definitions Flashcards
define absolute humidity
the mas of water vapour present in a sample of air at a given temp. measured in kg/m3
define absolute zero
the coldest possible temperature, where nothing can be colder and where all thermal motion stops.
0 kelvins or - 273.15 degrees C
define an ampere
SI base unit of electrical current
current that produces a force of 2x 10^-7 N per meter between 2 wires of infinite length (negligible cross section) that are 1 meter apart in a vacuum.
( …. current flow through a conductor will induce an magnetic field. If two conductors are close to each other they will attract/repel each other, So the current needed to produce a certain electromagnetic force between two conductors one metre apart.)
ampere is amount of electrical charge passing a point per unit time
equivalent to 6.24x10^18 electrons (1 coloumb) per second
define boiling point
the temperature at which the vapour pressure of a liquid equals the surrounding ambient temperature and the liquid turns into a gas.
define calorie…
the amount of energy needed to rise 1g of water by 1 degree C
1 calorie = 4.18 joules
define candela …
the SI base unit for luminosity intensity
1 cd is the luminous intensity in a given direction of a source that emits
monochromatic radiation
of frequency 5.4 × 10^14 hertz
And that has a radiant intensity in that direction of 1/683 watt per square radian (steradian).
define coulomb …
unit of charge
1 coulomb is the amount of charge passing 1 point per second when 1 amp of current is applied.
1C = 1A x 1s
equivalent to 6.24 x 10^18 electrons
define critical temperature…
the temperature above which a gas cannot be liquified by increasing pressure
define freezing point…
the temp at which the liquid and solid phases of a substance are in equilibrium at a given pressure.
define force…
A force is an influence that changes an objects state of rest or motion
1 Newton is the force required to accelerate 1kg by 1m/s^2
force has both magnitude and direction, making it a vector.
define gas…
One of the four fundamental states of matter found between the liquid
and plasma phase (four states = solid, liquid, gas and plasma)
a substance which is above its critical temperature
particles within a gas are vastly separated, space between atoms/molecules is larger than the atom/molecule itself.
a gas will expand to fill any space.
define heat capacity…
the amount of heat required to raise the temperature of an object by 1 degree C
SI unit = joule/kelvin
what equation relates force to accelaration?
F=ma
how is specific heat capacity turned into heat capacity?
specific heat capacity of an object x mass = heat capacity
define Hertz…
SI unit for frequency
1 Hertz = 1 cycle per second
define joule
1 Joule is the work done when 1 newton of force is applied over 1 meter of distance to an object
SI unit for energy
define kelvin
SI base unit for temperature
1 K is equal to 1/273.16 of the thermodynamic scale temperature of the triple point of water (0.01 degrees C)
The Kelvin scale is an absolute thermodynamic temperature scale, using absolute zero as its null point.
define kilogram
SI base unit for mass
The standard kilogram is the mass of a cylindrical piece of platinum iridium alloy kept in Sèvres, france
define kinetic energy…
the energy an object posses because of its motion
It is defined as the energy needed to accelerate the object from a state
of rest to its given velocity. This energy is equal to the work it would do
when decelerating to return to rest
define latent heat…
The energy released or absorbed by a substance when it changes phase
at a given temperature, e.g. ice melting
define specific latent heat of fusion…
the amount of heat required to convert a unit mass of solid at its melting point to a liquid without any increase in temperature at a given pressure.
define specific latent heat of vapourisation…
the amount of heat required to convert a unit mass of liquid at its boiling point to a vapour without an increase in temperature at a given pressure
define mass…
the amount of matter contained in a body.
The SI unit for this is Kg
Unlike weight, mass does not alter under conditions of differing gravity.
define meter…
SI base unit for length
defined as the length of the path travelled by light in vacuum
during the time interval of 1/300 000 000th of a second.
define mole…
SI base unit for amount of substance
Quantity containing the same number of particles as there are atoms
in 12 g of carbon-12. This number of particles is 6.022 × 1023 and is
known as Avogadro’s constant.
what is the equation for momentum?
mass x velocity
what is the definition of a newton?
SI derived unit for force
1 N is the force required to accelerate a mass of 1kg by 1m per second
squared.
define an Ohm?
derived SI unit for electrical resistance
1 ohm is the resistance between two points of a conductor when a
constant potential difference of 1 volt applied between them produces a
current of 1 ampere
define pascal…
derived SI unit for pressure
1Pa is the force of 1 N acting over 1m2
define pH…
a measure of acidity
negative logathitm to the base 10 of H+ concentration in a solution
-log10 [H+]
define potential energy..
The energy of a body or system as a result of its position in an electric,
magnetic or gravitational field. It is the potential of that body to do work.
define power…
the rate of doing work.
unit = watts
1 watt = 1 joules/ sec
define pressure
force per unit area
units pascal
define relative humidity…
The mass of water in a given volume of air, expressed as a percentage
of the maximum mass of water that the air could hold at the given
temperature.
The ratio of the water vapour pressure to the saturated vapour pressure
define resistance
The opposition of flow e.g electrical current or fluid
The derived SI unit of electrical resistance is the Ohm (Ω)
define saturated vapour pressure…
The pressure exerted by a vapour when in contact with and in equilibrium
with its liquid phase within a closed system at a given temperature.
define a second..
SI base unit for time
Defined according to the frequency of radiation emitted by caesium-133
in its ground state.
One second =around 9 billion oscillations of a Caesium 133 atomic clock.
define specific heat capacity
The amount of energy required to raise the temperature of 1kg of a
substance by 1°C
what is the specific heat capacity of water and the human body?
> SHC of water = 4.16 kJ/kg °C
SHC of human body = 3.5 kJ/kg °C
define the triple point of water?
The temperature and pressure at which water exists in equilibrium as
liquid water, solid ice and water vapour
Temperature = 0.01°C or 273.16 K, pressure = 0.006 atmosphere or
611.73 pascals
define vapour…
A substance in the gas phase below its critical temperature.
define a volt…
related to joules and coloumbs, amps and wats, amps and ohms
Derived SI unit of electrical potential
1volt is the potential difference between two points of a conducting wire
when 1joule of work is done to move 1coulomb of charge between them
Joules / coulomb or V=W/A
define a watt…
SI derived unit for power
1 joule per second
define weight…
The gravitational force acting on an object. Measured in newtons
Weight = mass in kg × gravitational acceleration (9.81ms–2). A mass of
1kg will therefore have 9.81 N acting on it on the surface of the earth
what is the value for gravitational accelaration?
9.81m/s^2
define work and energy
work done done is the energy used to push a force (N) by a certain distance (m)
as work done is the energy used, it is also measured in joules.
energy is the capacity/potential to do work. also measured in joules.
energy can be potential or kinetic - potential is to do with its position and kinetic is to do with an objects motion.
define newtons first law
a body will remain either at rest or constant velocity if no net force is acting upon it.
define newtons second law
F= MA
I.E. To accelerate double the mass at the same rate, double the force is required
define newtons 3rd law
For every action, there is an equal and opposite reaction
If a weight applies 10N of force to the ground, the ground applies 10N of force upwards to the weight
what is inertia?
the tendancy of an object to resist changes in state of motion unless a net force acts upon it.
what does 1% solution of drug mean?
A 1% solution therefore is made up of 1% drug, and 99% solvent and additives
i.e. 10g/1L or 1g/100ml or 10mg/ml
how is degree C converted to kelvin?
degrees + 273.15 = kelvin
