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Mr Cris Son

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Figure skater Rachael Flatt, this February Hopes she will be showing off her moves that are cool in the 2010 Winter Olympic Gamesin Vancouver, Canada. "I will work quite tough to achieve this goal," says Rachael, among the highest-ranked skaters in the world.When she takes to the ice, her skates' blades glide easily over the slick surface.

And whether the athlete is landing a reverse orpreparing for a spin, ice leaves her tricks potential. But how? Keep reading to find out.Chill FactorJust like the ice cubes that trendy your Lemonade, the slab of ice under the skates of Rachael is made up of water molecules. Bothhydrogen atoms and single oxygen molecule that compose a water molecule discuss electrons.

 "However, the sharing isn't equal,"states Paul Doherty, a physicist in the Exploratorium in California. One facet of this water molecule ends up with a favorable onewith a negative charge and the other hand. This causes water molecules to be attracted to one another. When temperatures are above 0[degrees]C (32[degrees]F), water molecules jiggle and pull these links apart. The outcome? Liquidwater.

However, as temperatures dip slows down. The water molecules package and can contribute to their attraction. Liquid water turnsinto ice. That is why the ice hockey Rachael glides over is kept In a teeth-chattering -3[degrees]C (27[degrees]F). That way, spins withoutlanding in a pool of water and Rachael can show off her jumps. Slip-N-SlideGreat thing for Rachael that ice Isn't only Strong slippery too. Skaters would be met with an ear-splitting screech when theytried their stunts like concrete or glass. Why is ice slippery?

Scientists are still puzzling over this question. But physicists know 1 thing: The response given in manycollege textbooks is incorrect. Scientists used to think that a skater's Weight put pressure causing it to melt at a lower temperature. But experimentsdemonstrated that this pressure change is too little to make ice melt. Today, many scientists think a force Retains the clue: friction. When Rachael pumps her legs, her skates' blades rub against theice. This rubbing creates friction, which releases heat.

With each leg stroke, the heat warms the ice beneath the skater's feetup. When the ice's temperature climbs above freezing, a thin layer on the outside melts into liquid water (see Why Ice IsSlippery, page 14). The water acts under Rachael's skates to allow for graceful glides quick spins, and smooth landings. Liquid LayerRachael can not be too cautious on the ice rink. Whether she is landing a triple axel or making her present, there is anopportunity of slipping. May slide. This led scientists to think that there has to be more to the slipperiness than friction ofice alone. Researchers have found that ice's surface Is obviously slick. The water molecules are lined up like cars in a parking garage, withneatly ordered vehicles. But like the cars on the upper floor of the parking garage, the molecules at the upper layer of ice don'thave some molecules above them.

"[Molecules in the upper layer] are a little Fleer to maneuver about," Doherty says. These molecules behave more like a liquidthan a solid. "The surface is similar to water and allows the blades to slip," he says. That's a good thing for Rachael, that hopes to Glide across the slick ice to win a medal from the Olympic Games. Words to KnowMolecule--A group of two or more atoms that By sharing electrons are joined together.

Electron negative charge. Stress Gas. Friction when two surfaces rub against each other. ICE IS SLIPPERYMELTING BY FRICTION: A blade that is fast-moving creates friction on the ice.

This force causes heat, which melts the ice crystalsinto a thin coating of water below the skate. But this reasoning isn't the entire story. It does not explain why even a personstanding on ice can slide. BUILT-IN SLIPPERY LAYER:There is present A movie on the surface of ice. Chains of water molecules along the layer are exposed to atmosphere and are notable to form ice crystals.

It's simple to slide these chains, which vibrate such as liquid fluids. Quick quiz1. When the temperature climbs above 0[degrees]C (32[degrees]F), ice varies from a to a.(A) gas, solid(B) liquid, solid(C) liquid, gas(D) solid, liquid2. A water molecule is made from.(A) two hydrogen atoms and an oxygen molecule(B) two oxygen atoms and a hydrogen atom(C) electrons(D) ice cubes3. Which explanation for the slipperiness of ice is Widely mentioned but untrue? (A) Friction from the skate's blades melts ice.

(B) The skater puts pressure on the ice, Causing it to melt down. (C) Ice is naturally slippery due to the Top layer's construction. (D) None of the aboveANSWERS1. d 2. a 3. bBEFORE READINGSet a GoalLearn why ice is slippery and just how the Features of this solid that is common make sports such as ice. BackgroundIf you Believe all ice is the same, think again. Water ice may happen as around 15 known crystalline phases of water. Everydaysnow and ice fall known as hexagonal ice, the selection. Other types can happen under extreme temperature and pressurecombinations, either here on Earth or on other planets. * Hexagonal ice gets its name because of the Truth That the water molecules line up in a pattern.

Why all snowflakes have sixsides, that's. Discussion Question* Have you ever slipped on ice? Can you decrease Your odds of slipping by wearing certain types of sneakers? Can you think thatworks? (Answers will vary, but should include that boots with ridges for grip would reduce one's chance of slipping on ice becausethe ridges increase friction, maintaining the shoe from slipping away from under you.) AFTER READINGDiscussion QuestionTo get a tong time, scientists believed in the Incorrect explanation to the question, "Why is ice slippery?"

What are someexamples of scientists finding new concepts to replace incorrect beliefs? (Possible answers: Researchers used to believe the sunrevolved round the Earth before the discovery that it's the other way around; scientists used to believe that heavier objects fellfaster than light ones until it was demonstrated that gravity accelerates all things at the exact same pace.)

RESOURCE* Ice and Individuals, by Nikki Bundey (Carolrhoda Books, 2000). This book reviews what ice is and how animals and people dealwith cold and ice. Directions: Match the word(s) from the left Column with the term in the ideal column. 1. Pressure a. The particle within an atom that's a negative charge. 2. Molecule b. A force which acts against movement when two surfaceRub each other.3.

Electron c. A set of two or more atoms which are joinedtogether by sharing electrons At a chemical bond. 4. Friction d. A force that is applied against a gas, Fluid, orsolid.

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