science Flashcards
democritus was a greek philosipher who propsed
matter could not be divided into smaller pieces forever;matter was made from small, hard particles called atoms
john dalton confirmed atoms
are tiny solid balls and created the first atomic theory`
jj thompson came up with the plum pudding model and discovered electrons with
cathode rays - he showed the atom was made of smaller things
ernest rutherford discovered protons and the nucleus using his
gold leaf experiment
in the gold foil experiment it was concluded there was a dense positive centre because
the alpha particles did different things - scattered, scattered a lot, and went through the foil
niels bohr created the bohr model from discovering that
every atom has a specific number of electron shells (and that there were shells )
erwin schrodinger and werner heisenburg led to the idea of
electron clouds
jameschadwick created the modern model which included
protons, electrons AND neutrons
a physical change is one where
no new substances are formed. It is usually reversible
physical change examples could be
ice melting, melting chocolate, breaking a glass (solid, liquid, gas)
a chemical change is a change in which
a new substance forms. It is irreversible.
chemical change examples could be
cooking food, fireworks, leaves changing color
what are some signs of a chemical change?
odour is given off
hear a bang/fizzing - effenresence; bubbles in a liquid, fizz
increase /decrease in temp
see fizzing/ change in color
what is a precipitate?
a solid substance that forms at the bottom of a solution
chemical changes happen when
chemical reactions occur
chemical change involve
the formation of new chemical elements/compounds
physical changes don’t lead to new chemical substances. instead,
a substance simply changes physical state (solid-liquid)
reactants=products
reversible
reactants-products
irreversible
during irreversible chemical changes, the number of atoms stays the same either side whilst the products and reactants
simply rearrange
exothermic
energy out to surroundings (temp up)
endothermic
energy in from surroundings (temp down)
potassium + nitrogen + oxygen -
potassium nitrate!
in a word equation, if there is 3 reactants - including oxygen -
ate e.g. nitrate
in a word equation if there is 2 reactants - ending witth non-metal -
ide e.g. chloride
calcium + fluorine =
calcium fluoride
H + O2 - H2O
4H + O2 - 2H2O
(s) = solid (l) =liquid (g) = gas
(aq) = aqueous - dissolved in water
balancing tip
LHS E RHS
1 C 1
PHOTOSYNTHEISIS -
converts light into chemical energy
cellular respiration -
breakdown of glucose to release energy
rusting is iron reacting with
oxygen and water
combustion is when fuel reacts with
oxygen to release energy
the law of conservation of mass
total mass of reactants
= ————————————-
total mass of products
when one of the products is a gas,
the mass does not/may not appear conserved - it may appear to be less than that of the reactants
when balancing chemical equations
-only change the molecule number
- whole numbers only
- tackle more unusual ones first
Aerobic respiration
occurs with oxygen and releases more energy but more slowly.
Anaerobic respiration
occurs without oxygen and releases less energy but more quickly.
example of endothermic reaction
photosynthesis
e.g. of exothermic reaction
cellular respiration
in photosynthesis (endothermic) light energy is converted into chemical energy which is stored in the bonds of
C6H1206 aka glucose
carbon dioxide + water -
glucose + oxygen
oxygen + glucose -
carbon dioxide + water
products of photosynthesis become the reactants for
cellular respiration
rust = iron oxide
-compound
-powdery
-flakes
formation of rust when a metal(iron) reacts
with oxygen in the presence of water
steel contains iron and is therefore
prone to rusting
ways to prevent rust
painting, oiling, galvanising, covering in plastic
what is combustion?
burning - fuel combining chemically with o2 then releasing energy
complete combustion needs o2 -
carbond ioxide vs carbon
is combustion endo or exo thermic
exothermic becasue of the heat givem out to surroundings
what is the combustion word equation
fuel + oxygen - carbon dioxide + water (+energy)
to test for the presence of hydrogen you do the
squeaky pop test
energy def
energy is the ability to do work
energy measuring unit?
joules ( J )
work done -
energy transferred
energy cannot be created or
destroyed
energy = E in
equations
P =
e/t
what is Ek?
kinetic energy
what are the two main types of energy?
kinetic and potential
what is kinetic energy?
motion
what is potential energy
( stored due to the positioning
examples of kinetic energy
light energy, sound energy, a moving car or rolling ball
examples of potential energy
a streched rubber band, book on the shelf, GPE, nuclear energy
9 types of energy
chemical, thermal, light, sound, magnetic, gravitational, elastic, electrical, nuclear
4 ways energy can be transferred
electrically
heating
mechanically
radiation
transferred means
one store to another
transformed means
the process of changing energy from one form to another, like converting electrical energy inro light energy (bulb)
what does the law of conservation of energy state?
energy cannot be created or destroyed, only transformed from one form to another/transferred
what is useful energy?
energy which is required for the object to work e.g. with a car its kinetic
what is wasted energy?
energy that has been transferred to another store and isn’t useful e.g. with a car its the thermal store
when a rollercoaster reaches the peak, what happens to the ke and gpe?
hight gpe and low ke
when a rollercoaster reaches the slope downwards, what happens to the ke and gpe?
high ke low gpe
when a rollercoaster starts climbing to the top, what happens to the ke and gpe?
low ke and high gpe
when electrical enrgy goes into a tv, what comes out?
light, sound and heat energy
when chemical potential enrgy goes into a torch, what comes out?
light energy and heat energy (wasted)
when electrical enrgy goes into a tv, what is the internal component?
electrical energy
when chemical potential enrgy goes into a torch, what is the internal component?
electrical energy
when electrical energy goes into a kettle, what comes out
thermal energy and sound energy
when cpe goes into a radio what comes out?
sound and heat energy
when cpe and kinetic energy (hands) goes into a guitar what comes out?
kinetic energy (strings), sound energy, heat
what is the energy transfer when a pen is dropped?
Ek in hand is transferred to pen which then had Ek
what is the energy transformation when a pen is dropped?
Ek of pen transforms into GPE as lifted - GPE of pen is transformed into kinetic energy when pen drops
what is the energy transfer when a guitar is strummed?
Ek in the hands to Ek in the strings
what is the difference between thermal and heat?
thermal energy is a store, heat is a transfer
GPE FORMULA
GPE = mgh
KE FORMULA
KE =1/2 mv (squared)
g - kg
divide by 1000
always do v squared first then
times it by 1/2 m
IN GPE YOU NEED KG AND M!
IN KE YOU NEED KG AND M/S
metalloids have
properties of both metals and non metals
metals are malle-
able
Malleable means you can beat it into
thin sheets ( e.g. gold)
metals are sono-
-rous
sonourous means capable
of producing a deep ringing sound
metals are lustrous. lustrous means shiny or
able to be polished
brittle means when hit, fractures without
elastic deformation (nonmetal)
conducter let
heat and electricity pass through easily - metal
Insulators donot
let heat and electricity pass through easily - non metal
copper -
cu
lead
pb
iron
fe
a pure substance consists only of one
element/compound
A mixture consists of two or more
element/compounds not chemically joined togeteher
all matter is made from
atoms
atoms are made of even simpler sub-atomic particles -
protons, neutrons and electrons
9, F, 19
9 is the atomic number, F is the symbol, 19 is the atomic mass
electrons are in
orbits/shells
atomic number is
protons or electrons
atomic mass is
protons+ neutrons
a protons charge and relative mass is
charge +1 and relative mass is 1
a neutrons charge and relative mass is
charge 0 and relative mass is 1
a electrons charge and relative mass is
charge -1 and relative mass is 0.0005
electrons maximum number of orbits is (from in - out)
2,8,8,2
atoms have a overall? charge
neutral
charged particles are
ions
+ CHARGED = p>e
cations
- CHARGED = p<e
anions
carbon dioxide and table salt are both
compounds
e.g. molecular structure
oxygen, co2,mwater, glucose
e.g. lattice structure
sodium chloride, diamond and graphite, silicon dioxide
matter occupies
space and has mass
there are 118
elements
elements are made of only
1 atom type
diatomic elements consist of
2 atoms e.g. o2
compounds are
2 or more different elements or types of atoms chemically joined togetehr
atoms are the smallest particles
substances can be broken down into
element exampless
o2, magnesium, calcium
compound examples
water, copper sulphate,
mixture examples
air, salt water, milk
single atoms are called
monatomic
clusters of molecules are
diatomic
lattices are
large grid like structures
molecule means
a group of atoms chemically joined together
elements and compound can have
entirely different properties
non metal elements tend to form
molecules
metal elements tend to form
lattic structures
most non metallic structures are made of
molecules
crystal lattices are
grid like structures that repeat the s arrangement of atoms over and over
diamond and graphite an dgraphene
are carbon allotropes
allotropes are
different structual forms of teh same element
describe a diamond
lots of bonds, no free electrons, high melting oint, hard and dense, doesn;t conduct electricity
describe graphite
weakly bonded delocalised electrons, high melting point, conducts electricity, soft and slippery
graphene is a
single layer of graphite
thermal energy is a
energy store
thermal energy is a measure of all
the total kinetic energy of all particles in a substance
the greater the volume the ? thermal energy
more ( more particles)
thermal energy always moves from
warmer - colder objects by heat transfer
thermal energy is measured in
joules (J)
Temperature is a measure of how
hot/cold a substance is
Heat is a type of energy
transfer
Heat is the amount of energy
that is transferred from one object to another due to temp difference
Heat travels from hot-
cold
thermal conductors allow heat
to transfer through easily
thermal insulators ? heat to transfer through
don’t allow
The rate at which objects transfer enrgy ( or lose heat ) depends on:
- Sa - volume ratio
- The objects material
( conductor/insulator ) - The temp difference between the object and it’s surroundings
high SA:V ratio means
high rate of energy transfer
conducting material means
high rate of energy transfer
high temp differnce means
high rate of energy transfer
Conduction state
solids
Convection state
fluids ( liquids + gases ) - particles
radiation
vacuum
conduction is the transfer of heat energy by
direct contact and the passing of vibration from a hot - cool object
convection is the transfer of heat energy by
liquid/fluid motion from a hot ocject to a cool one
an example of convection is
boiling water
Radiation is the transfer of heat energy by
waves from a hot - cool object
radiation has no involvement of particles, only waves - true or false
true
name some good conducters
copper, brass, silver, aluminum
name some good insulators
wood, plstic, paper, wool, foam, glass, air
In conduction, an object is heated - causing the atoms to
vibrate.
These Vibrations make the atoms next to them vibrate, and so on. This is how the heat energy
travels along a solid e.g. plastic and wood
Metals (then collide with neighbouring atoms ) contain free elctrons that aren’t attcahed to the atom and are free to move around. The heat can be transferred faster than in a n insulating material bc
electrons have a smaller mass than atoms
high ke by heating means atoms collide with
neighbouring particles and energy is transferred.
When part of a liquid or a gas is heated, the particles gain
kinetic energy and move apart from each other
When heated, fluids become less dense and rise. Once that happens they cool down bc they are
further from the heat
The particles lose energy when cooling down and become more dense and closer together - making it
sink. This is how a convecton current happens
Heat Radiation can also be called
infrared radiation
Radiation travels fastest in a
vacuum ( at the speed of light )
Radiation can travel through
solids, lliquids and gases
poor absorbers are poor emitters
of radiation and emit much slower
why do polar bears cover their nose?
to minimize heat loss
the bigger the SA the more infrared waves can be emitted -
so the quicker the heat transfer
all things absorb and emit
infrared raduation
the hotter something is the ? infrared radiation it emits
more
Some things glow when they are hot- this means they are giving out
visible radiation as well as infrared radiation so we can see them.
Matte black surfaces aare very good
absorbers and emitters
Matte Black surfaces are very bad
reflectors
Shiny silvery white surfaces are very bad
absorbers and emitters
Shiny silvery white surfaces are very good
reflectors
What is Double glazing?
2 pieces of glass are used in a window with a gap in between filled with air/vacuum.
how does double glazing minimize heat loss in our homes?
It reduces heat loss through conduction a s air is and insulator A vacuum prevets loss by conduction and convection
What is a wall cavity insulation?
if the cavity ( gap ) in the wall is filled with only air, the air can move around and teransfer heat from the inner wall
how to minimize heat loss in radiators
aluminmunm foil between the radiator and the wall reflects the heat radiation away from the wall as silver is a good reflector
GPE =
Mgh
gpe is measured in
joules
in GPE - m ( mass ) is measured in
kg
in GPE - g ( gravity on earth ) is measured in
n/kg
in GPE - h ( height ) is measured in
m ( meters )
g on earth aka n/kg is
9.81 N/kg
what is one way a thermos works?
The plastic cap stops cooling by evaporation and convection and conduction
CO2 test is
cloudy lime water
Neutral oject
balanced number of + AND - CHARGE
Positive Object
more + than - charge
Negative Object
more - than + charge
Charged Object
unbalanced number of + and - charge
Atoms are neutral bc
Protons = Electrons
charged particles are called
ions
positively charged particle ( p>e )
cations
negatively charged particle ( p<e )
anions
two oppositely charged objects means
attraction
two similarly charged objects means
repulsion
The moving of charges through electricity is a form of energy transfer - it can be referred to as
electrical energy which is a form of Ek ( when applied to moving charges )
3 elements of an electric circuit
1) an energy source e.g. battery
2) a conducting path e.g. wire
3) an energy user e.g. lightbulb
electrical circuit is a
closed loop
Current ( I ) is a measure of
the flow of electrons ( moving ) around the circuit
Potential Difference/Voltage ( V ) is the force
driving the flow of elecetrons provided by cell battery
an example of something for electrons to flow through
wire
current is measured in
amps using an ameter
1Amp =
1000 ma
what is the difference between a cell and a battery
A cell is a single device that converts chemical energy into electrical energy, while a battery is a collection of cells that provide a steady source of electrical energy.
A battery provides a higher voltage and more energy than a single cell.
the force that causes opposite charges to attract is called
electrostatic force
Electrons leave the - terminal of a power supply bc
they are repelled by the - terminal ( like charges repel )
Electrons move from the negative termina to the
positive bc opposite charges attract
We show the current moving from the positive to negative terminal
even though its wrong
a circuit that only has 1 path for the current to flow through is called a
series circuit
a circuit that has more than 1 patyh for the current to flow through is called a
parallel circuit
what are 2 adavantages of household wiring being on a parallel circuit?
1) some appliances can be on while others are off ( acheived by inserting switches )
2) if one appliance fails, the others will still work
Voltage is the
amount of energy used up by a charge ads it moves through a load/ressistor
Potential energy transformed as charge moves through a
component
Resistance ( R ) is measured in
ohms Ω
Resistance opposes the flow of charge in an
electric circuit
a resistor is a device
deliberately placed in a circuit to control the size of the current
high # of components means
high resistance
high temp of wire means
high resistance ( more cahllenging for electrons to get through )
Ammeters must be connected to
series circuit
Voltmeters must be connected to
parllel circuit
when in a series circuit, current
stays the same
when in a series circuit, voltage
splits
when in a parallel circuit, voltage
stays the same
when in a series circuit, current
splits
which time of diagram helps look at efficiency?
sankey diagram ( arrow )
Efficiency (%) =
useful energy output/total energy input x 100
P = e/t
power = energy/time
power is measured in
joules/second
joules per second is also known as
watts ( w )
1000w =
1KW
Kwh ( kilowatthour) is a
unit of energy
Why is efficiency important for personal cost?
pay less for the same output
Why is efficiency important for the environment?
Where does energy come from? - non renewable resources such as fossil fuels like coal, oil which contributes to global warming. We want renewable resources liek solar or tidal power
Cost =
power x time x tariff
Power = kw
time = hours
Tariff = 27.56
we want
50000 hours
