases as the density of the substance increases.

Why is sound able to travel faster through a solid than a gas?

Solid molecules are packed tightly.

Sound does not travel faster through a solid than a gas.

Gas molecules are packed tightly

How does sound produce?

Sound is produced through vibrating objects.

Sound is produced through creating waves in the object

Sound is produce through motion of particles.

Why does during hotter days, sound seem to be heard faster?

Molecules at higher temperatures have more energy, thus they can vibrate faster.

Molecules at higher temperatures have more energy, thus they can vibrate slower.

Molecules at higher temperatures have less energy, thus they can vibrate more.

Molecules at higher temperatures have less energy, thus they can vibrate faster.

Effect of temperature to the speed of sound

Investigates the effect of temperature to the speed of sound

Investigates the effect of temperature to speed of sound through fair testing;

Short Quiz in Science 8 investigates the effect of temperature to speed of sound through fair testing

air mass a large area of air that has uniform temperature, humidity, and pressure. air pressure the force that a column of air applies on the air or a surface below it albedo the measure of the sun's reflectivity on Earth's different surfaces atmosphere the layers of gases surrounding Earth climate average weather conditions in a specific region over a long period of time coriolis effect the movement of wind or currents in a curved path due to Earth's rotation eddy Smaller, temporary loops of swirling water that can travel long distances before dispersing front a boundary between two air masses greenhouse gas a gas in the atmosphere that absorbs part Earth’s outgoing infrared radiation gyre a large circular system of ocean currents. humidity the amount of water vapor in the air hydrosphere system containing all the solid and liquid water on Earth jet stream Narrow bands of high speed wind high in the troposphere that move from west to east land breeze Winds that blow at night from land toward the sea. This is due to the fact that land has a low specific heat capacity and cools faster than water. This creates high pressure over the land at night and thus wind. local winds Winds that blow over short distances polar easterlies cold winds that blow from the east to the west near the North Pole and South Pole. prevailing wind distinct wind patterns caused by differences in pressure and the Coriolis effect sea breeze Winds that blow during the day from the sea toward land. This is due to water having a high specific heat capacity and it does not heat or cool quickly. High pressure then forms over the water during the day and blows toward the land. specific heat capacity The amount of heat that must be added to a substance to increase the tempurature by one degree Celsius storm surge water that has blown outward from the center of a tropical cyclone or hurricane and creates an abnormal rise in ocean waters on the coast surface current Currents near the surface of the ocean. Driven by wind, the Coriolis effect, and continental deflection trade winds Steady winds that flow from east to west between 30°N latitude and 30°S latitude along the equator tropical cyclone a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters typhoon a tropical cyclone occurring in the Pacific Ocean; especially in the region of the Philippines or the China Sea. weather the short-term atmospheric conditions in a given place and time westerlies steady winds that flow from west to east in the middle latitudes (30- 60 Degrees). These impact our weather in the US. wind shear A large shift in wind speed and

Weathering describes the breaking down or dissolving of rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. Once a rock has been broken down, a process called erosion transports the bits of rock and mineral away. No rock on Earth is hard enough to resist the forces of weathering and erosion. Together, these processes carved landmarks such as the Grand Canyon, in the U.S. state of Arizona. This massive canyon is 446 kilometers (277 miles) long, as much as 29 kilometers (18 miles) wide, and 1,600 meters (1 mile) deep. Weathering and erosion constantly change the rocky landscape of Earth. Weathering wears away exposed surfaces over time. The length of exposure often contributes to how vulnerable a rock is to weathering. Rocks, such as lavas, that are quickly buried beneath other rocks are less vulnerable to weathering and erosion than rocks that are exposed to agents such as wind and water, As it smoothes rough, sharp rock surfaces, weathering is often the first step in the production of soils. Tiny bits of weathered minerals mix with plants, animal remains, fungi, bacteria, and other organisms. A single type of weathered rock often produces infertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil. Soils types associated with a mixture of weathered rock include glacial till, loess, and alluvial sediments. Weathering is often divided into the processes of mechanical weathering and chemical weathering. Biological weathering, in whichliving or once-living organisms contribute to weathering, can be a part of both processes. Mechanical Weathering Mechanical weathering, also called physical weathering and disaggregation, causes rocks to crumble. Water, in either liquid or solid form, is often a key agent of mechanical weathering. For instance, liquid water can seep into cracks and crevices in rock. If temperatures drop low enough, the water will freeze. When water freezes, it expands. The ice then works as a wedge. It slowly widens the cracks and splits the rock. When ice melts, liquid water performs the act of erosion by carrying away the tiny rock fragments lost in the split. This specific process (the freeze-thaw cycle) is called frost weathering or cryofracturing. Figure 4.3 Frost Wedging Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Changes in temperature cause rock to expand (with heat) and contract (with cold). As this happens over and over again. the structure of the rock weakens. Over time, it crumbles. Rocky desert landscapes are particularly vulnerable to thermal stress. The outer layer of desert rocks undergo repeated stress as the temperature changes from day Eventually, Lo outer night. layersflake off in thin sheets, a process called exfoliation. Exfoliation contributes to the formation of bornhardts, one of the most dramatic features in landscapes formed by weathering and erosion. Bornhardts are tall, domed, isolated rocks often found areas. in tropical Sugarloaf Mountain, an iconic landmark in Rio de Janeiro, Brazil, is bornhardt. a Salt also works to weather rock in a process called haloclasty. Saltwater sometimes gets into the cracks and pores of rock. If the saltwater evaporates, salt crystals are left behind. As the crystals grow, they put pressure on the rock, slowly breaking it apart. Plants and animals can be agents of mechanical weathering. The seed of a tree may sprout in soil that has collected in a cracked rock. As the roots grow, they widen the cracks, eventually breaking the rock into pieces. Over time, trees can break apart even large rocks. Even small plants, such as mosses, can enlarge tiny cracks as they grow. Animals that tunnel underground, such as moles and prairie dogs, also work to break apart rock and soil. Other animals dig and trample rock aboveground, causing rock to slowly crumble. Chemical Weathering Chemical weathering changes the molecular structure of rocks and soil.For instance, carbon dioxide from the air or soil sometimes combines with water in a process called carbonation. This produces a weak acid, called carbonic acid, that can dissolve rock. Carbonic acid is especially effective at dissolving limestone. When carbonic acid seeps through limestone underground, it can open up huge cracks or hollow out vast networks of caves. Carlsbad Caverns National Park, in the U.S. state of New Mexico, includes more than 119 limestone caves created by weathering and erosion. The largest is called the Big Room.. With an area of about 33,210 square meters (357,469 square feet), the Big Room is the size of six football fields. Another type of chemical weathering works on rocks that contain iron. These rocks turn to rust in a process called oxidation. Rust is a compound created by the interaction of oxygen and iron in the presence of water. As rust expands, it weakens rock and helps break it apart. Another familiar form of chemical weathering is hydrolysis. In the process of hydrolysis, a new solution (a mixture of two or more substances) is formed as chemicals in rock interact with water. In many rocks, for example, sodium minerals interact with water to form a saltwater solution. Hydration and hydrolysis contribute to flared slopes, another dramatic example of a landscape formed by weathering and erosion. Flared slopes are sometimes nicknamed "wave rocks." Their c-shape is largely concave rock formations a result of subsurface weathering, in which hydration and hydrolysis wear away rocks beneath the landscape's surfaceWeathering and People Weathering is a natural process, but human activities can speed it up. For example, certain kinds of air pollution increase the rate of weathering Burning coal, natural and petroleum releases chemicals such as nitrogen oxide and gas, sulfur dioxide into the atmosphere. When these chemicals combine with sunlight and moisture, they change into acids. They then fall back to Earth as acid rain. Acid rain rapidly weathers limestone, marble, and other kinds of stone. The effects of acid rain can often be seen on gravestones, making names and other inscriptions impossible to read. Acid rain has also damaged many historic buildings and monuments. For example, at 71 meters (233 feet) tall, the Leshan Giant Buddha at Mount Emei, China is the world's largest statue of the Buddha. It was carved 1,300 years ago and sat unharmed for centuries. An innovative drainage system mitigates the natural process of erosion But in recent years, acid rain has turned the statue's nose black and made some of its hair crumble and fall.

Standard 7.PS1.3 -Develop a model to explain how changes to a system can be explained by changes in temperature and/or pressure and the effect of those changes on particle motion and/or spatial arrangement.

What is the page mainly about? (Answer: C — Homes meet a basic need) A) House colors B) Old buildings C) Homes meet a basic need ✓ D) Travel What basic need do homes give? (Answer: B — Shelter) A) Food B) Shelter ✓ C) Clothes D) Money What does “basic need” mean here? (Answer: C — Something people must have to live) A) Something nice to have B) A school rule C) Something people must have to live ✓ D) A weekend plan Homes keep people ______ and ______. What are the two words from the page? (Answer: B — dry / safe) A) rich / tall B) dry / safe ✓ C) loud / fast D) clean / funny What else are homes for, according to the text? (Answer: B — Eating, sleeping, and being with family and friends) A) Shopping B) Eating, sleeping, and being with family and friends ✓ C) Driving D) Fighting What does the heading “Meeting our needs” tell you? (Answer: B — explains how homes fit the local climate) A) A joke is coming B) This part explains how homes fit the local climate ✓ C) It is a story D) It lists prices What does “climate” mean on this page? (Answer: C — the usual weather of a place) A) Yesterday’s forecast B) A big storm C) The usual weather of a place ✓ D) Room temperature Which roof is best for cold, snowy places? (Answer: D — Slanted) A) Flat B) Dome C) Glass D) Slanted ✓ Why is a slanted roof helpful in snowy places? (Answer: B — snow slides off more easily) A) It is cheaper B) Snow slides off more easily ✓ C) Birds like it D) It is quieter Why do many houses in hot places have many windows? (Answer: B — to let air move through and keep people cool) A) To block all light B) To let air move through and keep people cool ✓ C) To make walls heavy D) To reduce street noise Which detail best supports “climate changes home design”? (Answer: C — Hot → many windows; Snowy → slanted roofs) A) People like blue walls B) Kitchens are big C) Hot → many windows; Snowy → slanted roofs ✓ D) Cities are crowded What does the caption about a traditional Japanese house show? (Answer: C — People sit on mats on the floor to eat) A) People eat outdoors B) Families don’t eat together C) People sit on mats on the floor to eat ✓ D) People stand to eat Which sentence is LEAST connected to the main idea of the page? (Answer: D — Blue walls are relaxing) A) Homes protect people from weather B) Roofs can change with climate C) Windows help rooms stay cool D) Blue walls are relaxing ✓ Which text structure organizes the right paragraph? (Answer: C — Cause–effect) A) Timeline B) Problem–solution C) Cause–effect ✓ D) Description only What is the author’s purpose? (Answer: B — to explain how homes meet a human need) A) To sell houses B) To explain how homes meet a human need ✓ C) To tell a funny story D) To give building laws What can you guess about a flat roof in a snowy place? (Answer: B — snow can pile up and be unsafe) A) Best choice B) Snow can pile up and be unsafe ✓ C) Always cheaper D) Warmer in summer Which page feature helps you find ideas quickly? (Answer: C — Headings and photo captions) A) Rhyme B) Dialogue C) Headings and photo captions ✓ D) Footnotes Which sentence is the best summary of the page? (Answer: C — Homes give shelter; designs change with climate) A) Houses are beautiful in winter B) People prefer bright colors C) Homes give shelter; designs change with climate (slanted roofs, many windows) ✓ D) Windows are the most important part True/False or Short Answer (5) True/False: All homes have the same purpose, even if they look different. (Answer: True) True/False: In hot places, houses usually have fewer windows to keep heat in. (Answer: False — hot places → many windows for airflow/cooling) Short Answer (1–3 words): Homes provide shelter to keep people _____ and _____. (Answer: dry; safe) Short Answer (one example): Write one climate → design pair from the page. (Answer: cold/snowy → slanted roof OR hot → many windows) True/False: The photo shows people in Japan eating on mats on the floor. (Answer: True)

Lipids are large, nonpolar organic molecules. They do not dissolve in water. Lipids include triglycerides (trie-GLIS-uhr-IEDZ), phospho- lipids, steroids, waxes, and pigments. Lipid molecules have a higher ratio of carbon and hydrogen atoms to oxygen atoms than carbohydrates have. Because lipid molecules have larger numbers of carbon-hydrogen bonds per gram than other organic com- pounds do, they store more energy per gram. Fatty Acids Fatty acids are unbranched carbon chains that make up most lipids. Figure 3-10 shows that a fatty acid contains a long carbon chain (from 12 to 28 carbons) with a carboxyl group, —COOH, attached at one end. The two ends of the fatty-acid molecule have different properties. The carboxyl end is polar and is thus hydrophilic or attracted to water molecules. In contrast, the hydro- carbon end of the fatty-acid molecule is nonpolar. This end tends not to interact with water molecules and is said to be hydrophobic (HIE-droh-FOH-bik), or “water fearing.” In saturated fatty acids, such as palmitic acid, which is shown in Figure 3-10, each carbon atom is covalently bonded to four atoms. The carbon atoms are in effect full, or saturated. In contrast, linoleic acid, also shown in Figure 3-10, has carbon atoms that are not bonded to the maximum number of atoms to which they can bond. Instead, they have formed double bonds within the carbon chain. This type of fatty acid is said to be unsaturated. Triglycerides Three classes of lipids important to living things contain fatty acids: triglycerides (fats), phospholipids, and waxes. A triglyceride is composed of three molecules of fatty acid joined to one molecule of the alcohol glycerol. Saturated triglycerides are composed of saturated fatty acids. They typically have high melting points and tend to be hard at room temperature. Common dietary saturated triglycerides include butter and fats in red meat. In contrast, unsaturated triglycerides are composed of unsaturated fatty acids and are usually soft or liquid at room temperature. Unsaturated triglycerides are found primarily in plant seeds where they serve as an energy and carbon source for germinating plants. Phospholipids Phospholipids have two, rather than three, fatty acids attached to a molecule of glycerol. They have a phosphate group attached to the third carbon of the glycerol. As shown in Figure 3-11, the cell membrane is made of two layers of phospholipids, called the lipid bilayer. The inability of lipids to dissolve in water allows the mem- brane to form a barrier between the inside and outside of the cell. Hydrophilic “head” Phospholipids Hydrophobic “tail” Phospholipids Water Water The lipid bilayer of a cell membrane is a double row of phospholipids.The “tails” face each other.The “head” of a phospholipid, which contains a phosphate group, is polar and hydrophilic.The two tails are two fatty acids and are nonpolar and hydrophobic. FIGURE 3-11 H C H C O OH H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H C H H H H C H H C H H C H H C H H C H C O OH H C H H C H H C H C H C H C H H C H H C H C H H C H H C H C H H H H C H Fatty acids have a polar carboxyl head, highlighted in purple, and a nonpolar hydrocarbon tail, highlighted in green. FIGURE 3-10 Palmitic acid Linoleic acid mb06se_bchs02.qxd 5/18/07 10:49 AM Page 59 60 CHAPTER 3 1. Compare the structure of monosaccharides, dis- accharides, and polysaccharides. 2. How are proteins constructed from amino acids? 3. How do amino acids differ from one another? 4. Describe a model of enzyme action. 5. Why do phospholipids orient in a bilayer when in a watery environment, such as a cell? 6. Describe how the three major types of lipids differ in structure from one another. 7. What are the functions of the two types of nucleic acids? CRITICAL THINKING 8. Applying Information Before a long race, run- ners often “carbo load.” This means that they eat substantial quantities of carbohydrates. How might this help their performance? 9. Recognizing Relationships High temperatures can weaken bonds within a protein molecule. How might this explain the effects of using a hot curling iron or rollers in one’s hair? 10. Applying Information You want to eat more unsaturated than saturated fats. Name examples of foods you would eat more of and less of. SECTION 2 REVIEW Waxes A wax is a type of structural lipid consisting of a long fatty-acid chain joined to a long alcohol chain. Waxes are waterproof, and in plants, form a protective coating on the outer surfaces. Waxes also form protective layers in animals. For example, earwax helps pre- vent microorganisms from entering the ear canal. Steroids Unlike most other lipids, which are composed of fatty acids, steroid molecules are composed of four fused carbon rings with various functional groups attached to them. Many animal hor- mones, such as the male hormone testosterone, are steroid com- pounds. One of the most familiar steroids in humans is cholesterol. Cholesterol is needed by the body for nerve and other cells to func- tion normally. It is also a component of the cell membrane. NUCLEIC ACIDS Nucleic acids are very large and complex organic molecules that store and transfer important information in the cell. There are two major types of nucleic acids: deoxyribonucleic acid and ribonucleic acid. Deoxyribonucleic acid, or DNA, contains information that deter- mines the characteristics of an organism and directs its cell activi- ties. Ribonucleic (RIE-boh-noo-KLEE-ik) acid, or RNA, stores and transfers information from DNA that is essential for the manufactur- ing of proteins. Some RNA molecules can also act as enzymes. Both DNA and RNA are polymers, composed of thousands of linked monomers called nucleotides (NOO-klee-uh-TIEDS). As shown in Figure 3- 12, each nucleotide is made of three main components: a phosphate group, a five-carbon sugar, and a ring-shaped nitrogenous base.

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