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### 46 Cards in this Set

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 Why are flames considered a form of energy? Whenever matter undergoes a substantial change, that change is accompanied by either a release or an intake of energy. Why would it not be considered work for a person to be pushing against a wall with all of his might? In order for work to occur, there must be motion. When you push against a wall with all of your might, you are doing no work . Only if the wall actually moved would you, in fact, be doing work. Why is heat considered a special form of energy? Heat is a special form of energy: energy that is on its way from a hot body to a cold body. Heat always travels from hot to cold. If there is no difference in temperature, there is no heat. Does a pile of wood have energy in it? Yes. The energy is trapped, or stored, inside the wood and cannot be transferred to you until the wood is burned. When the wood burns, the energy that has been stored there is released and transferred to you in the form of heat. What is the problem with Scientific Law? The problem with putting too much faith in a scientific law is that the experiments which established it might be flawed, making the scientific law itself flawed. How does the First Law of Thermodynamics apply to the act of a person starting a wood fire? When you start a fire, you are changing the form of the energy that is already in the wood and the surrounding air. So in a fire, energy is not created; it is simply changed from potential to kinetic energy. True or False? All substances have energy stored in them. True. All substances have energy stored in them; thus, all substances have potential energy. True or False? You can measure energy in its potential form. True. When in potential form, energy is very difficult to measure. There are ways of doing it however! In order to measure heat, you must first measure _______? temperature Temperature and heat are the same thing. False... Temperature and heat are not the same, but they are related to each other. How does a thermometer work? A thermometer makes use of the fact that substances tend to expand as they get warmer. Thus, a thermometer consists of a substance (usually mercury or alcohol) that is contained in a column of glass. As the substance gets warmer, it begins to expand. Since the only way it can expand is in the upward direction, it begins to move up the glass column. The height that it moves up the column is directly related to the temperature Rather than use Fahrenheit as a temperature unit, what unit/units do chemists use instead? Celsius (abbreviated °C) or Kelvin (abbreviated K). If ice and water are thoroughly mixed, the temperature of the mixture will stay the same regardless of the amount of ice or water present. What is that temperature in Fahrenheit and in Celsius? 0.0 °C or 32.0 °F Boiling water is always at the same temperature whether it is boiling rapidly or hardly boiling at all. What temp would that be? 100 °C or 212 °F at standard atmospheric pressure What is the equation used for converting Fahrenheit into Celsius? °C = 5/9 (°F- 32) (5/9 is five ninths) Normal body temperature is 98.6 oF. What is this temperature in Celsius? 37.0 °C If water boils at 100.0 °C, what is the boiling temperature of water in Fahrenheit? 212.0 °F True or False? In both the Fahrenheit and Celsius measurements, you can go below zero degrees. True. Temperatures less than zero are quite common in the Celsius scale. Although not quite as common, it is also possible to reach temperatures less than zero in the Fahrenheit scale as well. Once you have your temperature in units of degrees Celsius, converting it to Kelvin is possible with the following equation: ________________ K = °C + 273.15 What is the Fahrenheit equivalent of 0.00 Kelvin? -459.67 °F (if you have problems with this conversion, the step by step explanation is in your book under "On Your Own" problems..... ) Since Joules and calories really measure the same thing, how many Joules are in one calorie? 1 calorie = 4.184 Joules Most of the things that you do (walking, running, breathing, even sitting down and reading a book) involve work. Since work requires energy, your body needs a steady supply of it. Where does that energy come from? Your body gets the energy it needs from the food you eat. The food Calorie and the chemistry calorie are the same thing. True or False? False. The food Calorie (notice the capital “C” here) is not the same as a chemistry calorie (written with a small “c”). Food generally contains an enormous amount of energy; therefore, the calorie as we defined it earlier is simply too small a unit to use when measuring the energy content of food. How many chemistry calories are in one food calorie? 1 food calorie (Cal) = 1,000 chemistry calories (cal) The temperature change in an object is related to the amount of heat it absorbs or releases by the following equation: q = m·c·ΔT In this equation, “q” stands for the amount of heat absorbed or released, “m” represents the mass of the object, and “c” is the specific heat of the object ΔT is discussed in another flashcard.... “ΔT” (pronounced “Delta T”), stands for the change in temperature and is defined as the difference between the final temperature and the initial temperature. What is the equation for this? ΔT = T final - T initial Does wood or metal have a lower specific heat? Metals have a lower specific heat. Since metals have low specific heats, a small amount of heat changes the temperature significantly. Which substance takes the least energy to heat up, copper or glass? (refer to Table 2.1 unless you memorized it!) Copper has a lower specific heat than glass. This means that copper is easier to heat up. A copper kettle and an iron kettle are placed side by side on a fire. After 5.0 minutes on the fire, the iron kettle reaches a temperature of 100.0 °C. Will the copper kettle's temperature be higher or lower than 100.0 °C? (refer to Table 2.1 unless you memorized it) Since both kettles are on the same fire for the same amount of time, they are each getting the same amount of heat. Therefore, the kettle made out of the substance which is more difficult to heat up will be the coolest one. Since iron has a larger specific heat, it is more difficult to heat up, so it will be cooler than the copper kettle. That means the copper kettle's temperature will be higher than 100.0 °C. The unit for specific heat will have _________ in the numerator? an energy unit (calories or Joules) The unit for specific heat will have _________ in the denominator. a mass unit (grams, kg, mg, etc.) The unit for specific heat will also have _________ in the denominator. a temperature unit (°C,°F, or K) A 502 g iron rod is heated to an unknown initial temperature. If, while cooling down to a temperature of 22 °C, the rod releases 597.5 Joules of energy, what was its initial temperature? (HINT: When an object loses energy, its “q” is negative. ) 25 °C. (step by step solution found in "On Your Own") What is the specific heat of water? 1.000 cal/g.°C or 4.184 J/g.°C In the calorimetry equation, why does the -q object have a negative sign in front of it? The object is releasing heat. That means it is losing energy. If it is losing energy, its “q” will be negative. If you want to measure the amount of heat released by a substance, how would you go about doing so? If you want to measure the amount of heat released by a substance, you can surround that substance with water and a calorimeter, and measure the change in temperature of the water and the calorimeter. If you are told to ignore the calorimeter in a problem, what does that mean? If the heat absorbed by the calorimeter is so small that it did not even “show up” when we added it to the heat absorbed by the water, then you can ignore the calorimeter. This happens often in calorimetry experiments. As a result, we can often disregard the heat absorbed by the calorimeter when doing calorimeter experiments. If that is the case, then, we can treat qcalorimeter as being equal to zero. . A man pushes a stalled car for 2 minutes. During the first 1.5 minutes, the car does not move, but for the last 0.5 minutes the man pushes even harder and succeeds in getting the car to move. Is the man doing work for the entire 2 minutes? If not, does he ever succeed in doing work? If so, when? For the first 1.5 minutes, the man did no work. Motion is required in order to do work. Since the car did not move during that time, no work was done. For the last 0.5 minutes, however, the man did do work. Classify each of the following as having either potential or kinetic energy, or both: a. A lump of coal b. A flash of lightning c. A candle flame d. A tornado a. A lump of coal has potential energy in it because all matter has stored energy. b. A flash of lightning is light, so it has no matter. Thus, it cannot have potential energy. However, the lightning flash is in motion, so it has kinetic energy. c. A candle flame also has no matter, but it does have heat, so it has kinetic energy. d. A tornado is a swirling mass of air. Since air is matter, it has potential energy, but because the air is moving, it also has kinetic energy. Therefore, it has both. A chemist watches the temperature of a vat of liquid and notices that it decreases over time. What can the chemist conclude from this observation? If a substance.s temperature decreases, we can conclude that it is losing energy. If a hot object is totally insulated from the outside world (totally unable to interact with anything else), will its temperature ever be able to change? Since the object cannot interact with anything else, it will never be able to give away any of its energy or absorb energy from anything. Thus, its temperature can never change. Why should you never look to science as an ultimate source of truth? . Science is fallible. Laws which scientists thought were true for hundreds of years have later been demonstrated to be false. Since science is fallible, it is a poor source for ultimate truth. . Heat is added to two identical objects that are initially at the same temperature. If the first absorbs 100.0 cal and the second absorbs 100.0 J, which gets hotter? . Since it takes 4.184 Joules to make 1 calorie, the Joule is a smaller energy unit. Thus, the object which absorbs 100.0 cal is absorbing more energy and will therefore be the hottest. Some diet books tell you that an excellent way to lose weight is to drink ice-cold water. Why? . Your body has an internal temperature of about 37 oC. Ice water has a temperature of 0.0 oC. Your body must therefore warm up the water. That takes energy, which your body gets from the food that you eat. Thus, drinking ice-cold water is a way of burning off excess Calories. The specific heat of iron is roughly three times that of gold. Equal masses of gold and iron start out at room temperature. Heat is added to each mass at the same rate for the same amount of time. When it is all over, the gold.s temperature increased by 900 oC. What was the temperature increase of the iron? . Since the iron has a larger specific heat, it is harder to heat up. Thus, the gold will come out hottest. Since gold.s specific heat is three times smaller than iron, we can actually conclude that it will come out three times hotter. Thus, if the gold increased in temperature by 900 oC, the iron would only increase in temperature by 300 oC. Why should a calorimeter always be made from an insulating material? A calorimeter should be made out of insulating material because energy should never be allowed to escape from it. If energy does escape from a calorimeter, the measurement you are using the calorimeter for will be in error.