Thermochemistry

• Thermodynamics is the science of the relationships between heat and other forms of energy.
• Thermochemistry is the study of the quantity of heat absorbed or given off by chemical reactions.
• Knowing the quantity of heat can calculate the amount of energy needed to break a particular kind of chemical bond to learn about the strength of that bond and to determine whether a particular chemical reaction occurs and, if so, to what extent.
• Energy is the potential or capacity to move matter.
• Kinetic energy is the energy associated with an object by its motion.
• Ek= 1/2mv^2 is that the formula shows that the kinetic energy of an object depends on both its mass and its speed.
• The calorie is a non-SI unit of energy commonly used by chemists, originally defined as the amount of energy required to raise the temperature of one gram of water by one degree Celsius.
• Potential energy is the energy an object has by its position in a field of force.
• Ep = mgh
• Internal energy (U) is the sum of kinetic energy and potential energy of particles making up a substance.
• The law of conservation of energy states that energy may be converted from one form to another, but the total quantity of energy remains constant.
• A thermodynamic system is a substance or mixture of substances in which a change occurs.
• Everything outside the thermodynamic system is called surroundings.
• Work is an energy transfer into or out of a thermodynamic system whose effect on the surroundings is equivalent to moving an object through a field of force.
• When work is done on the thermodynamic system it's positive and when work is done by the thermodynamic system it's negative.
• Heat is an energy transfer into or out of a thermodynamic system that results from a temperature difference between the system and its surroundings.
• Heat flows from a region of higher temperature to one of lower temperature.
• A state function is a property of a system that depends only on its present state, which is determined by variables such as temperature and pressure and which is independent of any previous history of the system.
• The first law of thermodynamics is the change in the internal energy of a system equals heat plus work.
• The heat of reaction is the heat, q, absorbed or evolved from a reaction system to retain a fixed temperature of the system under the conditions specified for the reaction.
• An exothermic process is a chemical reaction or a physical change in which heat is released (q is negative).
• An endothermic process is a chemical reaction or a physical change in which heat is absorbed (q is positive).
• The enthalpy of a thermodynamic system is defined as its internal energy plus pressure times volume.
• The thermochemical equation is the chemical equation for a reaction in which the equation is given a molar interpretation, and the enthalpy of the reaction for these molar amounts is written directly after the equation.
• The heat capacity (C) of a substance is the quantity of heat needed to raise the temperature of a substance one degree Celsius (or one kelvin).
• The molar heat capacity of a substance is its heat capacity for one mole of a substance.
• The specific heat capacity is the quantity of heat required to raise the temperature of one gram of a substance by one degree at a constant temperature.
• A calorimeter is a device used to measure the heat absorbed or evolved during a physical or chemical change.
• Hess’s law of heat summation states that for a chemical equation written as the sum of two or more steps, the enthalpy change for the overall equation equals the sum of the enthalpy changes for the individual steps.
• Standard state refers to the standard thermodynamic conditions chosen for substances when listing or comparing thermodynamic data: 1 atm pressure and the specified temperature.
• An allotrope is one of two or more distinct forms of an element in the same physical state.
• The reference form of an element to specify the formation reaction is usually the stablest form (physical state and allotrope) of the element under standard thermodynamic conditions.
• The standard enthalpy of formation (also called the standard heat of formation) of a substance, denoted DH8f, is the enthalpy change for the formation of one mole of the substance in its standard state from its elements in their reference form and in their standard states.
• A change of a substance from one state to another is called a change of state or phase transition
• Melting is the change of a solid to a liquid state (melting is also referred to as fusion)
• Freezing is the change of a liquid to a solid state.
• Vaporization is the change of a solid or a liquid to the vapour.
• The change of a solid directly to the vapour is specifically referred to as sublimation.
• Condensation is the change of a gas to either the liquid or the solid state (the change of vapor to solid is sometimes called deposition)
• Dew is liquid water formed by condensation of water vapour from the atmosphere.