Thermochemistry Notes - Adamson University

ADAMSON UNIVERSITY BED - SENIOR HIGH SCHOOL GENERAL CHEMISTRY II THERMOCHEMISTRY BIG IDEA THEME FOCUS MS. CLAIRE A. GARCIA, LPT LEARNING OBJECTIVES  ACTIVITY #2 PHYSICAL or CHEMICAL CHANGES? Directions: Determine whether the im...

ADAMSON UNIVERSITY BED - SENIOR HIGH SCHOOL GENERAL CHEMISTRY II THERMOCHEMISTRY BIG IDEA THEME FOCUS MS. CLAIRE A. GARCIA, LPT LEARNING OBJECTIVES  ACTIVITY #2 PHYSICAL or CHEMICAL CHANGES? Directions: Determine whether the image presented represents a chemical or physical change. PHYSICAL CHANGE Melting of Ice Cream Directions: Determine whether the image presented represents a chemical or physical change. CHEMICAL CHANGE Deterioration of metals Directions: Determine whether the image presented represents a chemical or physical change. PHYSICAL CHANGE Moist formation on glass Directions: Determine whether the image presented represents a chemical or physical change. CHEMICAL CHANGE Formation of precipitate (a solid formed by a change in a solution) Directions: Determine whether the image presented represents a chemical or physical change. PHYSICAL CHANGE Sublimation of solid iodine THERMOCHEMISTRY is the study of heat change in chemical reactions. it focuses on the energy changes, particularly the system's energy exchange with its surroundings. it is useful in predicting reactant and product quantities throughout a given reaction. COMMON APPLICATIONS OF THERMOCHEMISTRY COMMON APPLICATIONS OF THERMOCHEMISTRY THERMOCOLOR CUP The Thermocolor Cup is made with a special temperature-sensitive ink called thermochromic leucodye. Leucodyes are chemicals that change color when there is a temperature change of about 5°C (9°F) or more. Thermochromic leucodyes can be made to change colors at specific temperatures. The ink used to make your cup changes color at around 7-12ºC (45-50ºF). COMMON APPLICATIONS OF THERMOCHEMISTRY VACUUM FLASK Also called as thermos flask or Dewer flask (named after James Dewer in 1892). It was devised to preserve liquefied gases by preventing the transfer of heat from the surroundings to the liquid. The evacuated space between the walls (which are ordinarily glass or steel) is practically a nonconductor of heat; radiation is reduced to a minimum by silvering the glass or steel. COMMON APPLICATIONS OF THERMOCHEMISTRY FUELS AND COMBUSTION Understanding the amount of energy produced during fuel burning is made easier by thermochemistry. This is essential for creating power plants, heating systems, and engines that are more efficient. Automobile engines generate energy through an exothermic process when gasoline is burned. COMMON APPLICATIONS OF THERMOCHEMISTRY REFRIGERATION AND AIR CONDITIONING To chill the air or remove heat from places, air conditioners, and refrigerators employ endothermic processes, in which heat is absorbed. Thermochemistry aids in the energy efficiency optimization of these systems. Refrigerants in air conditioners take in heat from the space, cool it, and then expel it outside. COMMON APPLICATIONS OF THERMOCHEMISTRY COOKING Heat is essential to the chemical processes that occur during cooking. The energy needed to prepare food (baking, frying, etc.) alters the content and structure of foodstuffs, turning them into forms that can be eaten. Endothermic reactions, which absorb heat to activate yeast and aid in dough rising, are used in bread baking. COMMON APPLICATIONS OF THERMOCHEMISTRY METABOLISM The metabolism of the human body is a set of chemical processes that generate heat, release or absorb energy, and support physical activity. Our bodies use exothermic processes to break down proteins, lipids, and carbs when we eat, releasing energy that keeps us warm and powers our movements. COMMON APPLICATIONS OF THERMOCHEMISTRY BATTERY TECHNOLOGY Batteries, which store and release energy through chemical processes, are designed and operated in part by thermochemistry. Exothermic reactions are used by lithium-ion batteries in electric vehicles and smartphones to provide electrical energy. COMMON APPLICATIONS OF THERMOCHEMISTRY EXPLOSIVES AND FIREWORKS Exothermic reactions, which release significant quantities of energy quickly and produce heat, light, and sound, are the basis of explosives and pyrotechnics. Certain chemical compounds burn during fireworks, releasing energy in the form of loud noises and vibrant colors. HEAT is the transfer of thermal energy between two bodies that are at different temperatures as a convention, heat is represented by “q”. it implies the transfer of energy usually in absorption and release during the process.  SYSTEM AND SURROUNDING to analyze energy changes associated with chemical reactions, it is vital to know the difference between the system and the surroundings. “Universe” is the area where the constant heat energy flows. “System” is the part of the universe being studied or to which attention or energy is focused. “Surrounding” includes everything else in the universe.  TYPES OF SYSTEM Open system – can exchange mass and energy, usually in the form of heat with its surroundings. Closed system – which allows the transfer of heat energy but not mass. Isolated system – which does not allow the transfer of either mass or energy. HEAT IN A GIVEN SYSTEM ENDOTHERMIC - thermodynamic reaction or process that absorbs heat. - input of heat. - heat is supplied to the system by the surroundings. EXOTHERMIC - thermodynamic reaction or process that releases heat. - output of heat. - heat is supplied to the surroundings by the system. FIRST LAW OF THERMODYNAMICS Thermochemistry is a branch of thermodynamics, which deals with the interconversion of energy between two forms: heat and work. It is the version of the law of conservation of energy, adapted for the thermodynamic system. Activity #4 Directions: 1. Scan the provided QR code and choose the “systems” simulation. 2. Make use of every resource included in the simulation and watch how it responds to energy. 3. Keep track of your observations and respond to every question on your activity sheet. Heat in Everyday Life Can you identify which objects produce heat?  FIRST LAW OF THERMODYNAMICS It states that in any process, the change in energy of a system is equal to the heat absorbed by the system and the work done on it. It is quantified using the unit joule (J) and mathematically expressed as: U=q+w where: U = change in internal energy of the system q = heat exchange between the system and the surroundings w = work done on or by the system HEAT (q) WORK (w) THERMODYNAMIC PROCESS (U) Conventions: (+) the system absorbs (+) work is done on the system, it gains (+) endothermic heat energy process (-) the system releases (-) when the system does the work, it (-) exothermic heat uses up to transfers some of its energy process SAMPLE PROBLEM #1 A gas releases 48 J of heat as 103 J of work was done to compress it. Calculate the change in internal energy and identify the type of thermodynamic process involved. Δ𝑈 = 𝑞 + 𝑤 Δ𝑈 = −48 𝐽 + 103 𝐽 𝜟𝑼 = 𝟓𝟓 𝑱 𝑬𝒏𝒅𝒐𝒕𝒉𝒆𝒓𝒎𝒊𝒄 𝒓𝒆𝒂𝒄𝒕𝒊𝒐𝒏 SAMPLE PROBLEM #2 A gas absorbs 208 J of heat as it does 372 J of work by expanding. Calculate the change in internal energy and identify the type of thermodynamic process involved. Δ𝑈 = 𝑞 + 𝑤 Δ𝑈 = 208 𝐽 + (−372 𝐽) 𝜟𝑼 = −𝟏𝟔𝟒 𝑱 𝑬𝒙𝒐𝒕𝒉𝒆𝒓𝒎𝒊𝒄 𝒓𝒆𝒂𝒄𝒕𝒊𝒐𝒏 SAMPLE PROBLEM #3 If the change in internal energy of the system is 85.0 J, how much heat must be added to the system so that it can do work of 15.5J? Δ𝑈 = 𝑞 + 𝑤 → 𝒒 = Δ𝑼 − 𝒘 (𝑑𝑒𝑟𝑖𝑣𝑒𝑑 𝑓𝑜𝑟𝑚𝑢𝑙𝑎) 𝑞 = 𝛥𝑈 − 𝑤 𝑞 = 85.0 𝐽 − (15.5 𝐽) 𝒒 = 𝟔𝟗. 𝟓 𝑱 𝒉𝒆𝒂𝒕 𝒊𝒔 𝒂𝒅𝒅𝒆𝒅 𝒕𝒐 𝒕𝒉𝒆 𝒔𝒚𝒔𝒕𝒆𝒎 SAMPLE PROBLEM #4 Suppose that you run through a 50-meter distance, and you performed 2 kJ of work. If, before running, you eat food from which you obtain 800 J, would this activity cause your weight to increase or decrease? Δ𝑈 = 𝑞 + 𝑤 Δ𝑈 = 800 𝐽 + (−2000 𝐽) 𝜟𝑼 = −𝟏, 𝟐𝟎𝟎 𝑱 𝑬𝒙𝒐𝒕𝒉𝒆𝒓𝒎𝒊𝒄 𝒓𝒆𝒂𝒄𝒕𝒊𝒐𝒏 SAMPLE PROBLEM #5 A gas sample in a vessel has an internal energy of -1420 J. If 250 J of heat is added in the system, calculate the work done by the gas sample. Δ𝑈 = 𝑞 + 𝑤 → Δ𝑼 − 𝒒 = 𝒘 (𝑑𝑒𝑟𝑖𝑣𝑒𝑑 𝑓𝑜𝑟𝑚𝑢𝑙𝑎) 𝑤 = Δ𝑈 − 𝑞 𝑤 = −1420 𝐽 − 250 𝐽 𝒘 = −𝟏, 𝟔𝟕𝟎 𝑱 𝑾𝒐𝒓𝒌 𝒊𝒔 𝒅𝒐𝒏𝒆 𝑩𝒀 𝒕𝒉𝒆 𝒔𝒚𝒔𝒕𝒆𝒎 ACTIVITY #5: PRACTICE EXERCISES Directions: Read and analyze each of the following word problems. On your activity sheet, respond to it using the GRESA (Given, Required, Equation, Solution, and Answer) method. The work done when a gas is compressed in a cylinder is 462 J. During the process, there is a heat transfer of 128 J from the gas to the surroundings. Calculate the change in internal energy and identify the type of thermodynamic process involved. Suppose there is a heat transfer of 48.00 J to a system, while the system does 21.50 J of work. Calculate the change in internal energy and identify the type of thermodynamic process involved.  CALORIMETRY the word calorimetry is derived from the Latin word calor, meaning heat, and the Greek word metron, meaning measure. it is performed using calorimeter. The world’s first ice-calorimeter, used in the winter of 1782–83, by Antoine Lavoisier and Pierre-Simon Laplace, to determine the heat involved in various chemical changes; calculations which were based on Joseph Black’s prior discovery of latent heat. These experiments mark the foundation of thermochemistry. In calorimetry, The amount of heat absorbed or released by the system is a function of its temperature change. 𝜟q=C𝜟T 𝜟 T = TF – Ti From the equation, Q and T changes are related by a proportionality constant referred to as heat capacity (C). This constant is expressed in the units J/0C and is considered as extensive property. The heat capacity of a substance can only be determined experimentally through calorimetry. For a pure substance, the heat capacity is equal to the product of its mass and specific heat. C = mc C = heat capacity m = mass C = specific heat  SPECIFIC HEAT The specific heat (c) of a substance is the amount of heat required to raise the temperature of one gram of the substance by one degree Celsius. It is an example of intensive property. 𝑱 Substance Specific Heat It has the units ˚𝑪 Al 0.900 𝒈 Au 0.129 C (graphite) 0.720 C (diamond) 0.502 Cu 0.385 Fe 0.444 Hg 0.139 Pb 0.158 H2O(s) 2.11 H2O(l) 4.18 H2O(g) 2.08 C2H5OH 2.46 Therefore, the formula will be q = mc T Heat Capacity & Specific Heat Heat Capacity, C ability of a substance or to absorb heat energy without significantly changing its temperature Mathematical formula: 𝒒=C𝜟T Unit: J/°C Specific heat Capacity, c measure of the amount of heat energy required to raise the temperature of a unit mass (1 g or 1 kg) of a substance by 1°C or K Mathematical formula: 𝒒 = 𝒎𝒄𝜟T Unit: J/g°C Derivation of formula: q = mc∆T H2O 𝑞 𝒎𝑐∆𝑇 𝑞 m=? 𝑐∆𝑇 = 𝑐∆𝑇 𝑚= 𝑐∆ 𝑞 𝑚𝒄∆𝑇 𝑞 c=? = 𝑐= 𝑚∆ 𝑚∆𝑇 𝑚∆𝑇 𝒒 𝒎𝒄∆𝑻 𝑞 ∆T = ? = ∆𝑇 = 𝒎𝒄 𝒎𝒄 𝑚𝑐 Derivation of formula 𝑇𝑓 = ? q = mc∆T H2O 𝑞 = 𝑚𝑐∆𝑇 𝑞 = 𝑚𝑐(𝑇𝑓 − 𝑇𝑖 ) 𝑞 + 𝑇𝑖 = 𝑇𝑓 𝑞 = 𝑚𝑐(𝑇𝑓 − 𝑇𝑖 ) 𝑚𝑐 𝑚𝑐 𝑚𝑐 𝑞 𝑞 𝑇𝑖 + = 𝑇𝑓 = 𝑇𝑓 − 𝑇𝑖 𝑚𝑐 𝑚𝑐 Derivation of formula: 𝑇𝑖 = ? q = mc∆T H2O 𝑞 = 𝑚𝑐∆𝑇 𝑞 𝑞 = 𝑚𝑐(𝑇𝑓 − 𝑇𝑖 ) − 𝑇𝑓 = −𝑇𝑖 𝑚𝑐 𝑞 = 𝑚𝑐(𝑇𝑓 − 𝑇𝑖 ) 𝑞 𝑚𝑐 𝑚𝑐 − + 𝑇𝑓 = 𝑇𝑖 𝑚𝑐 𝑞 𝑞 = 𝑇𝑓 − 𝑇𝑖 𝑇𝑓 − = 𝑇𝑖 𝑚𝑐 𝑚𝑐  SAMPLE PROBLEM How much energy is required to heat 80 grams of water from 26oC to 48oC? The specific heat capacity of water is 4.184 J/goC. Given: Solution: mH O = 80 g c = 4.184 J/goC ∆ T = (48.0℃ - 26.0℃ ) = 22.0℃ 2 Ti = 26.0oC Tf = 48.0oC q = mc∆T 𝐽 Required: qH2O = J? = (80 g) x (4.184 ) x 22.0℃ 𝑔𝑥℃ Formula: qH2O = mc∆T Answer: qH2O = 7363.84 J SAMPLE PROBLEM #1 How much heat is absorbed by liquid water that weighs 720g as it is heated from 35 C to 0 1100C? 𝑞 = 𝑚𝑐∆T 𝑞 = 𝑚𝑐 𝑇𝑓 − 𝑇𝑖 𝐽 𝑞 = 720 𝑔 4.18 (110˚𝐶 − 35˚𝐶) 𝑔˚𝐶 𝐽 𝑞 = 720 𝑔 4.18 (75˚𝐶) 𝑔˚𝐶 𝒒 = 𝟐𝟐𝟓, 𝟕𝟐𝟎 𝑱 𝒐𝒓 𝟐. 𝟑𝒙𝟏𝟎𝟓 𝑱 ENDOTHERMIC REACTION SAMPLE PROBLEM #2 How much heat is released by an 87-gram piece of copper as it cools from 835 C to 411 C? 0 0 𝑞 = 𝑚𝑐∆T 𝑞 = 𝑚𝑐 𝑇𝑓 − 𝑇𝑖 𝐽 𝑞 = 87𝑔 0.385 (411˚𝐶 − 835˚𝐶) 𝑔˚𝐶 𝐽 𝑞 = 87 𝑔 0.385 (−424˚𝐶) 𝑔˚𝐶 𝟒 𝒒 = −𝟏𝟒, 𝟐𝟎𝟏. 𝟖𝟖 𝑱 𝒐𝒓 − 𝟏. 𝟒𝒙𝟏𝟎 𝑱 EXOTHERMIC REACTION ACTIVITY #6: PRACTICE EXERCISES Directions: Read and analyze each of the following word problems. On your activity sheet, respond to it using the GRESA (Given, Required, Equation, Solution, and Answer) method. A 25-g metal sample absorbed 211 J of heat as it was heated from 32 C to 98.5 C. What is the 0 0 specific heat of the metal? How much heat is released by 920 g of solid water as it is heated from 870C to 120C?