Coffee-cup

The annual production of styrene in the United States is approximately 1 2 X 10 lb with about 65% of this output used to prepare polystyrene plastics and films Styrofoam coffee cups are made from polystyrene Polystyrene can also be produced m a form that IS very strong and impact resistant and is used widely m luggage television and radio cabinets and furniture... 

Polymers are a fundamental part of the modem world, showing up in everything from coffee cups to cars to clothing. In medicine, too, their importance is growing for purposes as diverse as cardiac pacemakers, artificial heart valves, and biodegradable sutures. 

Coffee-cup calorimeter. The heat given off by a reaction is absorbed by the water. If you know the mass of the water, its specific heat (4.18 J/g °C), and the temperature change as read on the thermometer, you can calculate the heat flow, q. for the reaction. 

A simple experiment with a coffee-cup calorimeter shows that when one gram of NH4N03 dissolves, fraction = 351 J. The calorimeter is open to the atmosphere, the pressure is constant, and... 

As noted earlier, for a reaction at constant pressure, such as that taking place in an open coffee-cup calorimeter, the heat flow is equal to the change in enthalpy. If a reaction is carried out at constant volume (as is the case in a sealed bomb calorimeter) and there is no mechanical or electrical work involved, no work is done. Under these conditions, with w = 0, the heat flow is equal to the change in energy, AE. Hence we have... 

Coffee-cup calorimeter Bomb calorimeter Standard enthalpy change First law of thermodynamics AH versus AE... 

Magnesium sulfide is often used in first-aid hot packs, giving off heat when dissolved in water When 2.00 gof MgS04 dissolves in 15.0 mL of water (d = 1.00 g/mL) at 25°C in a coffee-cup calorimeter, 151 kj of heat is evolved... 

Human engineering. While the designer usually regards the problems of space limitations as being appearance related, they are most often the outcome of the ID s concern for human engineering, or the proper relationship of the product to the human body. For example, personal computers should be small enough to be carried by many people, coffee-cup handles should be comfortable to the hand, eyeglass frames should be easy on the ears, etc. 

C06-0017.A coffee-cup calorimeter is calibrated using a small electrical heater. The addition of 3.45 kJ of electrical energy raises the calorimeter temperature from 21.65 °C to 28.25 °C. Calculate the heat capacity of the calorimeter. 

CO6-OO66. When 5.34 g of a salt dissolves in 155 mL of water (density = l.OOg /niL) in a coffee-cup calorimeter, the temperature rises from 21.6 °C to 23.8 °C. Determine q for the solution process, assuming that Ccal = Crater ... 

C06-0067. When 10.00 mL of a solution of a strong acid is mixed with 100.0 mL of a solution of a weak base in a coffee-cup calorimeter, the temperature falls from 24.6 °C to 22.7 °C. Determine q for the acid -base reaction, assuming that the liquids have densities of 1.00 g/mL and the same heat capacity as pure water. 

C06-0111. A coin dealer, offered a rare silver coin, suspected that it might be a counterfeit nickel copy. The dealer heated the coin, which weighed 15.5 g, to 100.0 °C in boiling water and then dropped the hot coin into 21.5 g of water at =15.5°C ina coffee-cup calorimeter. The temperature of the water rose to 21.5 °C. Was the coin made of silver or nickel ... 

Total caffeine consumption will vary with a number of factors that are often difficult to disentangle. For caffeine exposure attributable to coffee, this includes brewing method and preparation type of coffee (Arabica, Robusta, instant), averaging to 1.3% caffeine for roasted beans 39 brand of coffee size of coffee cup and the volume of added ingredients, such as milk, cream sweeteners, and syrups. There are several different brewing or preparation techniques by which coffee can be prepared. Most notably, they differ in their final extraction of caffeine depending on the process. Filter coffee or automatic drip coffee results in approximately 97 to 100% caffeine extraction 37 however, regional differences in the volume of coffee... 

She watched me intently. "Farben again," she said. Her coffee cup clattered nervously in the saucer. 

The three-dimensional APH display may be conveniently chosen to map onto a simple cylindrical surface (e.g., a coffee cup) by adding blank filling space to each helical turn in order to maintain a constant radius of curvature. Figure B.3 provides a simple planar template that one can cut and paste to form the APH cylindrical display. 

We say a pure liquid boils when its vapour pressure equals the external, atmospheric pressure (see p. 188). Similarly, when boiling a mixture, boiling occurs when the sum of the partial pressures (P(water) + P(coffee)) equals p . It is for this reason that the steam above the coffee cup smells strongly of coffee, because the vapour contains the essential oils (e.g. esters) that impart the smell. But the water generates steam at a pressure of p% when the water added to the cup is boiling, so the partial pressure of the coffee P(COffee) is additional. For this reason, we produce more steam than above the cup containing only water. 

Scenario A student constructed a coffee cup calorimeter (see Figure 1). To determine the heat capacity of the calorimeter, the student placed 50.0 mL of room temperature distilled water in the calorimeter. A calibrated temperature probe recorded the temperature as 23.0°C. The student then added 50.0 mL of warm distilled water (61.0°C) to the calorimeter and recorded the temperature every 30 seconds for the next three minutes. The calorimeter was then emptied and dried. Next, the student measured the temperature change when 50.0 mL of... 

Some of these interacting objects may be computer systems. We can treat them as single objects and describe their interactions with the world around them. Subsequently, we refine the system into a community of interacting software objects (see Figure 6.12). (A standard OO design is based on a model of the external world so that we now have two of everything a real coffee cup, a user, and a coin, plus their representations inside the software.) When we look inside the software, we can continue to use the more general multi-... 

For a patient suffering from diarrhea, a doctor advised the patient to take one glassful of an electrolyte solution three times a day. The patient took one coffee-cupful of medication three times for one day. How much extra medication was the patient supposed to take ... 

Calorimetry involves the use of a laboratory instrument called a calorimeter. Two types of calorimeters are commonly used, a simple coffee-cup calorimeter and a more sophisticated bomb calorimeter. In both, we carry out a reaction with known amounts of reactants and the change in temperature is measured. Check your textbook for pictures of one or both of these. 

The coffee-cup calorimeter can be used to measure the heat changes in reactions that are open to the atmosphere, qp, constant pressure reactions. We use this type of calorimeter to measure the specific heats of solids. We heat a known mass of a substance to a certain temperature and then add it to the calorimeter containing a known mass of water at a known temperature. The final temperature is then measured. We know that the heat lost by the added substance (the system) is equal to the heat gained by the surroundings (the water and calorimeter, although for simple coffee-cup calorimetry the heat gained by the calorimeter is small and often ignored) ... 

Many of the reactions that chemists study are reactions that occur at constant pressure. During the discussion of the coffee-cup calorimeter, the heat change at constant temperature was defined as qp. Because this constant-pressure situation is so common in chemistry, a special thermodynamic term is used to describe this energy enthalpy. The enthalpy change, AH, is equal to the heat gained or lost by the system under constant-pressure conditions. The following sign conventions apply ... 

To determine enthalpy changes in high school laboratories, a coffee-cup calorimeter provides fairly accurate results. A coffee-cup calorimeter is composed of two nested polystyrene cups ( coffee cups ). They can be placed in a 250 mL beaker for added stability. Since a coffee-cup calorimeter is open to the atmosphere, it is also called a constant-pressure calorimeter. 

As with any calorimeter, each part of the coffee-cup calori-meter has an associated heat capacity. Because these heat capacities are very small, however, and because a coffee-cup calorimeter is not as accurate as other calorimeters, the heat capacity of a coffee-cup calorimeter is usually assumed to be negligible. It is assumed to have a value of 0 J/ C. 

A coffee-cup calorimeter is well-suited to determining the enthalpy changes of reactions in dilute aqueous solutions. The water in the calorimeter absorbs (or provides) the energy that is released (or absorbed) by a chemical reaction. When carrying out an experiment in a dilute solution, the solution itself absorbs or releases the energy. You can calculate the amount of energy that is absorbed or released by the solution using the equation mentioned earlier. 

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