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Science - Coggle Diagram
Science
Application of Forces and Transfer of Energy
What is a Force?
A push or a pull
Effects of forces
A force can change the size and shape of the object
A force can move a stationary object
A force can change the direction of moving object
A force can change the speed of an object (speed up or slow down)
A force can stop a moving object
A force can bring about a turning effect in objects
Types of Forces
Contact Forces
Frictional Force
Friction is the force that resists motion
How does it work?
Two rough surfaces in contact with each other have tiny irregularities and projections that interlock, hence resisting motion
Effects of Frictional Force
Positive Effects
Friction enables one to walk without slipping
Friction enables one to hold a pen and write on a surface
Friction enables vechicles to slow down and come to a stop
Friction enables a match to be struck
Negative Effects
Friction produces heat - this reduces efficiency as some of the input energy is wasted as thermal energy instead of useful output energy
Friction can cause machines to wear down and become unusable over time
How can you reduce friction?
Streamlined in Shape
Reduces air and water resistance
A streamlined shape has a narrow head and tail, with a wide body
Levitation
Reduces friction by reducing contact surface area
Examples
A hovercraft 'floats' or hovers above water on a cushion of air to reduce friction between the base of the hovercraft and water.
A maglev (magnetic train) is levitated (lifted) above its track by the magnetic force of repulsion between the train and the tracks
Lubricants
Grease
Oil
Ball Bearings
Non-contact forces
Magnetic Force
The force of attraction or repulsion produced by magnets
Uses of Magnetic Force
Lift heavy objects made of iron and steel in scrapyards
Separate magnetic and non-magnetic materials in recycling plants
Gravitational Force
The force of attraction between two bodies, which acts at a distance
It causes objects to fall
Example: The gravity of the Sun causes planets to orbit around it
SI unit of Force is the Newton (N)
Can be measured using a spring balance
Formulas
W = mg
W = Weight (in N)
m = mass of body (in kg)
g = gravitational force (N/kg) [dependent of location]
P = F/A (Pressure is the perpendicular force acting over a unit contact area)
P = Pressure (in pascal(Pa) or N/m^2)
F = Perpendicular force (in N)
A = Total contact area (in m^2)
W = F * d (Energy is the ability to do work)
W = work done by a constant force F (in J)
F = constant force (in N)
d = distance moved by object in the direction of the force (in m)
GPE = mgh
m = mass of body (in kg)
g = gravitational field strength (10 N kg^-1 on Earth)
h = height above ground (in m)
KE = 1/2(m*v^2)
KE = kinetic energy (in J)
m = mass of body (in kg)
v = speed of body (in ms^-1)
The Principle of Conservation of Energy (COE)
1) Energy cannot be created nor destroyed
2) Energy can be converted from one form to another
Sources of Energy
Non-renewable sources of Energy
Fossil Fuels
Type of Fossil Fuels
Coal
Gasoline
Petrolium
Diesel
Energy Conversion
Chemical Potential Energy -> Heat Energy -> Kinetic Energy -> Electrical Energy
Effects
When fossil fuels are burnt, greenhouse gas is produced.
Contributes to Climate Change
Renewable sources of Energy
Solar Energy
Light Energy and sometimes Heat Energy from the Sun is converted into electrical energy by Solar Panels
Energy Conversion
Light Energy + Heat Energy (from the Sun) -> Electrical Energy
Hydroelectric Energy
Hydroelectric Power Stations store water in a reservoir behind a dam
Energy Conversions
Light energy (sun) -> Heat Energy -> Gravitational Potential Energy -> Kinetic Energy (Water) -> Kinetic Energy (Turbines) -> Electrical Energy (Generator)
Impact: Flooding might occur and affect the surrounding living things
Advantages: No pollutant
Wind Energy
Energy Conversion
Kinetic Energy (Wind) -> Kinetic Energy (Wind Turbine) -> Electrical Energy (Generator)
Advantage: No pollutant
Disadvantage: Requires large area to build
Geothermal Energy
Derived from hot rocks deep underground in Earth. By drilling deep into the Earth, water flowing through huge underground pipes is used to generate electrical energy
Impact: May extract toxic elements (e.g. hydrogen sulfide)
Energy Conversion
Heat Energy (Earth's Core) -> Kinetic Energy (Steam) -> Kinetic Energy (Turbines) -> Electrical Energy (Generator)
Biofuels
Derived From animals wastes and pant matter such as sugar cane, which are then used to produce electricity
Uses: Biodiesel fuel for motor vehicles
Impact: Produced carbon dioxide when burnt, which leads to climate change
Types of Chemical changes
Thermal decomposition
Process in which a substance is break down into two or more simpler substance by the effect of heat
Examples: Sugar -> Carbon + water vapour
Oxidation
Process in which a substance reacts with oxygen
Example: Rusting
Water + Oxygen -> rusting
Combustion
Combustion refer to the combination of a substance with oxygen in the presence of heat
Examples: In car engines, petrol burns in oxygen to produce carbon dioxide and water vapour Petrol + Oxygen -> Carbon Dioxide + Water vapour
Reactions caused by light
Light interacts with matter to cause chemical changes such as in Photosynthesis and X-ray film
Examples in Photosynthesis:
Plants use sunlight to make food
Carbon Dioxide + Water -> Glucose + Oxygen
Reactions caused by electric current
Passing an electric current through a substance also produces some chemical changes like electolysis and electroplating.
Examples in Electrloysis:
Electrolysis is the chemical decomposition of substances with the passage of an electric current. Water -> Hydrogen + oxygen
Neutralisation
The process where an Acid reacts with an alkali to form a salt and water mixture
Examples:
Magnesium hydroxide(Alkali) + Nitric acid(Acid) -> Magnesium Nitrate + water
Chapter 10: Transfer of heat energy and its effects
The 3 Types of Transfer of Heat Energy
Conduction
The process by which thermal energy is transmitted from a region of higher temperature to a region of lower temperature from one particle to another without any net flow in the medium
Only means of transfer of thermal energy in solid mediums
How does conduction work?
When one end of a material is heated, particles there gain kinetic energy and vibrate faster and more vigorously
These particles collide more frequently with less energetic neighbouring particles causing them to gain kinetic energy
These neighbouring particles vibrate faster and more vigorously and the energy is passed along to the rest of the particles in the bar
Convection
Convection is the process by which thermal energy is transmitted from one region to another in a fluid by the circulation of currents that direct the flow of the particles of the fluid.
How does convection work?
When water at the bottom of the flask is heated, it expands. The expanded water is less dense than the surrounding water and rises. Since the upper region is cooler, it is denser and therefore sinks. The difference in the densities of water in the different regions sets up a convection current.
Examples of Convection
Sea Breeze
In the day, land heats up faster than the sea
Air above the land is heat, expands and rises
Cool air above the sea is denser and moves in to replace the warmer air
Result in sea breeze
Land Breeze
At night, the land cools faster than the sea
Warm air above sea rises
Cooler air above land moves out to take its place
Result in land breeze
Radiation
Radiation is the transfer of thermal energy by electromagnetic (infra-red) waves from the surface of all bodies, transmitted without the aid of a medium
Radiation can take place in a vacuum, unlike conduction and convection
More about Infra-red waves
Travels at the speed of light
Travels in all directions
Factors that affect rate of emission and absorption of infra-red waves
Temperature (of obj)
Surface Area (of obj)
Colour (of obj)
Duller Colours = Higher rate
Shinier Colours = Lower rate
Texture (of obj)
Rougher = Higher rate
Smoother = Lower rate
Definitions
Temperature
The measure of how hot an object is
SI unit of temperature is Kelvin (K)
The more heat an object has, the more vigorous it's molecules vibrate
Heat
Heat is a form of energy which flows from a region of higher temperature to a region of lower temperature
What causes transfer of thermal energy?
Thermal energy is transferred only when there is a difference in temperature
Thermal energy always flows from a region of higher temperature to a region of lower temperature
There is no transfer of heat at thermal equilibrium
States of Matter
Solid
Usually solids expand when heated, and contract when cooled
Some solids expand very little such that we may not notice the expansion
Liquid
In general, most liquids expand when heated, and contract when cooled
Gas
In general, most gases expand when heated, and contract when cooled
Plasma (Optional to learn)
Bimetallic Strips
How does it work?
The brass expands more than the iron when heated. Hence, the heated strip bends with the brass on the outside of the curve.
When cooled, the brass contracts more than the iron. Hence, the strip bends with the iron on the outside of the curve.
A bimetallic strip consists of two different metals that expand at different rates when heated. They are usually brass and iron
Uses
It can be used in appliances that rely on temperature regulation
pH scale
A measure of acidity
pH indicators
Universal indicator
Changes colour depending on pH
Litmus paper
Red -> Blue if alkali
Cum is alkali
Law and order intensifies*
Blue -> Red if acid
What does it mean?
pH=7: neutral
pH<7: acid
pH>7: alkali
Cum pH=8.2, it is alkali
Word equations
Acids
Sulfuric acid
$$ H_2SO_4 $$
Hydrochloric acid
$$ HCL $$
Nitric acid
$$ HNO_3 $$
Chemical reactions involving acids
Metals
Metal + Acid -> Salt + Hydrogen
Alkalis
Alkali + Acid -> Salt + Water
Carbonate
Carbonate + Acid -> Salt + Water + Carbon dioxide
examples of word equations
Calcium Carbonate(Carbonate) + Hydrochloric Acid(Acid) -> Calcium Chloride(Salt) + Carbon Dioxide + Water
Magnesium(metal) + Nitric acid(Acid) -> Magnesium Nitrate(Salt) + Hydrogen
Sodium Hydroxide(alkali) + Sulfuric Acid(Acid) -> Sodium Sulfate(Salt) + Water
Physical and Chemical changes
Physical changes
Reversible
Properties of the product are the same as reactants
No new substance formed
Little or no heat involved
Chemical Changes
Usually irreversible
Properties of the product are different from the reactants
New substances formed
Heat or light involved
Chapter 12: Interactions Within Ecosystems
What is ecology?
Ecology is the study of interactions of organisms with each other and with the environment
Ecosystems
Meaning
An ecosystem is made up of interactions between a community and its physical environment
Types of Ecosystems
Desert Ecosystem
Examples
When it rains, the seeds in the desert quickly mature and grows. It quickly produces new seeds before there is no more water left from the rain
Due to extreme temperatures and lack of water, life is not abundant in hot deserts
Seashore Ecosystem
Marine Ecosystem
Examples
What happens to corals when temperature of the sea water rises?
Corals become bleached
Microorganisms in the corals that can photosynthesize and help corals survived died
The corals won't have much food left to live on, thus the corals will die eventually
The sea creatures that uses the corals to hide from their prey to hunt or uses the corals to hide from their predators will also decrease in population size since the corals are dead.
Tropical Rainforest Ecosystem
The rainforest has a relatively warm and humid environment
Physical factors of its environment
Air is warm and has high humidity
Rainfall is frequent and abundant
Average temperatures are high and the daily temperature range is narrow
A large amount of sunlight reaches the tree canopy, but little sunlight reaches the ground
Minerals are plentiful and mainly found near the surface of the soil
The soil is usually acidic
Examples of adaptive traits some organisms living in the rainforest
Stick insect
Structural adaptation
The colour and shape of its body match those of a leaf or twig, making it difficult to be spotted by its predators
Behavioural adaptation
It stays very still and moves slowly to avoid detection by predators such as brids
King cobra
Structural adaptations
Its venom helps in its hunt for prey
Its forked tongue gives it a keen sense of smell which helps it to find prey
It uses its inner ears to detect vibrations in order to hunt prey
Behavioural adaptations
It hunts during dawn or dusk when there is little light, to avoid being detected
It lifts its body and makes a hissing sound to warn its enemies
When provoked, it can be highly aggressive to protect itself
Velvet tamarind tree
Structural adaptations
Its buttress roots, or large, wide roots, provide support and help to take in minerals near the surface of the soil
It grows very tall to allow its leaves to trap more sunlight
Mangrove Swamp Ecosystem
The mangrove swamp is a coastal habitat
Physical factors of its environment
The habitat is immersed in seawater at high tide and becomes dry at low tide
It is exposed to freshwater when it rains
The habitat is exposed to a lot of sunlight
The seawater carries many minerals to the habitat
The seawater is slightly alkaline
Examples of adaptive traits some organisms living in the mangrove
Pistol shrimp
Structural adaptation
Its enlarged claw enables it to shoot a jet of water and create a bubble. When the bubble bursts, the high pressure and temperature generated can catch its prey off guard
Behavioural adaptation
It lives in burrows to protect itself against predators
Mangrove snail
Structural adaptations
Its thick shell provides protection
The colour of its shell matches that of its environment, making it difficult to be spotted by its predators
It produces and releases mucus, which enables it to cling tightly to trees and avoid being washed away during high tide
Behavioural adaptations
It is usually active when submerged in seawater to hide from its predators
It hides in cracks or under rocks to keep itself cool
It climbs trees to avoid its predators
Mangrove tree
Structural Adaptations
Its many strong roots help to anchor it in the mud
Its breathing roots help it to obtain oxygen
Its ability to remove salt taken in from seawater allows it to survive in its environment
Mudskipper
Structural adaptations
Large gill chambers to store water and keep gills moist when it is dry
Gills absorb oxygen in water, skin absorb oxygen when dry
Eyes at the top of head to check for danger and food
Behavioural adaptations
Digs burrows to hide for protection and to remain cool
Feed on floor available at mud surface
Environment influence the survival of organisms
Physical Factors
Air/Oxygen
Water
Temperature
Light intensity
Mineral Content
pH
Measured with pH meter connected to a datalogger
All of the above are measured b y instruments such as dataloggers and probes
Humidity
Adaptations in Organisms
Structural Adaptations
Physical characteristics of an organism that help it to survive in its habitat
Behavioural Adaptations
Refers to the different behaviours of an organisms that allow it to survive in its habitat
Only organisms that are suited to live in their specific environment survive long enough to reproduce. We say that they have adaptive traits that enable them to grow well in their environment
