Lectures 1-7 Flashcards
SI units
Used to standardise quantities used to measure physical properties including time, lengths, depth, mass, time, and energy. SI units help us communicate in a consistent universal way.
Common SI units
Length metre m
Mass kilogram kg
Time second s
Electric current ampere A
Temperature kelvin K
Amount of substance mole mol
Luminous intensity candela cd
Derived quantities
combinations of SI units for example;
Speed = metre per second = m/s
Prefixes
Extremely large or extremely small numbers
Common prefixes
Giga G 10^9
Mega 10^6
Kilo 10^3
Centi 10^-2
Milli 10^-3
Micro 10^-6
Nano 10^-9
Scientific notation
expressing number to the power of 10
for example;
1,000 = 1x10^3
3,000 = 3 x10^3
40,000 = 4 x 10^4
Combining units with scientific notation
Every answer you give in physics needs units
The speed of light = 3.00 x 10^8 m/s
Significant figure
indicate the precision of a number/measurement
non-zero numbers
123 has 3 significant figures
zeros between non-zero numbers
1002 has 4 significant figures
leading zeros
0.00045 has 2 significant figures
trailing zeros (if there’s a decimal place then yes if no decimal place then no)
50.0 has 3 significant figures
500 has 1 significant figure
exact numbers
counted items such as “3 apples” has an infinite number of significant figures as it is not measured but counted
why significant figures are important
more precise measurements
12m is less accurate than 12.00m
Rule for multiplying/dividing
the answer should have the same amount of significant figures as the one with the SMALLEST significant figures.
3.2 x 4.56 =14.6
Rule for adding/subtracting
The answer should have the same amount of decimal places as the one with the SMALLEST amount of decimal places.
12.34 + 0.6 =12.9
uncertainties
every measurement has an uncertainty
usually expressed as +/-
shows the range of values within which the true values lie
5.6cm +/- 0.1cm means that the true value could be between 5.5cm or 5.7cm
Temperature definition
a measure of the average kinetic energy of the particles in a substance.
related to the thermal energy of a substance
Microscopic energy (molecular energy)
refers to the energy associated with the motion, arrangement and interactions of particles (atoms and molecules) that make up a substance.
The several components of microscopic energy
Kinetic energy, energy due to the motion of its particles eg in gases particles move freely and have high kinetic energy (translational, vibrational, rotational)
potential energy, energy due to the position or arrangement of particles and the forces between them. eg in a liquid molecules are close but can move past each other, storing potential energy in their interactions (due to intermolecular forces)
internal energy, the total microscopic energy of a system, includes both the kinetic and potential energy of particles
for an ideal gas, temperature
measures the average translational kinetic energy of the microscopic particles (atoms and molecules), which make up body
ideal gas and energy equation
3/2 KbT = Ek_average = [1/2 mv^2] average
m = mass
T = temperature
Kb = Boltzmann constant
v = velocity
Ek = kinetic energy (energy of a moving body)
Heat
the transfer of energy from a hotter body to a colder body in thermal contact until they are in thermal equilibrium
Thermal equilibrium
two bodies that are at the same temperature
systems are said to be in equilibrium if they are able to transfer heat between each other but do not do so
Thermometric property
-A property of a body which changes with temperature
-required to measure temperature
Celsius scale
Anders celsius (1701-1744)
-put mercury in a vial
-divided the distance between 2 points into 100 equal points
-labelled each point as 1 degree each
Calibration
a comparison between measurements, one of known magnitude or correctness made with the device to be calibrated
Fahrenheit scale
Daniel Gabriel Fahrenheit (1724)
used 3 points
ice + water + aluminium chloride = 0 degrees
ice + water = 32 degrees
body temp = 96 degrees
temperature in Fahrenheit from Celsius graph
Tf = 1.8Tc + 32
T, V, P
Temperature is directly proportional to pressure if volume is constant. T goes up if P goes up if V is constant (P on y axis, T on x axis)
Volume is inversely proportional to pressure if temperature is constant. V goes down if P goes up (1/P on y axis, V on x axis)
ideal gas law, P = constant T/V (T/V on y axis, P on x axis)
Ideal gas law
PV = nRT
PV/T = constant
P1V1/T1 = P2V2/T2
Kelvin scale
Tk = Tc + 273
Pressure
P = F/A
P = pressure
F = force
A = Area
Boyle’s law
The pressure of a gas is inversely proportional to its volume at constant temperature and fixed quantity if a gas
P1V1 = P2V2
PV = constant
P = 1/V
Charles law
The volume of a gas is directly proportional to its absolute temperature when the pressure and its number of moles remain constant
V1/T1 = V2/T2
V/T = constant
V directly proportional to T
Universal gas constant
Slope = R = PV/nT
Phases of materials
Solids (Closely packed, strongly bounded to neighbours, held rigidly in a fixed position)
liquids (Still closely packed, Bonding is still quite strong, not held rigidly in a fixed position and bonds can break and reform)
Gases (Widely spaced, only interact significantly on closest approach or collision)
Specific heat capacity
The amount of energy required to change one unit of a substance by one degree
Q = mc(delta)T
Latent heat
The amount of heat energy required to change the phase f a substance without changing its temperature
Q = ml
Calorimetry
measuring the amount of heat energy transferred during a physical or chemical process. used to study the heat changes that occur during reactions, phase changes and temperature changes in substances.
Method of mixtures
-based on the law of conservation of energy
-when two substances of different temperatures are mixed together, the heat lost by the hot body is equal to the heat gained by the cold body
-heat exchange occurs until the mixtures obtain equilibrium
Conduction
The process by which heat or electricity is transferred through a substance or between substances in direct contact
Q/T = KA(delta)T/L
Q = energy
T = Temp
K = thermal conductivity of material
A = cross-sectional area through which heat is transferred
L = thickness of material
Convection
heat transfer through the movement of a liquid
radiation
the transfer of energy through electromagnetic waves
