The 10.1 Labs

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Lab: Chemical Processes Objectives • Understand the difference between endothermic and exothermic processes. • Understand the concept of enthalpy. Introduction If you’ve participated in sports, spent anytime snowboarding, camping, or fishing; chances are, you’ve seen either an instant hot pack or cold pack. Cold packs are great ways to treat minor sprains. You simply squeeze the cold pack and in just a few minutes, the selfcontained device delivers ice cold relief to the injured area. A similar product, available at many large grocery stores, was developed by a world famous chef – it’s the instant cup of hot coffee. You simply press a button on the bottom of the container, shake the contents, and wait about five minutes before drinking a steaming cup of hot, gourmet coffee. Figure 1: NASA engineers test the Russian RD-180 rocket engine in order to measure the performance of the Atlas III rocket propulsion system. The combustion of a mixture of liquid oxygen and kerosene acts as a powerful propellant producing an extreme exothermic reaction. These devices rely on chemical reactions and consequently the transfer of heat during that reaction. During a chemical reaction new products are formed as the reactants are brought together. This transformation of matter requires a transfer of heat. Energy bonds which hold the original material together must be broken, this can only happen with an application of energy. Creating a new substance also requires energy to form new bonds. During any chemical reaction energy must either be released or absorbed. © KC Distance Learning Both the cold pack and the instant cup of hot coffee combine chemicals to transfer energy. Energy can be released in a variety of forms including heat, light, or sound; however, almost every chemical reaction transfer energy as heat. During a reaction, energy is transferred between the “system” (the area where the reaction takes place) and the “surroundings” (everything outside the system). Energy can “exit” the system and move to the surroundings as in an exothermic reaction; however, energy can also move in the opposite direction. In an endothermic reaction energy “enters”, or is drawn into the system from the surroundings. Since most energy transfer occurs as heat, exothermic reactions may produce warmth while endothermic reactions may produce a cooling affect in the surroundings. Exothermic Reaction: reactants → products + energy Endothermic Reaction: reactants + energy → products The reaction of the chemicals in the cold pack, the hand warmers, and the instant hot coffee require a transfer of energy. Most common cold pack products use ammonium nitrate (NH4NO3) to create a reaction with water (H2O). While most chemical hand warmers rely on the addition of salt (NaCl) to accelerate the oxidation reaction of iron (Fe) and oxygen (O2), usually a very slow process. One interesting design component of hand warmers is the permeable plastic mesh bag which regulates the flow of oxygen to control the desired amount of heat generated during the reaction. Visit this website to see the technology behind the instant cup of hot coffee -- the flash animation on the home page of the site is also very informative. Enthalpy describes the quantity of energy contained in a chemical process. Enthalpy does not have an absolute quantity, but a change in enthalpy can be observed and recorded. On most occasions, if you stick your finger into a glass of cold tap water, it probably feels cold. Try the same simple experience after spending a time building a © KC Distance Learning snowman on a freezing winter day. The same glass of water may actually feel warm to touch. Measuring the absolute quantity of energy in the water would be difficult; however, it is relatively easy to notice the movement of energy between finger and water. Heat energy released in exothermic reactions produces a negative enthalpy. Conversely, heat energy absorbed in an endothermic reaction produces a produces a positive enthalpy. Pre-lab Questions 1. In your own words, what is the definition of enthalpy? 2. What is the relationship between the classification of a reaction as endothermic or exothermic and the enthalpy of the reaction? 3. Chemicals combine in instant cold packs and the temperature of the mixture decreases. Is this an exothermic or endothermic process? © KC Distance Learning Experiment: Hand Warmers vs. Cold Packs During this lab activity you will observe temperature changes produced by the activation of chemicals in instant cold and hot packs. Temperature is the measurement of the average kinetic energy of the molecules within a substance and can therefore be used to indicate a change in energy. You will create a simple calorimeter using a Styrofoam cup and thermometer to capture and measure the energy of the reaction. Follow all safety precautions and use the proper safety equipment during this experiment. Be sure to make careful observations during each phase of the experiment. Materials • Safety Equipment: Eye goggles, gloves • Plastic stir stick or chop stick • Contents of hand-warmer packet • Spatula made from plastic straw • ¼ contents of cold packet • Measuring cup • Calorimeter (1 12oz. Styrofoam cup) • Measuring spoons • Stop watch (tracking time in seconds) • Distilled water • Thermometer © KC Distance Learning Procedure 1. Prepare a clean area in your kitchen to safely conduct the experiment. 2. Collect all of the materials from the materials list – do not combine materials until you have completely read through the lab instructions. 3. Be sure to wear both your safety goggles and gloves when handling any chemicals. Part 1: Cold Pack 4. Measure 2 teaspoons (10 mL) of distilled water into a measuring cup. 5. Place about 1/4 (or approximately 10.0 g) of the ammonium nitrate crystals found in the solid inner contents of a cold pack into a Styrofoam cup. The Styrofoam cup is used as a simple calorimeter. 6. Place a thermometer and a stirring rod into the calorimeter (Styrofoam cup). CAUTION: Hold or secure the calorimeter AND the thermometer to prevent breakage. 7. Pour the 10 mL of water into the calorimeter containing the ammonium nitrate, (NH4NO3). 8. Immediately record the temperature and the time. 9. Quickly begin stirring the contents in the calorimeter. 10. Continue stirring and record the temperature at thirty second intervals in Table 1. You will need to stir the reaction the entire time you are recording data. 11. Collect data for at least five minutes and until after the temperature reaches its minimum and then begins to rise. This should take approximately 5 to 7 minutes. 12. Record the overall minimum temperature in the appropriate place on the data table. Part 2: Hand Warmer 1. Wash and dry the thermometer. HINT: Remember to rinse it with distilled water before drying. 2. Carefully place and hold the thermometer in another Styrofoam cup. © KC Distance Learning 3. Cut open the inner package of a hand warmer and quickly transfer all of its contents into the calorimeter. Immediately record the initial temperature of the contents and being timing the reaction. HINT: Data collection should start quickly after the package is opened because the reaction will be activated as soon as it is exposed to air. 4. Quickly insert the stirring rod into the cup and begin stirring the contents in the calorimeter. 5. Continue stirring and record the temperature at thirty second intervals in Table 2. You will need to stir the reaction the entire time you are recording data. 6. Let the reaction continue for at least five minutes and until the temperature has reached its maximum and then fallen a few degrees. This should take approximately 5 to 7 minutes. 7. Record the overall maximum temperature in the appropriate place in the data table. 8. Dispose of the components of both solutions through approved household methods. 9. Dispose of the solid components through approved household methods. 10. Clean your equipment and work area using approved cleaning procedures. © KC Distance Learning Data and Observations Table 1 Time (sec) Initial Cold Pack Data Temp. (°C) Time (sec) 240 30 270 60 * 300 90 330 120 360 150 390 180 420 210 450 Temp. (°C) Minimum Temperature (°C): _______________ © KC Distance Learning Table 2 Time (sec) Initial Hand Warmer Data Temp. (°C) Time (sec) 240 30 270 60 * 300 90 330 120 360 150 390 180 420 210 450 Temp. (°C) Maximum Temperature (°C): _______________ © KC Distance Learning Graph Graph the data from Tables 1 and 2 as two separate lines on the same chart. Be sure to title your graph and label each axis. Include the units in the axis labels. An example is shown here. Use the following space to graph your data: © KC Distance Learning Post-lab Questions 1. Which pack works by an exothermic process? Use experimental data to support your answer. 2. Which pack works by an endothermic process? Use experimental data to support your answer. 3. Which pack had the greatest change in enthalpy? How do you know? © KC Distance Learning Lab: Heat and Calorimetry Objectives • Gain applicable knowledge about calories • Compare the calorie content of food samples Introduction Most people are aware that foods contain calories, but what is a calorie? A calorie is the amount of energy necessary to raise the temperature of 1 gram of water 1 degree Celsius. Your body burns the energy contained in the foods you eat. On average, most people burn approximately 2000 calories per day. Have you noticed that your body feels warmer the more you exercise? That is because heat is one way that energy is transferred. Figure 1: Federally required nutrition labels provide people with information about the amount of energy contained in each serving. The labels also provide other nutritional information. One of the physical properties of any substance is specific heat. Specific heat is the energy required to raise the temperature of 1.00 gram of the substance by 1 degree Celsius. In Table 1, you can view the specific heat of many common substances. In this laboratory experiment, you will burn food to measure the amount of heat energy it produces – from that you will be able to determine the amount of calories (energy) that food contains. The equation below shows the relationship between the amount of energy, in the form of heat, which is added to a substance to change the temperature of that substance: E = mc∆T E = Energy measure in calories m = mass of the substance in grams c = specific heat in cal/g-°C ∆T = the change in temperature (°C or K) © KC Distance Learning In order to measure the temperature of a food sample, you will need to burn it and measure the amount of heat it gives off. You will need to construct a calorimeter to measure the heat produced from the burning material – this is referred to as an indirect measurement. The heat from the burning food sample will heat a container filled with water. A thermometer will measure the change in temperature of the water. Since energy is always conserved, the heat absorbed by the water from the burning food sample will provide us with the information necessary to calculate the amount of energy contained in the food sample. The amount of energy in food is measured in Calories. One Calorie (with a capital “C”) is equivalent to 1 kilocalorie, or 1000 calories (with a lowercase “c”). Substance Cal/g·K Gold 0.0301 Lead 0.0305 Copper 0.0923 Iron 0.110 Glass 0.200 Aluminum 0.215 Wood 0.400 Alcohol 0.580 Water 1.000 Table 1: Specific heat of common substances. Example Calculation: Here’s an example on the steps necessary to calculate the calories in a piece of food. This is accomplished by measuring the amount of energy transferred by heating 100.0 milliliters of water from 24 to 36.5 degrees Celsius by burning a marshmallow which masses at 1.500 grams. 1. Determine the mass of the water heated: Mass = Density x Volume m = (1.00 g/mL) x (100.0 mL) = 100 g 2. Apply the constant for the specific heat of water: c = 1.00 cal/g°C 3. Calculate the change in the temperature of the water: ∆T = (36.5°C - 24°C) = 12.5°C © KC Distance Learning 4. Calculate the energy lost by the marshmallow – this equals the energy gained by the water: E = mc∆T E = (100.0 g) x (1.00 cal/g°C) x (12.5°C) = 1250 cal 5. Calculate the calories per gram of marshmallow: calories/g marshmallow = 1250 cal 1.500 g = 833.3 cal/g 6. Convert from calories to Calories (kilocalories) per gram of marshmallow: calories/g marshmallow = 833.3 cal g x 1 Cal = 0.833 Calories/g 1000 cal Pre-lab Questions 1. How does a food calorie differ from a food Calorie? What does a calorie measure in terms of food? 2. A gummie bear was tested through a flame-calorimeter test. The bear had a mass of 1.850 grams and the temperature of 100.0 milliliters of water increased by 15.0 degrees Celsius. How many Calories were in the gummie bear? Show all of your calculations. © KC Distance Learning Experiment: Heat and Calorimetry CAUTION: In this experiment, you will be working with fire, hot water, and heated metal. The experiment will produce smoke. Be sure to work in a well ventilated area, such as a stove hood, or near an open window and with the supervision of an adult. DO NOT burn foods that you know you are allergic to – such as peanuts. You will need to construct a calorimeter with the equipment listed. Be sure that the thermometer does not touch the sides or bottom of the soda can. Materials • • • • • • • • • • • • Eye googles or safety glasses and gloves Large (unfolded) paper clips Butane lighter Thermometer Cork from bottle (2) 12 ounce aluminum soda can Tripod (can be constructed from tin can or wire coat hanger and canning lid) Snack foods from container with nutrition label Water Glass jars Measuring cups Kitchen measuring scale © KC Distance Learning Procedure 1. Measure 1 cup (118 milliliters) of distilled water. 2. Carefully pour the measured water into an empty aluminum soda can. 3. Set the aluminum can on the tripod as shown in Figure 1. 4. Insert a thermometer into a split cork to use as a stopper. Place the thermometer into the can as shown in Figure 1, with the stopper resting on the top of the can. You can adjust the height of the thermometer by sliding the stopper up or down. The thermometer should touch the water but not the bottom or sides of the can. 5. Insert the end of the unfolded paper clip that is still folded into a cork. 6. Tear a junk food sample into a piece that is about 1 centimeter squared (cm2). Determine the mass of the piece of junk food and record it in the data table. NO eating in the lab! © KC Distance Learning 7. Insert the straightened end of the food holder into the sample. HINT: If this does not hold the sample you can make a loop at the end of the paper clip to rest the sample in. 8. Fill a large glass jar or bowl approximately half full of water near your calorimeter. Use this to extinguish smoke after the sample has finished burning. 9. In Table 1, record the initial temperature of the water inside the aluminum can. 10. Light the butane lighter. CAUTION: Burns can occur with the use of flames. 11. Hold the cork end of the sample holder and carefully bring the sample into the flame until it ignites. HINT: The sample should be held in the flame for a few seconds to assure the sample will burn strongly. 12. Immediately and carefully bring the burning food approximately 1 centimeter below the bottom of the aluminum can in order to minimize the amount of heat lost. CAUTION: Excessive smoke can result from the ignited sample and can be a respiratory irritant. If there is excessive smoke, relight the sample immediately. 13. Watch the thermometer as the food sample completely burns to ash. If the food sample goes out before it is completely burned or is producing only a little flame and excessive smoke, quickly relight it in the lighter flame and place it back under the aluminum can. Record the maximum temperature that is reached. 14. Immediately after the sample has completely burned, dip it into the beaker of water and wait for it to cool. 15. Place the remains of the sample in the trash. Wash end of the paper clip, and then dry it with a paper towel. 16. Repeat steps 7-16 using other foods from your pantry. (Hint: Use a sample size that has a similar mass to the previous sample.) © KC Distance Learning Data Junk Food Sample A (Specify) Sample B (Specify) Sample C (Specify) Sample D (Specify) Volume of Water (mL) Mass of Water (g) Mass of Food Sample (g) Initial Water Temp. (°C) Max. Water Temp. (°C) Water ∆T (°C) 118 mL 118 mL 118 mL 118 mL Calculations 1. If all of the heat from the food sample was transferred to the water in the can, calculate the Calories per gram that each sample contains. Remember, Calories are measured in kilocalories. a. Food sample A b. Food sample B © KC Distance Learning c. Food sample C d. Food sample D 2. Use the information from the nutrition facts label, including the serving size, to calculate the amount of calories each food contains. a. Food sample A b. Food sample B © KC Distance Learning c. Food sample C d. Food sample D © KC Distance Learning Post-lab Questions 1. Which food sample had the highest number of calories per gram? Were you surprised by these findings? 2. Did your measurements match those reported by the food manufacturer? 3. Where did error most likely occur in this experiment? 4. Is it important for the food to completely burn? Why or why not? 5. How could the experiment be modified to reduce the amount of error? © KC Distance Learning
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Hello,I have completed your work but for number 1 of the second experiment it was not doable without your experimental results. As for the calculations of the second assignment also I had to assume based on research the values of the changes in temperature for your samples.Thank you.Goodbye, it was a pleasure working with you.

Chemical processes assignment
Pre-Lab Questions
1.Enthalpy is a measure of energy given off or consumed in a reaction.
2. An exothermic r...

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