Chapter 3- UNIT 1 - ENERGY AND ITS CONVERSION

Energy

Ability to do work

work (w)

displacement of an object against an opposing force

4 types of energy

1. KE

2. PE

3. Thermal energy

4. Radiant energy

types of PE

electrical

chemical

mass

KE

energy an object has cuz its moving

dependent on velocity and mass of object

SI unit= kg m²s²- referred to as joules (J)

KE formula

Ekinetic = ½ mv²

PE

stored energy an object has cuz its position/ configuration due to working against natural forces (gravity, elasticity, electrostatic forces)

THINK: POTENTIALLY able to do smth in future

gravitational PE

Energy stored in an object because of its position or height in a gravitational field.

ex. as rock falls off a ledge= change to KE

electrical PE

stored energy associated with positions of electrical charges relative to one another

as opp charges move closer= energy RELEASED

as opp charges move further= energy must be SUPPLIED to seperate

k (in Eelectrical)

k tells you how strong the electrostatic force is for given charges and distance.

what must be done to remove e- from atoms or molecules ?

energy must be applied to overcome this electrical energy

chemical energy

“bond energy”

form of PE stored in arrangement of atoms within molecules

originates from electrical forces between (-) charge e- and (+) charged nuclei

what does breaking bonds require and why?

energy input to overcome attractive forces

what does forming bonds do and why?

releases energy cuz system moves to a more stable, lower energy arrangement

mass (mass PE)

transformation of mass energy energy

e=mc²

source of energy released in nuclear reactions

thermal energy

energy object has due to random motion of its particles

molecules possess dif forms of thermal energy

dif forms of thermal energy

• Translational motion → movement of the entire molecule from one location to another.

• Rotational motion → rotation of the molecule around an axis.

• Vibrational motion → repeated movement of atoms within a molecule relative to each other, such as stretching or bending bonds.

ex. h2o molecule can vibrate cuz of internal motion of its atoms and has rotational energy

radiant energy

energy that travels through space as EM waves (light, infrared, radiowaves, x-rays)

energy transformations

energy can be transformed from 1 type to another

energy transformations accompany chemical reactions

energy transfers

movement of energy from one object to another

system

the study itself

surroundings

everything else but the system

boundary

what seperates system from surroundings

conservation of energy

energy is neither created or destroyed but may be transferred from one object to another

OR

transformed from one form to another

what can energy be transferred as?

work or heat but NO energy can be lost, nor can heat or work be obtained from nothing

can a system exchange energy with its surrounding?

yes like thermal energy, work, radiant energy

heat (q)

energy in transfer between a system and its surroundings

measured in joules (J)

chemical reactions and heat flow

chemical reactions result in heat flows

reaction releases energy= released energy may flow from chemical system to its surroundings

reaction absorbs energy= allowing heat from surroundings to system

exothermic

release energy

transfers heat from system to surroundings

endothermic

absorb energy

transfers heat from surroundings to system

what 4 factors does the magnitude of ▲T depend on?

1. # of heat transferred (q)- more heat= larger ▲T

2. direction of heat flow: heat absorbed= (+) ▲T vice versa

3. # of material (n): ▲T= inversely related to # of absorbance

4. identity of material (molar heat capacity ( Cm ) ) : dif substances respond differently to same heat input

specific heat capacity

# of heat required to raise temp of 1g of substance by 1°C

heat transferred = q=mCs▲T

molar heat capacity

# of heat needed to raise temp of 1mol of susbtance by 1°C (J/ mol °C)

heat transferred = q= nCm▲T

work

energy used to move a object against opposing force

flow of energy between objects or between a chemical system and its surrounding

work on system

sign of (w) is (-) cuz system loses energy

work on surroundings

(w) is (+) cuz system gains energy

what do electrical forces lead to?

electrical potential energy

(ex. moving an e- further away from its nucleus increases the electrical PE)

internal energy (U)

sum of kinetic and potential energies of all the particles that compose a system

can increase or decrease through heat transfer (q) or work (w)

energy vs heat and work

energy= smth that an object possesses and is a STATE FUNCTION

heat and work= objects that exchange energy

what are energies of molecular vibrations combinations of?

KE and PE

how do translational, rotational, vibrational energies of molecules increase?

with temperature and are apart of total thermal energy of gas

ex. (raise temp (effect), raise thermal energy(cause) )

state function

properties that depend only on conditions that describe the system before and after transformation

depends only on STARTING and ENDING point

path functions

properties that depend on how the change occurs/ takes place

ex. heat (q) and work (w) are PATH FUNCTIONS

constant pressure

system or process where external force per unit area acting on a boundary remains unchanged throughout a reaction or physical change