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How does snow sliding quickly down a mountain impact people
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Clothes: What do you wear when it's cold? A. Swim trunks B. Hat C. Gloves D. Sweater What do you wear when it's rainy? A. Sunglasses B. Ski suit C. Flip-flops D. Umbrella What do you wear in the summer to stay cool? A. Snowsuit B. Scarf C. Boots D. T-shirt Seasons of the Year: Which season comes after winter? A. Autumn B. Summer C. Winter D. Spring What do you like to do in the summer? A. Play hockey B. Run with sleds C. Catch snowflakes D. Swim Weather: What do you wear on a sunny day? A. Ski suit B. Neck warmer C. Gloves D. Sunglasses What happens to puddles on a warm, sunny day? A. Expand B. Turn into ice C. Dry up D. None of the above How does the sky look when it's going to rain? A. Clear B. Orange C. Cloudy D. Golden Mix: What do you wear when it's cold and snowy? A. Swimsuit B. Cowboy boots C. Ski helmet D. Winter jacket What grows on trees in the summer? A. Vegetables B. Colorful leaves C. Carrots D. Fruits What do you do when it's windy? A. Swim in a pool B. Listen to music C. Run with sleds D. Fly a kite Which of the following is a season when it's cold and snowy? A. Summer B. Spring C. Autumn D. Winter What do you wear when it's hot in the summer? A. Ski suit B. Boots C. Scarf D. Straw hat Which of the following are signs of spring? A. Leaves fall B. Snow covers the ground C. Trees lose their leaves D. Flowers bloom What clothing do you wear when it's raining? A. Gloves B. Ski suit C. Sunglasses D. Rain poncho
Amazing Antarctica The Seventh Continent. Give a globe a spin. On it you can easily find six continents. Now look at the bottom of the globe. There you will find continent number seven: Antarctica. People did not find Antarctica until about two hundred years ago. Since then, we have learned a lot about this amazing place. Antarctica is the coldest continent. It is also the continent with the strongest winds. Less rain and snow fall in Antarctica than in any other continent. Freezing Antarctica Water covers most of Earth. Almost all of it is salt water. Most of the fresh water on Earth is frozen in the ice in Antarctica. Snow does not melt during the cold summers there. The ice builds up over many years. Life on and Around Antarctica The freezing weather in Antarctica makes it a dangerous place to live. Most plants and animals can be found near the coasts or in the sea. There are no trees, but there are other plants, such as moss. Penguins and seals are some of the larger animals in the icy waters of Antarctica. A Playground for Scientists People have taken steps to make sure that scientists can study in Antarctica. Many countries send scientists to study in Antarctica. Some work there all year, even during the cold winter. Others work only in summer. Many kinds of scientists come to Antarctica. They study animals, ice, and many other things. Many kinds of scientists come to Antarctica. They study animals, ice, and many other things. Thousands of visitors also come to learn about Antarctica each year. Conclusion. People do not know a lot about Antarctica. The cold, ice, wind, and rough seas make it a difficult place to visit. However, people around the world know how important it is to protect and study Antarctica.
Write simple RCQ for A1 kids after they read: Uncle John Loves to Ski Uncle John loves to ski. In winter, he goes skiing on the snow. It's his favourite sport. What does he love to do in summer? He likes to ski too. How can he ski in summer? He goes water skiing. It's a lot of fun. Summer or winter, on snow or water, Uncle John loves to ski.
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)
A solution is a mixture in which one or more substances are uniformly distributed in another substance. Solutions can be mixtures of liquids, solids, or gases. For example, plasma, the liquid part of blood, is a very complex solution. It is composed of many types of ions and large molecules, as well as gases, that are dissolved in water. A solute (SAHL-YOOT) is a substance dissolved in the solvent. The particles that compose a solute may be ions, atoms, or molecules. The solvent is the substance in which the solute is dissolved. For example, when sugar, a solute, and water, a solvent, are mixed, a solution of sugar water results. Though the sugar dissolves in the water, neither the sugar molecules nor the water molecules are altered chemically. If the water is boiled away, the sugar molecules remain and are unchanged. Solutions can be composed of various proportions of a given solute in a given solvent. Thus, solutions can vary in concentra- tion. The concentration of a solution is the amount of solute dis- solved in a fixed amount of the solution. For example, a 2 percent saltwater solution contains 2 g of salt dissolved in enough water to make 100 mL of solution. The more solute dissolved, the greater is the concentration of the solution. A saturated solution is one in which no more solute can dissolve. Aqueous (AY-kwee-uhs) solutions—solutions in which water is the solvent—are universally important to living things. Marine microorganisms spend their lives immersed in the sea, an aqueous solution. Most nutrients that plants need are in aqueous solutions in moist soil. Body cells exist in an aqueous solution of intercellu- lar fluid and are themselves filled with fluid; in fact, most chemical reactions that occur in the body occur in aqueous solutions. Copyright © by Holt, Rinehart and Winston. All rights reserved. Liquid water Solid water Ice (solid water) is less dense than liquid water because of the structure of ice crystals. The water molecules in ice are bonded to each other in a way that creates large amounts of open space between the molecules, relative to liquid water. FIGURE 2-12 solvent from the Latin solvere, meaning “to loosen” Word Roots and Origins CHEMISTRY OF LIFE 43 ACIDS AND BASES One of the most important aspects of a living system is the degree of its acidity or alkalinity. What do we mean when we use the terms acid and base? Ionization of Water As water molecules move about, they bump into one another. Some of these collisions are strong enough to result in a chemical change: one water molecule loses a proton (a hydrogen nucleus), and the other gains this proton. This reaction really occurs in two steps. First, one molecule of water pulls apart another water molecule, or dissociates, into two ions of opposite charge: H2O ∏ H OH The OH ion is known as the hydroxide ion. The free H ion can react with another water molecule, as shown in the equation below. H H2O ∏ H3O The H3O ion is known as the hydronium ion. Acidity or alkalin- ity is a measure of the relative amounts of hydronium ions and hydroxide ions dissolved in a solution. If the number of hydronium ions in a solution equals the number of hydroxide ions, the solution is said to be neutral. Pure water contains equal numbers of hydro- nium ions and hydroxide ions and is therefore a neutral solution. Acids If the number of hydronium ions in a solution is greater than the number of hydroxide ions, the solution is an acid. For example, when hydrogen chloride gas, HCl, is dissolved in water, its mol- ecules dissociate to form hydrogen ions, H, and chloride ions, Cl, as is shown in the equation below. HCl ∏ H Cl These free hydrogen ions combine with water molecules to form hydronium ions, H3O. This aqueous solution contains many more hydronium ions than it does hydroxide ions, making it an acidic solution. Acids tend to have a sour taste; how- ever, never taste a substance to test it for acidity. In concentrated forms, they are highly corrosive to some materials, as you can see in Figure 2-13. Bases If sodium hydroxide, NaOH, a solid, is dissolved in water, it dissociates to form sodium ions, Na, and hydroxide ions, OH, as shown in the equation below. NaOH ∏ Na OH Copyright © by Holt, Rinehart and Winston. All rights reserved. Eco Connection onnection Acid Precipitation Acid precipitation, more commonly called acid rain, describes rain, snow, sleet, or fog that contains high levels of sulfuric and nitric acids. These acids form when sulfur dioxide gas, SO2, and nitrogen oxide gas, NO, react with water in the atmosphere to produce sulfuric acid, H2SO4, and nitric acid, HNO3. Acid precipitation makes soil and bodies of water, such as lakes, more acidic than normal. These high acid levels can harm plant and animal life directly. A high level of acid in a lake may kill mollusks, fish, and amphibians. Even in a lake that does not have a very elevated level of acid, acid precipitation may leach aluminum and magnesium from soils, poisoning water- dwelling species. Reducing fossil-fuel consump- tion, such as occurs in gasoline engines and coal-burning power plants, should reduce high acid levels in precipitation. Sulfur dioxide, SO2, which is produced when fossil fuels are burned, reacts with water in the atmosphere to produce acid precipitation. Acid precipitation, or acid rain, can make lakes and rivers too acidic to support life and can even corrode stone, such as the face of this statue. FIGURE 2-13 44 CHAPTER 2 This solution then contains more hydroxide ions than hydronium ions and is therefore defined as a base. The adjective alkaline refers to bases. Bases have a bitter taste; however, never taste a substance to test for alkalinity. They tend to feel slippery because the OH ions react with the oil on our skin to form a soap. In fact, commercial soap is the product of a reaction between a base and a fat. pH Scientists have developed a scale for comparing the relative con- centrations of hydronium ions and hydroxide ions in a solution. This scale is called the pH scale, and it ranges from 0 to 14, as shown in Figure 2-14. A solution with a pH of 0 is very acidic, a solution with a pH of 7 is neutral, and a solution with a pH of 14 is very basic. A solution’s pH is measured on a logarithmic scale. That is, the change of one pH unit reflects a 10-fold change in the acidity or alkalinity. For example, urine has 10 times the H3O ions at a pH of 6 than water does at a pH of 7. Vinegar, has 1,000 times more H3O ions at a pH of 3 than urine at a pH of 6, and 10,000 times more H3O ions than water at a pH of 7. The pH of a solution can be measured with litmus paper or with some other chemical indicator that changes color at various pH levels. Buffers The control of pH is important for living systems. Enzymes can function only within a very narrow pH range. The control of pH in organisms is often accomplished with buffers. Buffers are chemi- cal substances that neutralize small amounts of either an acid or a base added to a solution. As Figure 2-14 shows, the composition of your internal environment—in terms of acidity and alkalinity— varies greatly. Some of your body fluids, such as stomach acid and urine, are acidic. Others, such as intestinal fluid and blood, are
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