Lecture 12 Chapter 6th
6. 1 Thermochemistry: Energy & units (p. 227)
From observation we know, that
-- some chemical reactions begin when the reactants touch each other (precipitation reactions)
-- some reactions are gradual or even therefore slow by room heat that even lifetime can be not enough to see a measurable change (rusting of straightener, tarnishing silver) Also, nearly all chemical reactions require exchange of warmth (or energy): in combustion reactions lot of heat is usually released
in neutralization reactions and others.
Copy of heat is known as a major theme of thermodynamics, the science of heat exchange (or energy exchange).
Queen: Why it is vital to know the amount of heat (energy) involved in a chemical reaction?
Response: when chemical reaction takes place the rearrangement of atoms occurs and some provides have to be damaged (energy is definitely needed) and new bonds form (energy is released) we can purchase strength with the bonds, we could also foresee whether the effect will arise.
Q: How to define strength? or What is energy?
Strength is ability to do work. (or ability to do work)
Contrary to matter, energy is known and recognized by its effect. It cannot be seen, touched, smelled, or acessed.
Different forms of energy:
Kinetic energy, Ek: energy associated with the moving target, it can be worked out, if we know the dimensions of the mass associated with an object and it acceleration or speed Ek = m a huge selection of units of energy: kg back button m2/s2 is known as joule (J) Examples of kinetic energy:
strength of shifting baseball
electricty of electrons moving by using a conductor
bright energy through the sun
heat energy of atoms, elements, or ions at the submicroscopic level Kinetic energy is often expressed by common unit of energy, that is certainly by calorie (cal)
you calorie is the amount of energy needed to enhance the temperature of one gram of water, INGESTING WATER, by one particular oC.
you cal sama dengan 4. 184 J
Potential energy, Ep: energy which will result from an object's placement in a discipline of force. Is often termed as stored strength. Examples:
chemical substance potential energy of electrons and atomic nuclei in molecules gravitational energy (Ep = meters x g x h) as for a ball organised above the floor or desk electrostatic strength between confident and bad ions a tiny distance separate chemical energy stored inside the structured devices of chemical substances (when the chemical reaction arises, chemical strength is introduced, stored, or converted to other designs of energy
Interior energy, (U): the quantity of kinetic and potential energy of the subatomic allergens (electrons and nuclei) creating the element. So , the total energy of a specific quantity of element is
Etot = Ek + Ep + U
When a compound is at relax (not moving): Ek = 0 If a substance is at constant level (on the table) Ep = zero So , Etot = U internal strength (any material object has internal energy)
Energy can easily neither be created neither destroyed; the whole energy of the universe is definitely constant.
Legislation of conservation of energy
Energy can be transformed from one kind to another, but the total amount of energy remains constant.
6th. 2 First Law of Thermodynamics; Function & Warmth (p. 230)
In thermodynamic processes (processes that involve the heat or perhaps energy flow) we deal with the system and the surrounding. The machine is the material or blend of substances in which a change occurs. The surrounding is everything outside the system.
For example: if we study the response between A and W (in a solution) the reaction mixture is a system, as well as the beaker (reaction vessel), air above the answer and outside the beaker is known as a surrounding. ( see Fig. 6. four p. 230)
Almost all chemical reactions absorb or release (produce) energy by means of heat.
Heat is the copy of thermal energy among two body that are in different conditions.
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