energy, systems, units (intro) Flashcards
(26 cards)
what is energy?
ability to do work or transfer heat
2 ways to describe energy?
work and heat
what is work? what variable do we use for work?
work = energy used to cause an object that has mass to move
denoted by w
what is heat? what variable used for heat?
heat= energy used to change the temperature of an object
denoted by q
in reactions, heat can be ___ or ___
released or absorbed
describe the flow of heat= always flows from __ to ___ objects
from HOT to COLD objects
how is energy transferred between objects?
through physical contact!
what is kinetic energy?
energy object possesses by virtue of its motion
what is thermal kinetic energy?
energy of a system due to the movement of its atoms/molecules
kinetic energy is directly proportional to ___? explain
speed/velocity!
faster movt of atoms = more friction with surroundings = generates more heat!
thermal kinetic energy is associated with ___
temperature
what is potential energy?
energy object possesses by virtue of its POSITION or CHEMICAL COMPOSITION (ex. gravity, energy stored in bonds)
what is chemical potential energy?
energy stored in the chemical bonds of atoms/molecules
combustion reactions always produce ___. products will have ___ potential energy than the reactants here. why?
heat!
less potential energy than reactants, bc some energy is lost as heat!
what is elastic potential energy?
energy stored in objects that are compressed or stretched
what is a system?
all defined matter/energy involved in the problem at hand (ex. chemical reaction)
what is surroundings?
everything outside of the system (house, city, the world basically)
what is the universe?
the system + surroundings
what is an open system? closed system? isolated system?
open = both matter and energy can be transferred to surroundings (ex. open beaker)
closed= only energy can be transferred to surroundings, NOT matter
isolated = neither matter nor energy can be transferred to surroundings (ex. closed thermos)
1st law of thermodynamics?
energy cannot be created or destroyed, only converted from one form to another or transferred.
total energy of the universe is ___
finite
delta symbol used to denote __?
“change in” or “final - initial”
ΔE system and Δsurroundings is ___ and ___.
thus, the ΔE universe = ___?
equal and opposite!
ΔE universe = 0!!
what is a joule?
SI unit for energy. amount of energy needed to accelerate 1 kg object by 1 meter
defined as 1 kg x m^2/s^2
