Light
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Light travels in straight line
Shadows are formed when light is blocked
Understand the factors that form bigger and small shadows
o Bigger shadows mean that more light is blocked (object closer to
light source or screen further away from object)
o Smaller shadows mean that less light is blocked (object further
away from the light source or screen nearer to the object)
Position of the light source affects the size and length of shadows (Length
of shadows is the shortest when the light source is directly above the
object. Length of shadows increase when the light source shines from the
sides of the object
Transparent objects do not form shadows as they do not block light; light
can pass through
Translucent objects form faint shadows as they block some light
Opaque objects block al the light and form dark shadows
Heat
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Heat flows from hot to cold region until both regions reach the same
temperature
Good conductors of heat allows heat to flow through it more easily/faster
while poor conductors of eat allow heat to flow through it less easily/slower
Temperature is a measurement of how hot or cold an object is
Heat is a form of energy
Heat is affected by 1) volume of object 2) Temperature of object
When heat is gained by matter, expansion takes place ( increase in size or
increase in volume BUT mass REMAINED the same)
When heat is lost by matter, contraction takes place (decrease in size or
decrease in volume BUT mass remained the same)
1)
2)
3)
When heat is gained:
Temperature of substance increases
Expansion takes place
Change of state takes place
1)
2)
3)
When heat is lost:
Temperature of substance decreases
Contraction takes place
Change of state takes place
Water and changes in state
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Water exists in 3 states and heat gain and heat loss caused water to
change state from one to another
Water cycle is a continuous movement of water which ensures the
continual supply of freshwater
Evaporation and condensation drive evaporation
Boiling point of water is at 100, melting and freezing points of water is at o.
(fixed temperatures)
Factors that affect the rate of evaporation :
1) Temperature of surrounding/ water
2) Exposed surface area
3) Presence of wind
Condensation requires 1) temperature difference 2) presence of a cooler
surface
Generally, the greater the temperature difference, the greater the rate of
condensation
Electrical system
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In order for current to flow, you need a closed circuit (no gaps)
Current can flow in a closed circuit where there is no gap; current cannot
flow through an open circuit when there is a gap
When more batteries are added in series, there is more current and the
bulb becomes brighter.
When more bulbs are connected in series, there is less current and the
brightness of bulb decreases.
When more bulbs are connected in parallel, there is more current and the
brightness of the bulb increases.
Electrical conductors (usually metals) close the circuit and electrical
insulators(usually other materials beside metals) open the circuit
Plant transport system (circulatory system of plant)
- Found in all parts of a plant
- 2 tubes to transport different substances
1) Food-carrying tubes (transports food made in the leaves to other parts of
the plant; food is able to move upwards to the flowers and fruits or
downwards towards the roots)
2) Water-carrying tubes (transport water and mineral salts from the roots
upwards to other parts of the plant) Recall: roots are the only parts that
can take in water for the plant
- Many food and water carrying tubes in the plant
Circulatory system
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Includes the heart, blood and blood vessels
Circulatory system is the transport system in humans
Blood in blood vessels transports useful substances such as oxygen and
digested food to different parts of the body and brings waste substances
to different organs for removal
Heart is a muscular pump that pumps blood around the body
All living things need energy for life processes
Respiration is the process where living things get their energy and it takes
place in all living things all the time
Digested food/ food + oxygen  energy + carbon dioxide + water
When we exercise, our body requires more energy. The breathing rate will
increase to bring in more oxygen and the heart rate will increase to
transport more oxygen and digested food to all parts of the body (muscles)
to release energy. Water and carbon dioxide are transported to different
organs for removal.
Recall: plants are living things hence they also respire.
Respiratory system
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includes the nose, windpipe and the lungs.
The breathing rate (number of breaths per minute is determined by
activities; more vigorous activities  higher breathing rate)
- At the lungs, gaseous exchange take place and oxygen is taken in while
carbon dioxide is released.
- Gaseous exchange also take place in fishes (gills) and in plants (stomata);
stomata has mainly 2 functions
1) Allows gaseous exchange to take place between the leaf and the
surroundings
2) Allows water vapour to be released to the surroundings
Cell system
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Revise parts and functions of cell parts
Understand the difference between animal and plants is that plant cells
has 1) cell wall 2) chloroplasts (found in parts that can make food)
Reproduction in humans
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Reproduction ensures the continuity of living things
Animal lay many eggs to increase the chances of survival. Some eggs
may get eaten by predators but there may be more eggs able to survive
and hatch
Heredity is the passing down of characteristics or traits from parents to
young. Most traits are passed down but there are unique traits that allow
identification and are not passed down. Traits are passed down as genetic
materials in the NUCLEUS.
Revise the PARTS and FUNCTIONS of male (Testis and penis) and
female reproductive systems (ovary, womb and vagina)
Fertilisation is the process where the male reproductive cell and the
female reproductive cell fuse.
Reproduction in plants (in no order as it is a cycle)
1) Revise the parts and functions of a flower; Recall that flowers attract
pollinators
2) Germination (W.O.W) (Process where seeds/fruits are dispersed from the
parent plants to minimise overcrowding and reduce the competition for
Space, Sunlight, Mineral salts and Water)
During germination, mass of seed leaves decrease as the food stored in
the seed leaves is used for growth
3) Pollination (Process where pollen grains from the anthers are transferred
to the stigma)
4) Fertilisation
5) Seed/Fruit dispersal (the scattering of seeds/ fruits away from the parent
plant)
- For fruits to be formed, pollination AND fertilisation MUST both take place
- Seed dispersal methods: Wind, water, explosive action ant animals (stiff
hooks to attach or juicy flesh to attract)
- Light is NOT needed for germination to take place, suitable temperature or
warmth will do
Photosynthesis
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Photosynthesis is the process where water and carbon dioxide are taken
in by the plant, and using sunlight trapped by chlorophyll to produce sugar
and oxygen
Carbon dioxide + water food + oxygen (in the presence of sunlight and
chlorophyll)
Water enters the roots and up the water-carrying tubes while carbon
dioxide enters the stomata
Factors that affect the rate of photosynthesis 1) Amount of light/ distance
between the light source and the plant 2) Amount of carbon dioxide 3)
presence of water
To find out the rate of photosynthesis, we can use the starch test or to
count the number /amount of oxygen
Plants are producers and the only organisms able to convert light energy
to chemical potential energy
Energy conversion
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Energy cannot be created or destroyed and can be converted from one
form to another
Types of energy : HKPSLE
Potential energy is stored energy and there are three types of stored
energy: Chemical, gravitational and elastic
Heat energy is present whenever there is movement due to friction.
Forces
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Forces is a pull or a push
5 Effects of forces:
Start a stationary object
Increase or decrease speed of an object
Change direction o an object
Change the shape of an object
Stop a moving object
There are four types of forces:
Gravitational force
o Pulling force exerted by the Earth on ALL objects towards the
center of the Earth
o Constant on Earth
Elastic spring force
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o Present in stretched and compressed springs (if not spring, use
elastic force instead)
o Elastic spring force returns stretched or compressed springs into
the original length
Magnetic force
o 2 types of magnetic force; magnetic force of attraction (between
unlike poles) and magnetic force of repulsion (between like poles)
o Recall repulsion (Like poles of 2 magnets facing each other hence
they repel)
Frictional force
o Exists between 2 surfaces in contact
o Opposes motion
o Affected mainly by the surface of the object (there is more friction
on rougher surfaces than on smoother surfaces)
o Affected by mass of object (heavier object has more frictional force
hence needs more frictional force to stop)
o Generally not affected by surface area
o Frictional force can be reduced using lubricants, water, powder,
using ball bearings and wheels)
Interactions within the community
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Factors within the environment include temperature, light, amount of
oxygen/air, amount of water and other presence of other living things
2 types of adaptations (characteristics which help the organism survive
better in the environment):
Structural (Physical characteristics)
Behavioural (Actions by the organisms)
All organisms (including plants) have both structural and behavioural
adaptations to enhance their survival
A habitat is where an organism lives
Organism  population  community
Organism is a living thing
Population is made up of many organisms of the same type living together
and reproducing in the same habitat
Recall: young and adult of organisms belong to the same population.
Only eggs are excluded from population as we are unsure if eggs can
hatch
Community is made up of many populations living together and depending
on each other in a habitat
Each food chain starts with a producer as they are the only organisms that
can make their own food
A food chain shows the feeding relationships between different organisms
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Producers (make their own food) consumers (feed on other organisms)
Consumers include 1) plant eaters 2) animal eaters 3) plant and animal
eaters and 4) decomposers
Plant eaters ARE NOT predators as they eat only plants
Animal eaters as well as plant and animal eater can be prey or predators
in a food chain
Many food chains form a food web
A food web is made of interconnected food chains
Man’s impact on the environment
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Revise pollution (Air, water and land)
Revise deforestation (destruction of large numbers of tress by burning or
cutting down trees)
Effects of deforestation:
o Loss of habitats
o Soil erosion (less roots to hold onto soil, fertile soil is washed into
water bodies)
o More carbon dioxide in the air (less trees to take in carbon dioxide
during photosynthesis)
o Less rain (less water vapour given off by the plants less clouds
less rain)
o Carbon dioxide produced during burning/ carbon dioxide not taken
in during photosynthesis is a greenhouse gas and will heat to be
trapped within the Earth; leads to global warming
Effects of global warming (increase in temperature of the Earth):
o Loss of habitats
o Increase in sea levels (ice are melting at the poles)
o Climate change (more floods and droughts)