Terms SAS 7-13

• Solution: A homogeneous mixture of two or more substances
• Solute: The substance that is dissolved in a solution
• Solvent: The component present in greater quantity in a solution, determining its state of matter
• Concentration is the amount of solute in a solution or solvent
• Percent by mass is a way to compute the concentration of a solution based on the mass of the solute compared to the total mass of the solution
• Percent by volume is a method to calculate the concentration of a solution by comparing the volume of the solute to the total volume of the solution
• Exothermic processes: Forming a chemical bond releases energy and is a heat-releasing process
• Exothermic reactions usually feel hot because they give off heat
• Endothermic processes: Breaking a chemical bond requires energy and is a heat-absorbing process
• Endothermic reactions usually feel cold because they absorb heat from the surroundings
• Exothermic- the word describes a process that releases energy in the form of heat.
• Endothermic - a process or reaction that absorbs energy in the form of heat.
• First Law of Thermodynamics: Energy can be converted from one form to another with the interaction of heat, work and internal energy, but it cannot be created nor destroyed, under any circumstances
• AU (ΔU): Total change in internal energy of a system
• q is Heat exchanged between a system and its surroundings
• W is woke done by or on the system
• Q is the contribution from heat

  : is positive when heat is absorbed out of the system (ie. heating it).

  Q is negative when heat leaks out of the system (ie. cooling it).
• W is the contribution from work.

  W is positive when work is done on the system (ie. compression).

  W is negative when work is done by the system (ie. expansion)
• Heat Flow is the transfer of thermal energy from one substance to another due to a temperature difference
• Calorimetry is the science of measuring heat flow in a chemical reaction or physical process
• Specific Heat is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius
• Symbol q represents the total heat flow in a system
• Symbol m represents the mass of the substance involved in the heat flow
• Symbol C represents the specific heat capacity of the substance
• Symbol ΔT represents the change in temperature of the substance
• Conversion factor: 4.184 Joules = 1 calorie
• Specific heat capacities:

  • Water (l): 4.184 J/g degree c
  • Water (s) (ice): 2.03 J/g degree c
  • Water (v): 2.0 J/g degree c
  • Aluminum (s): 0.89 J/g degree c
  • Iron (s): 0.45 J/g degree c
  • Mercury (l): 0.14 J/g degree c
  • Carbon (s): 0.71 J/g degree c
  • Silver (s): 0.24 J/g degree c
  • Gold (s): 0.13 J/g degree c
• Reaction Kinetics is the study of the rate of chemical reactions, which can vary greatly over different time scales
• Reaction Rates refer to the speed at which chemical reactions occur, ranging from explosively fast rates to sluggish rates over many years
• Collision Theory states that reactions happen when reactant molecules effectively collide, requiring correct spatial orientation for bond breaking and forming, and atom rearrangement to produce product molecules
• Increasing the concentration of reactants leads to more collisions, often increasing the reaction rate
• Reaction rate in heterogeneous mixtures is influenced by the surface area available for collisions
• Higher temperatures increase the rate of reaction by raising the kinetic energy of reactant molecules
• A catalyst is a substance that speeds up reactions without being consumed, providing an alternate pathway to products
• 1. Activation energy: During a molecular collision, molecules must also possess a minimum amount of kinetic energy for an effective collision to occur. This energy varies for each reaction, and is known as the ______ (Ea) (Figure 4 "Potential Energy and Activation Energy").
• 1. Rate of reaction: The ______ depends on the activation energy; a higher activation energy means that fewer molecules will have sufficient energy to undergo an effective collision.
• Collision Theory states that molecules must collide in order to react and these collisions must have sufficient energy to break chemical bonds, known as activation energy
• Activation Energy is the energy required for a reaction to occur, where higher temperatures lead to faster and more vigorous collisions between molecules
• Elementary Bimolecular Reaction involves two molecules, A and B, where collisions between them must be forceful enough to break chemical bonds
• The rate of collisions between molecules is proportional to the concentration of each gas involved in the reaction, known as Frequency of Collisions