Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
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Question: Context: Elements form compounds when they combine chemically. Their atoms join together to form molecules, crystals, or other structures. The atoms are held together by chemical bonds. A chemical bond is a force of attraction between atoms or ions. It occurs when atoms share or transfer valence electrons. Valence electrons are the electrons in the outer energy level of an atom. You can learn more about chemical bonds in this video: MEDIA Click image to the left or use the URL below. URL: Look at the example of water in Figure 7.1. A water molecule consists of two atoms of hydrogen and one atom of oxygen. Each hydrogen atom has just one electron. The oxygen atom has six valence electrons. In a water molecule, two hydrogen atoms share their two electrons with the six valence electrons of one oxygen atom. By sharing electrons, each atom has electrons available to fill its sole or outer energy level. This gives it a more stable arrangement of electrons that takes less energy to maintain. Water (H2 O) is an example of a chemical compound. Water molecules always consist of two atoms of hydrogen and one atom of oxygen. Like water, all other chemical compounds consist of a fixed ratio of elements. It doesnt matter how much or how little of a compound there is. It always has the same composition. Elements are represented by chemical symbols. Examples are H for hydrogen and O for oxygen. Compounds are represented by chemical formulas. Youve already seen the chemical formula for water. Its H2 O. The subscript 2 after the H shows that there are two atoms of hydrogen in a molecule of water. The O for oxygen has no subscript. When there is just one atom of an element in a molecule, no subscript is used. Table 7.1 shows some other examples of compounds and their chemical formulas. Name of Compound Electron Dot Diagram Numbers of Atoms Chemical Formula Name of Compound Hydrogen chloride Electron Dot Diagram Numbers of Atoms H=1 Cl = 1 Chemical Formula HCl Methane C=1 H=4 CH4 Hydrogen peroxide H=2 O=2 H2 O2 Carbon dioxide C=1 O=2 CO2 Problem Solving Problem: A molecule of ammonia consists of one atom of nitrogen (N) and three atoms of hydrogen (H). What is its chemical formula? Solution: The chemical formula is NH3 . You Try It! Problem: A molecule of nitrogen dioxide consists of one atom of nitrogen (N) and two atoms of oxygen (O). What is its chemical formula? The same elements may combine in different ratios. If they do, they form different compounds. Figure 7.2 shows some examples. Both water (H2 O) and hydrogen peroxide (H2 O2 ) consist of hydrogen and oxygen. However, they have different ratios of the two elements. As a result, water and hydrogen peroxide are different compounds with different properties. If youve ever used hydrogen peroxide to disinfect a cut, then you know that it is very different from water! Both carbon dioxide (CO2 ) and carbon monoxide (CO) consist of carbon and oxygen, but in different ratios. How do their properties differ? There are different types of compounds. They differ in the nature of the bonds that hold their atoms together. The type of bonds in a compound determines many of its properties. Three types of bonds are ionic, covalent, and metallic bonds. You will read about these three types in later lessons. You can also learn more about them by watching this video: (7:18). MEDIA Click image to the left or use the URL below. URL: Chocolate: Its been revered for millennia by cultures throughout the world. But while its easy to appreciate all of its delicious forms, creating this confection is a complex culinary feat. Local chocolate makers explain the elaborate engineering and chemistry behind this tasty treat. And learn why its actually good for your health! For more information on the science of chocolate, see [Link] . MEDIA Click image to the left or use the URL below. URL: 
 Question: force of attraction between atoms or ions that share or transfer electrons

Answer: chemical bond


Question: Context: Work is defined differently in physics than in everyday language. In physics, work means the use of force to move an object. The teen who is playing tennis in Figure 16.1 is using force to move her tennis racket, so she is doing work. The teen who is studying isnt moving anything, so she is not doing work. Not all force that is used to move an object does work. For work to be done, the force must be applied in the same direction that the object moves. If a force is applied in a different direction than the object moves, no work is done. Figure 16.2 illustrates this point. The stick person applies an upward force on the box when raising it from the ground to chest height. Work is done because the force is applied in the same direction as the box is moving. However, as the stick person walks from left to right while holding the box at chest height, no more work is done by the persons arms holding the box up. Thats because the force supporting the box acts in a different direction than the box is moving. A small amount of work in the horizontal direction is performed when the person is accelerating during the first step of the walk across the room. But other than that, there is no work, because there is no net force acting on the box horizontally. Work is directly related to both the force applied to an object and the distance the object moves. It can be represented by the equation: Work = Force Distance This equation shows that the greater the force that is used to move an object or the farther the object is moved, the more work that is done. You can see a short video introduction to work as the product of force and distance at this link: . To see the effects of force and distance on work, compare the weight lifters in Figure 16.3. The two weight lifters on the left are lifting the same amount of weight, but the bottom weight lifter is lifting the weight a longer distance. Therefore, this weight lifter is doing more work. The two weight lifters on the bottom right are both lifting the weight the same distance, but the weight lifter on the left is lifting a heavier weight. Therefore, this weight lifter is doing more work. The equation for work given above can be used to calculate the amount of work that is done if force and distance are known. For example, assume that one of the weight lifters in Figure 16.2 lifts a weight of 400 newtons over his head to a height of 2.2 meters off the ground. The amount of work he does is: Work = 400 N 2.2 m = 880 N m Notice that the unit for work is the newton meter. This is the SI unit for work, also called the joule (J). One joule equals the amount of work that is done when 1 newton of force moves an object over a distance of 1 meter. Problem Solving Problem: Todd pushed a 500 N box 4 meters across the floor. How much work did he do? Solution: Use the equation Work = Force Distance. Work = 500 N 4 m = 2000 N m, or 2000 J You Try It! Problem: Lara lifted a 100 N box 1.5 meters above the floor. How much work did she do? Did you ever rake leaves, like the woman in Figure 16.4? It can take a long time to do all that work. But if you use an electric leaf blower, like the man in the figure, the job gets done much sooner. Both the leaf blower and the rake do the work of removing leaves from the yard, but the leaf blower has more power. Thats why it can do the same amount of work in less time. Power is a measure of the amount of work that can be done in a given amount of time. Power can be represented by the equation: Power = Work Time In this equation, work is measured in joules and time is measured in seconds, so power is expressed in joules per second (J/ 
 Question: Work is directly related to the force applied to an object and to the

Answer: distance the object moves.


Question: Context: The Bat has struck again, making off with a priceless necklace even after warning the police that he would rob the safe at precisely 1 a.m., after which he intends to go to country in order to give the police a rest. On his way through the village of Oakdale, the Bat notices someone robbing the Oakdale bank. Intrigued, the Bat follows the robber, who leads him to the old Fleming mansion.Inside the Fleming mansion, Cornelia van Gorder [Grayce Hamptom] and her ditzy maid Lizzie Allen [Maude Eburne] are discussing Cornelia's decision to rent the house for the summer. The big old house is a scary place, and Lizzie doesn't like the strange sounds, the strange caretaker [Spencer Charters], and the strange stories he tells about seeing ghosts in the house. Add to the fact that the Bat has taken to the country, and Lizzie is terrified of everything and anything. She's even gone so far as to set a bear trap outside her bedroom window, just in case the Bat decides to pay a vist. When Cornelia's niece Dale [Una Merkel], who works at the Oakdale Bank, returns home with her boyfriend Brook Bailey[William Bakewell] and tries to pass him off as a gardener, Cornelia is immediately suspicious (Cornelia: Any experience with alopecias? Brook: They dry up if you don't water them.), but Cornelia hires him anyway, at least until she can find out why Dale has brought him home.A rock suddenly comes crashing through the window. A note on it reads: Get out of the house now while there is still time. Immediately thereafter, Dr Venrees [Gustav von Seyffertitz] drops by to inform Cornelia that the Oakdale bank has been robbed of a half million dollars and that Fleming, Sr, the owner of the mansion, is returning from Europe so Cornelia will have to vacate the house. Then, a heavy painting moves, and a voice from behind warns them to get out of the house. Becoming concerned, Cornelia phones the police. When Detective Anderson [Chester Morris] shows up, Cornelia explains her suspicion that Fleming, Jr [Hugh Huntley] is trying to frighten her out of the house, possibly because he rented it to her while his father was out of the country. Nowthat his father is returning, she thinks he may be trying to frighten her into leaving.Soon everyone begins acting suspiciously. The doctor unlocks the broken window and "forgets" to relock it until Cornelia relocks it herself. Alone in the parlor for a few moments, Venrees unlocks the window again. Brook starts going around the house pounding on the walls. Dale phones Fleming Jr and asks him to come over. When he does, he brings a blueprint of the house so that they can locate a hidden room. Before they can find it, he is murdered, and Dale hides a piece torn from the blueprint under a tray. A storm is approaching, and the lightning knocks out the electricity. Someone phones from the garage, but when Det Anderson goes out to check, there is no one there. Detective Jones [Charles Dow Clark] arrives to help with the investigation. Dr Venrees finds the torn piece from the blueprint showing that the hidden room is behind a fireplace, but Det Anderson forces him to hand it over. When Anderson is poring over the blueprint, Venrees clobbers him with a heavy statue and locks his body in a closet. In the lightning flashes, the silhouette of the Bat can be seen peering into the window.It gets even more intriguing. Brook turns out to be a cashier from the bank and the primary suspect in the theft. Fleming Sr is seen walking on the roof when he's supposed to be out of the country. Dale finds the secret room behind a fireplace and gets locked in, along with the Bat, Mr Fleming Sr, and the money. The Bat shoots Fleming Sr. Dale escapes and leads Inspector Jones, Cornelia, and Dr Venrees to the secret room. Just as the fireplace swings open, Venrees blows out the candle, allowing whomever was in the room to escape. Finally, 
 Question: What is the name of the mysterious criminal?

Answer:
the bat.