# Ch. 6 APCHEM (Thermochemistry

## 39 terms

### Kinetic Energy

The mechanical energy that a body has by virtue of its motion

### Intensive Property

A property that depends on the type of matter in a sample, not the amount of matter, density, redox , electrolysis

### Atmospheric Pressure

the pressure exerted by the atmosphere on all objects within it, , results from the collisions of atoms and molecules in air with objects

### Barometer

an instrument used to measure atmospheric pressure, 760 = 1 ATM

### Energy

the capacity of a physical system to do work or produce heat, measured in joules or Newton-meters.

### Standard State

For a pure substance, the most stable form of the substance at 1 atm and a specified temperature, usually 25°C: for a gas, 1 atm; for a solution, concentration of 1 molar.

### Potential Energy

Energy stored due to an object's position or arrangement For Example: Attractive and Repulsive Forces within atom.

### Temperature

A measure of the average energy of motion of the particles of a substance.

### Law of Conservation of Energy

The first law of thermodynamics, , the law that states that energy cannot be created or destroyed but can be changed from one form to another (Energy of Universe is Constant) KE= 1/2 mv^2

### Frictional heating

Explains why when heat is transferred because of friction (i.e. when a ball rolls down a hill, some of its kinetic energy is given to the hill), and temperature of the hill will increase slighlty.

### Heat

The TRANSFER of energy between objects due to a TEMPERATURE difference, always from hotest to coldest.(NOT contained by an object), depends on the pathway.

### Work

Defined as force acting over distance. One of the ways along with heat that enerfy can be transfered, however this depends on the pathway.

### Pathway

The way in which energy transfer is divided between work and heat.

### State Function

Also called the state property,, property of the system that changes independently of its pathway (only depends on CURRENT state), Elavation, Enthalpy, and ENERGY are examples, however DISTANCE, WORK, AND HEAT are not.

### System

Part of the universe in which we focus our attention. The reactants and Products of a reaction

### Surroundings

Everything in the universe accept the sytem (our focus)

### Exothermic

A description of a change in which a system releases energy to its surroundings, depends on potential energy differences bonds in the products(on average are stronger) then the reactants bonds(higher potential enrgy), hot to the touch

### Endothermic

A description of a change in which a system absorbs energy from its surroundings,depends on potential energy differences , products(higher potential enregy) and are weaker then reactants bonds(on average), cold to the touch Example Formation of NO(nitric oxide)

### Thermal Energy

Total amount of energy associated with the random movement of atoms and molecules (Temperature) in a sample of matter is converted by a exothermic reaction via heat.

### Internal Energy

E, the sum of the Kinetic and Potential Energy of a system. E= q+w, where q represents heat and w represents work

### Number

One of the two parts of thermodynamic quantities, represents the magnitude.

### Sign

One of the two parts of thermodynamic quantities, represents the direction of the flow(in the systems point of view) q = - for exothermic and, q= + for endothermic reactions, but also applys work

### Expansion

work done by a gas through a chemical process is frequently called __________

### Compression

Work done to a gas through a process is frequently called ______________

### Pressure

Defined as Force over area (Pg. 233), makes W= Force times change in (h) or distance or -pressure x changee in height. Always refers to external pressure.

### Change in volume

Equals Final volume - Initial Volume = A times change in (h)

### Enthalpy

H = E +PV, a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure, state function

### Heat of Reaction

the enthalpy change for the chemical equation exactly as it is written

### Specific Heat Capacity

the amount of heat energy required to raise the temperature of one gram of substance by one degree celcius

### Molar Heat Capacity

the energy required to raise the temperature of one mole of a substance by one degree Celsius

### Calorimetry

the precise measurement of the heat flow into or out of a system for chemical and physical processes

### calorimeter

an insulated device used to measure the absorption or release of heat in chemical or physical processes

### Heat Capacity

The amount of heat required to raise the temperature of a specified amount of a substance by 1°C or 1 K.

### Constant Pressure Calorimetry

the measurement of heat using a simple calorimeter to determine the changes in enthalpy for reactions occurring in solution; the pressure (atmospheric pressure) remains constant during the process.

### Extensive Property

a property that depends on the amount of matter in a sample

### Constant volume Calorimetry

the measurement of heat at a constant volume to find the change in internal energy of the system, requires the use of a "bomb" colorimeter

### Hess's Law

enthalpy change for a reaction depends only on the difference between the enthalpy of the products and the enthalpy of the reactants.

### Standard enthalpy of formation

the enthalpy change that accompanies the formation of one mole of a compound at 25 C from its elements, with all substances in their standard states at that temperature

### Synthesis Reaction

a chemical reaction in which two or more substances react to yield a single product

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