YEAR 8 Yearly Examination Flashcards
How do you calculate a percentage?
x/y, x 100
How do you calculate kinetic energy?
K=1/2 x mass x velocity2
Measured in Joules (J)
How do you calculate potential energy?
GPE= mass x gravitational pull x height
Measured in Joules (J)
Formula for Force, Mass and Acceleration
F M A Force = mass x acceleration Mass = force/acceleration Acceleration = force/mass
How do you calculate energy efficiency?
efficiency(%) =
useful energy output (J)/total energy output(J) x 100%
Define static electricity
- A stationary electric charge produced when a charge builds up on an object.
- The build up of electrons on an object. When one insulating material is rubbed with another insulating material it can become charged. They become charged because they either gain or lose electrons (usually through friction)
What is meant by charge? How is it produced?
There are 2 kinds of charge - positive and negative. When an object is rubbed, electrons are moved around. Electrons have a negative charge. Positive charge is due to a lack of electrons. Negative charge is due to a excess of electrons.
When is static electricity dangerous?
- when it occurs in areas where explosions are possible (ie. around flammable materials)
- when large quantities of charge could flow through a person to reach the earth
- E.g. Pumping petrol, Hindenburg airship
When is static electricity a nuisance?
- when it causes dirt and dust to become attracted to an insulator (e.g. television and computer screens)
- when it cause clothing to cling
Define the term gravity
Gravity is a non-contact force that attracts objects to each other.
Why does gravity pull objects towards Earth?
All objects have their own mass and therefore their own gravity. The greater the mass, the stronger the acceleration due to gravity. The gravitational pull towards Earth is due to the fact that the Earth has a large mass.
Common uses of magnets
- microphones
- bank cards
- headphones and speakers
- alarm bells
- safes
- door locks
- scrap yards
- maglev trains
How the poles of magnets interreact
When unlike poles are brought close together, they attract each other.
When like poles are brought close together, the repel each other.
Identify that the Earth rotates
The Earth rotates on its axis. This is the reason why we have day and night and the Sun appears to rise and set. The Earth’s axis is an imaginary line from the North and South poles. The axis is not directly straight up and down but on an angle, which Earth rotates around.
Why do we experience night and day?
The Earth’s rotation causes day and night. People receiving direct sunlight are experiencing day, whilst the other side, without direct sunlight, experiences night. The direction of rotation is from west to east, (anticlockwise), which is why people in the east of Australia start the day before those in the west.
Why do we experience seasons?
Because the axis of the Earth is tilted, we experience seasons. Earth rotates as it orbits, but the axis always points in the same direction. This means some areas of Earth are going to spend more time facing the Sun at certain times of the year.
Briefly outline the history of the telescope
The first telescopes were created in the 17th century using glass lenses. The technology has greatly improved since then. Today’s telescopes are able to see distant stars and galaxies which weren’t even imagined in the 17th century.
How does an optical telescope work?
Optical telescopes work by using light to function. They consist of lenses (refracting) or mirrors (reflecting) or both. The main lens used in called a biconvex lens. All light that travels through a biconvex lens is bent towards one point.
How have advances in technology changed and enhanced our understanding of the solar system?
Telescopes have increased our understanding by allowing us to see things that are further away than we can see with just our eyes. Over time they have improved the following ways:
- better lenses
- increased size
- increased clarity
- digital images
What is filtration and where is it used?
Filtration is a technique where a mixture is poured through a filter. Normally, the liquid passes through filter paper, leaving the solids behind. Examples include:
- vacuum cleaner
- tea bag
- air conditioner
- cigarette
What is decantation and where is it used?
Decantation allows a mixture to settle and separate by gravity. Once separated, the lighter liquid is poured off leaving the heavier liquid or solid behind. The process can be made faster by using a centrifuge. Decantation is used to separate:
- oil and water
- dirt and water
- wine
- cream and milk
- blood and plasma
What is magnetic separation?
Using the property of magnetism to physically separate a magnetic substance from a non-magnetic one in a mixture.
What is evaporation and where is it used?
Evaporation is used to separate a soluble solid from a solution. It is heated so that the water evaporates, leaving the solid behind. It can be used for:
- removing salt from saltwater
- removing water from a mineral sample
- dehydrating food
What is crystallisation?
Crystallisation is a separation technique that is used to separate a solid that has been dissolved in a liquid to form a solution.
The solution is warmed in an open container, allowing the solvent to evaporate. The saturated solution is allowed to cool so that the solid will come out of the solution and crystals will start to grow.
What is chromatography and where is it used?
Chromatography us used to separate a mixture of liquids or soluble compounds. It can be done through gas or paper chromatography. Gas chromatography is used to analyse the different liquids after they have been vaporised. Paper chromatography is done through using paper to put a sample on, and then put into a solvent which separates as the solvent travels through it. It can be used for:
- DNA fingerprinting
- Drug testing
- Purify chemicals
What is distillation and where is it used?
Distillation is a technique used to separate a liquid from a mixture. It involves three steps: evaporation, condensation and collection.
The solution is heated so that it evaporates and turns into gas, leaving everything else behind. The gas goes through a condenser, which turns it back into a liquid to be collected. This technique can be used for:
- production of important products like crude oil
- increasing alcohol content of alcoholic drinks
What is conduction and where can it be seen?
Conduction is a method of heat transfer in solids. Heat travels by conduction when fast-moving particles collide with other particles nearby, making them move faster. Heat can travel by conduction through objects or from one object to another. It can travel at different speeds, depending on the type of material and the state of matter. It travels quicker in solids because the particles are closer together. Examples:
- Heat transfer from cooktop to saucepan
- metal kitchen utensils
- ice cubes melting in hands
What is convection and where can it be seen?
Convection is a method of heat transfer in liquids and gases. The particles move faster and further apart when heated causing the substance to expand. The density of the substance is decreased, the substances cool down and the density increases. This causes them to sink back down. The circular currents are called convection currents. Examples include:
- air currents
- water currents
- magma
- chimneys
- hot air balloons
What is radiation and where can it be seen?
Radiation refers to the movement of heat energy through any space, including a vacuum. Heat which travels by radiation is called radiant heat. This heat travels very quickly. When radiant heat strikes a source it can be reflected, transmitted or absorbed. Examples include:
- heat energy reaching Earth from the Sun
heat warming the air around a fire
What is the law of conservation of energy?
- Energy cannot be created or destroyed
- Energy may change form, but the total amount remains the same
- States of energy can be converted from one form to another state of energy.
Define the term energy efficiency
Energy efficiency is a measure of how much input energy (beginning energy) is converted into useful output energy. A device is efficient if more of the input energy is being converted into the useful output energy.
Implications of energy efficiency
Energy that is ‘wasted’ like the heat energy from an electric lamp, does not disappear. instead its transformed into the surroundings and spreads out so much that it becomes very difficult to do anything useful with it. Objects that produce a lot of wasted energy are inefficient. Those that produce small amounts of wasted energy are efficient.
What are advantages in efficiency of appliances such as light globes and cooking appliances?
Light globes have been modified to be much more efficient. They now convert close to 70% of the input energy into useful light energy, rather than 30%. Cooking appliances have also become much more efficient. Stove tops used to only 40% of useful heat energy, whereas modern day stove tops can transfer 70%, and induction plates can transfer 85%.
What are the main parts of the digestive system?
Teeth, saliva, oesophagus, liver, stomach, pancreas, small intestine, large intestine, rectum
What is the role of the digestive system?
Breaks down food and allows it to be absorbed into the bloodstream.
What are the main parts of the respiratory system?
Trachea, ribs, lungs, diaphragm, alveoli, bronchiole, bronchi
What is the role of the respiratory system?
To move air in and out of the lungs, allowing oxygen to enter the bloodstream and carbon dioxide to be removed from the bloodstream.
What are the main parts of the circulatory system?
Arteries, Veins, Capillaries
What is the role of the circulatory system?
Transport:
- nutrients from digestive system to cells
- wastes away from cells
- oxygen from lungs to cells, and carbon dioxide back to lungs
- hormones to organs
How does the digestive, respiratory and circulatory systems work together?
The digestive system works with the circulatory system to transport nutrients to cells, and wastes away from cells.
The circulatory system carries oxygen from the respiratory system to other cells, allowing them to function, and also carries carbon dioxide away from cells and back to the lungs.
The digestive and respiratory systems work together to power the organism. The respiratory system allows oxygen into the bloodstream allowing cells to function, which allows the digestive system to make nutrients for the body.
What is the process of photosynthesis?
- takes place in the green parts of plants like the leaves or stem - these areas are green because they contain a chemical called chlorophyll that is produced by an organelle within the plant cell called a chloroplast.
- Requires carbon dioxide (from the air), water (from the soil) and light (from the sun).
- Makes a nutrient called glucose, which is a type of simple sugar.
Photosynthesis word equation
CARBON DIOXIDE + WATER (sunlight and chlorophyll) to OXYGEN + GLUCOSE
Photosynthesis chemical equation
6CO2 + 6H2O to C6H12O6 + 6O2
What is the process of cellular respiration?
- produces energy and this energy is known as ATP (adenosine triphosphate)
- requires glucose (from food sources) and oxygen (from the air)
- occurs in the mitochondria of cells.
Respiration word equation
OXYGEN + GLUCOSE to WATER + CARBON DIOXIDE + ATP (adenosine triphosphate)
Respiration chemical equation
C6H12O6 + 6O2 to 6CO2 + 6H2O + ATP
What is the difference between renewable and non-renewable energy? Provide examples.
Renewable energy will not run out, and will replenish itself over time. Non-renewable energy are likely to run out and will not replenish themselves over time, or will take a very long time to do so. Renewable energy: - solar energy - wind energy - hydro energy Non-renewable energy: - coal - natural gas - nuclear energy
Types of mines
- open cut
- strip
- quarry
- alluvial
- underground
What factors need to be taken into consideration before mining can commence?
- amount of resource available
- type of mining necessary
- location of mine
- cost of processing the ore
- cost of environmental rehabilitation
- world-wide demand for material
Impacts of different types of mines
Open-cut: - loss of environment and habitats - noise - pollution of water - land degradation Underground: - land subsidence - release toxic compounds into air and water
What is the tilt of the Earth’s axis?
23.5 degrees
How can Earth’s orbit around the Sun be described as?
Elliptical
What is the average distance from the Earth to the Sun?
150 million kilometres
How long does it take the Earth to orbit the Sun? What is it called?
365.25 days, it is called a revolution.
Why does the Earth stay in orbit around the sun?
Because of the gravitational attraction
