Eng Sci Y8 Q3+Q4
Q4
Space
Q3 Biology
evolution
DENSE VERSION
Carbon cycle
components & processes
Plants
photosynthesis: the plant transfers atmospheric CO2 and water to oxygen and glucose (requires chlorophyll)
Animals
respiration: the animal obtains energy through energy, while producing atmospheric CO2 (requires mitochondria)
feeds the animal
After death:
Decomposers
decomposes/break down the dead organisms and convert them into CO2
decomposition/decay: break down from big molecules to small molecules and recycled into simpler matter like CO2
fossilization: when the dead organism is protected and under great pressure for thousands of years, it turns into a fossil
combustion
equations:
Photosynthesis: carbon dioxide+water => oxygen + glucose
Respiration: oxygen+glucose => carbon dioxide + water+energy
Combustion: oxygen + fuel => carbon dioxide + water + product
releases CO2
must involve: heat, oxygen, and fuel
Definition: the movement of carbon between different carbon stores (objects that can obtain and release CO2)
respiration: the plant obtains energy through oxygen, while producing atmospheric CO2 (requires mitochondria)
Electricity
Energy
variation: different features within or between species
discontinuous: completely inherited (such as blood type)
Continuous: takes place because of the interaction between genetics and the environment (such as height)
Natural selections (invented by Darwin)
Current: rate at which electrons flow past a certain point in a circuit
Voltage: pressure from an electrical power source that pushes charged particles in a circuit (or the potential difference between two points)
Resistance: hindrance to the flow of electrons through an electrical circuit
measured in amps using an ammeter, unit: A
measured in volts using a voltmeter, unit: V
Principles Assume all statements are under a condition of no resistance
In parallel circuit, the current is shared while the voltage is the same
In series circuit, the current is same while the voltage is shared
shared: sum of the (unit) of branch circuits = (unit) of the main circuit
same: the (unit) is equal in every part of the circuit
ammeter placed in series behind the object you measure
voltmeter placed in parallel behind the object you measure
Resistance = Voltage/ Current OR R=V/I
measured in ohms
resistance determines the voltage
Power
Power=Energy/Time
measured in watts, unit: W
one watt= one joule per second
energy transfer
measured in joules, unit: J
concepts
heat: thermal energy
temperature: the measure of heat (unit: Fº or Cº)
Conduction
Convection
Radiation
dissipation: thermal energy transfer from high temperature region to low temperature region (it is a natural tendency)
thermal equilibrium: eventual state of energy transfer in which objects that are in thermal contact reached a balanced temperature everywhere
How? in electromagnetic waves without the need of medium. It can transfer in solid, liquid, gas, and vacuum.
3 important features
reflected (white surface especially)
Determined by: density, chemical structure, states, heat capacity, ,surface area, and etc.
transmitted/emitted
absorbed (black surface especially)
It can only transfer in heated liquid or solid
It can transfer in solid (liquid and gas are poor conductors)
How? travel from particle to particle in its vibration distance
Electromagnetic Spectrum
(slowest, not harmful) radio wave < Microwave < Infrared < visible light < ultraviolet < X-rays < Gamma (fastest, harmful)
How? the particle with greater thermal energy replaces a particle with less thermal energy
Conservation of energy
Sound Waves
How sound is heard: Vibration --> Produce waves --> Hit air molecules through vibration--> Arrive at ear & vibrate & goes deeper until cochlea--> Auditory Nerve send electrical signals to brain to process
Vocab of waves
Crest: highest point
Trough: lowest point
Wavelength: distance between corresponding points
Amplitude: maximum distance moved by a point (determines loudness of sound wave)
Frequency: rate of vibration (determines pitch of sound wave)
Ultrasonic Sounds: sound with frequency higher than audible sounds
Decibel: unit used to measure the intensity of a sound wave
Why? When particles get heated, they expand, got less dense, and rise, forming a convection current in the liquid or gas. The circulation helps to distribute the hot particles more evenly. Increasing the temperature
Cooling by evaporation explained
•Average speed of the particles depends on the temperature of the liquid. (Higher Temp Higher Speed)
• The particles are colliding with each other, and energy is transferred in those collisions.
• A few of the particles at the surface will be travelling fast enough to be able to turn into gas.
• When fast-moving particles escape, the average speed of the particles left behind is slower --> colder
More efficient than conduction, because of the movement of fluids
Slower than convection, because it transfers through direct contact between materials
Def: the rate of energy transferred in a certain period of time
Sankey diagram
LHS (energy input) can be electrical, thermal, and chemical
RHS (energy output) can be light, sound and heat
Law of energy conservation: Energy cannot be created / destroyed, it can only be transferred
wanted energy output: "useful" unwanted energy output: "wasted"
Efficiency (in percentage)= useful energy / total energy output
excretion: when organisms excrete waste materials, they release carbon compounds when broken down by decomposers
Hertz: unit of frequency
longitudinal waves goes straight in one direction
In a transverse waves the motion of the particles or elements is perpendicular to the direction in which the wave is moving.
It needs a medium, so it cannot travel in vacuum. It will travel at different speeds in solid, liquid, gas. (fastest in solid, slowest in gasses)
Expansion of the universe/Big Bang
Thermal insulator traps thermal energy while thermal conductor transfers energy easily
the universe start from a substance extremely small and hot
Afterwards, stars, planets, moon, and stars were formed. The universe will be expanding forever, despite it decelerating.
The universe exponentially expanded and cooled
energy changed into particles, making atoms such as hydrogen and helium
life cycle of stars
when the hydrogen fuel of the star uses up, they turn into a red giant
the center of the red giant will shrink, becoming a white dwarf
the white dwarf cools and becomes a black dwarf
the planets gravitational strength depend on its mass (greater mass=greater gravitational force)
asteroids can form craters when it crashes toward earth
causes mass-extinction (the dust caused by impact blocks radiation, causing earth's climate to drop)
forms the moon (lighter rock of the asteroid thrown out of orbit and forms the moon)
the crater depends on the asteroid's mass, size, and direction
adaptations: changes that living organism make to survive and adapt the environment to pass on their DNA
Def: nature select the genetic compositions / survival of the fittest
populations that don't survive successfully in their environment...
extinct: dying of a species
endangered: vulnerable, threatened, low population