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Cells & Biotech Answer Key
Cells & Biotech Practice Questions
Cells and Biotechnology
Chemistry Answer Key
Chemistry Practice Questions
Energy Answer Key
Energy Practice Questions
Framework Strand 1
Framework Strand 2
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Framework Strand 4
Framework Strand 5
Genetics and Evolution
Genetics Answer Key
Genetics Practice Questions
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Energy is the capacity to do work
The unit of energy is a calorie
A calorie is the amount of heat energy needed to raise 1 gram of water by 1 degree Celsius
A food Calorie equals 1000 calories
The rate at which electrical energy is used is measured by watts
Example: 100 watt light bulb uses twice as much energy as a 50 watt light bulb
Fuels are sources of energy
Electrical energy can be transmitted through conductors such as metal wires
It can also be produced by other sources
Other sources of energy include hydroelectric energy and nuclear energy
Hydroelectric energy is electricity produced by the power of flowing water
Water in motion has kinetic energy which can be transformed into electricity
Hydroelectric energy is clean and inexpensive
Nuclear energy is the energy storied in the nucleus of an atom
When the energy is released, it creates heat which can be used to produce electricity
Describe the effects of adding energy to matter in terms of the motion of atoms and molecules, and the resulting phase changes.
1) Kinds of Energy
Potential Energy is stored energy that an object has because of its position or its chemical composition
Example: a rock on a cliff top because of its position
Example: lump of coal because of its composition
Kinetic Energy is energy that an object has when it is moving
Example: a rock falling off the cliff
Example: heat giving off from burning a lump of coal
Potential energy may be changed to kinetic energy when motion is produced
Example: water held back from a dam has potential energy, when it is released, the potential energy is changed to kinetic energy
Bill Nye on Types of Energy:
2) Forms of Energy
Mechanical energy is the energy with which moving objects perform work
Chemical energy is energy stored in certain substances because of their chemical makeup
Magnetic energy is present in certain objects that is rich in iron
Nuclear energy is the energy stored within the nucleus of an atom
Other forms of energy include sound, heat, light, and electricity
3) Energy Transformation
Energy can be transformed from one form into another
Example: chemical energy in gasoline is changed into mechanical energy that turns the wheel of the bus.
Provides heat, light, electricity and motion
4 states of matter:
Solid: atoms are tightly packed together with a definite shape and volume.
Liquid: atoms move around more and tend to “flow”. No definite shape but has a fixed volume.
Gas: atoms are really spread out and have no definite shape or volume.
Plasma: is ionized gas which only exists in space. The atoms are positively charged and share space with free negatively charged elections. Plasma can conduct electricity and interact strongly with electric and magnetic fields.
More information on states of matter
Usually, when energy is added to a substance, the current state of matter is changed
Example: Heat added to water will make the water go from a liquid to gas
Example: Heat added to ice will make the ice go from solid to liquid
When molecules or atoms are heated, they move around more which results in phase change. Less movement equals the state of solid, more movements equals the state of gas.
Energy of fossil fuels, solar radiation, or nuclear fuels can be converted into other energy forms such as electrical, propulsive, or heating that are most useful to us
Often, machines are used to transform energy
Processes which convert heat into other forms of energy are inefficient
Explain how energy is transferred by conduction, convection and radiation.
4) Types of Heat Transformation
Convection is the transfer of heat by the actual movement of the warmed matter
Example: Heat leaves the coffee cup as the current of steam and air
Transfer of heat energy is in a gas or liquid by movement of currents
Conduction is the transfer of energy through matter from particle to particle
It is the transfer and distribution of heat energy from atom to atom within a substance
Example: a spoon in a cup of hot soup become warmer because the heat from the soup is conducted along the spoon
Conduction is most effective in solids, but can occur in liquids
Radiation is electromagnetic waves that directly transport energy through space
Sunlight is a form of radiation that is radiation through space to our planet
Radiation does no use the aid of fluids or solids
Energy travels through nothingness
Since there are no fluids in space, convection is not responsible for transferring the heat
Describe energy transformations among heat, light, electricity and motion.
Energy is transformed from heat and light through conduction, convection and radiation
Energy transformation from electricity and motion is not through conduction, convection and radiation
Potential energy may be changed to kinetic energy when motion is produced
Explain the relationship among voltage, current and resistance in a simple series circuit.
Simple Series Circuit
Consists of three basic elements: a source of electricity, usually a battery or a wall outlet, a path or conductor for the electricity to move through (wire), and an electrical resistor, such as a light bulb, that requires electricity to function. Electricity emits from the positive side of the source, travels along the wire, through the resistors, and back into the negative side of the source.
(sometimes also called
) is the difference of electrical potential between two points of an electrical or electronic circuit, expressed in volts. (Cite: Wikipedia)
The flow of electrical charge, measured in amperes (amps). An ampere is equal to the flow of one coloumb (the International Standard of electric charge) of charge per second.
The degree to which an object opposes an electrical current through it. Pretty much, the amount of electricity it uses up.
Explain how electricity is used to produce heat and light in incandescent bulbs and heating elements.
Incandescence – The release of electromagnetic radiation, usually visible, due to temperature.
The filament of such a bulb is electrically heated to incandescence, and heat and visible light are emitted. The inside of the bulb is airtight to prevent oxidation of the filament, which would rapidly destroy it.
Describe the relationship between current and magnetism.
Current in conductor makes magnetic field
In Diagrams: = current flowing away from you, = current flowing towards you
If you hold a current with your right hand, thumb pointing in the direction of current flow, your fingers will curl in the direction of the magnetic field.
Temporary Magnetic Field mixed with Permanent Magnetic Field
When the magnetic field created by a current is placed in a permanent field, the fields combine to form a field like the one below. There is also a resulting force on the conductor. The force on the conductor is greatest when the current runs perpendicular to the permanent magnetic field. Also, there is no force on the conductor if the current runs parallel with the magnetic field.
Interactions Between Two Temporary Magnetic Fields
Two parallel conductors with currents flowing in the same direction will be attracted to one another. If the two parallel conductors have currents flowing in opposite directions, the two currents will repel one another.
Explain how heat is used to generate electricity.
Turbine – A rotary engine that extracts energy from a fluid flow.
Turbines are driven by the flow of gas heated by the combustion of natural gases, the combustion of coal, utilization of green energy, or output from nuclear energy. They are part of heat engines.
Heat engine – a physical or theoretical device that converts thermal energy to mechanical output.
This creates kinetic energy, which is used to drive a generator.
This past year: University of Utah scientists found a way to turn heat to sound, and then electricity. This is still in production, funded by the US Army.
Describe the availability, current uses and environmental issues related to the use of fossil and nuclear fuels to produce electricity.
The main energy sources used to produce electricity are the fossil fuels
They are formed from the remains of plants and animals that lived and died long time ago- the organic remains were changed into energy-rich substances
Examples are oil, coal and natural gases
Oil is a sticky black liquid usually found trapped within rock layers underground
Coal is a black rock that occurs in layers between other rock layers
Natural gas is commonly found underground with oil deposits.
Fossil fuels have other uses besides produces electricity: heating homes, powering automobiles, cooking, etc
There are many environmental issues with fossil fuels:
The burning of fossil fuels creates air pollution
When fossil fuels are burned, chemicals are released into the air that pose dangers to living things-this is the main cause of acid rain
Transportation of oil and natural gas can lead to accidental oil spills and kill marine wildlife
Pipelines built to transport oil and gas over land may alter the ecology of areas
The burning of any fossil fuels produces carbon dioxide which is a green house gas that traps heat to the earth’s atmosphere which leads to global warming
Environmental issues with coal:
Coal mining is dangerous
Smoke from coal-burning power plants is the main cause of acid rain which is harmful to ecology of lakes and forests
Breathing air containing coal dust can lead to black lung disease
Mining coal also destroys landscape and forests
Environmental issues with nuclear energy:
Nuclear power plants use water from nearby lakes to cool reactors which returns water to the environment several degrees warmer
The increase in temperature is called thermal pollution can be harmful to organisms living in the water
The used-up uranium fuel, known as nuclear waste, is poisonous and radioactive to the environment when dispose
Describe the availability, current uses and environmental issues related to the use of hydrogen fuel cells, wind and solar energy to produce electricity.
Does not cause pollution and is clean and renewable
Expensive to convert into usable form
Not always reliable because it depends on the weather
Does not cause pollution and is clean, inexpensive and renewable
Not practical for large scale power generation
Not always reliable given winds are not always constant
Hydrogen Fuel Cells
Fuel cells convert chemical energy into electricity-it produces electricity from various external quantities of fuel (anode side) and oxidant (cathode side)
These react in the presence of an electrolyte
A hydrogen cell uses hydrogen as fuel and oxygen as oxidant
The fuel cells break apart a molecule of hydrogen into electrons and protons
Two plates are connected by a wire with an electrolyte sandwiched in between
Hydrogen is supplied to one plate and oxygen to the other
They try to bond but only the proton of the hydrogen atom can pass through the membrane
The unification of the hydrogen proton and electron creates water and a small amount of heat
There is plenty of hydrogen in the air
It does not pollute the atmosphere
Have simple construction
Fuel cells are very expensive
Prototype fuel cells only last 1/5th as long as needed to make fuel cells cost-effective
Costs more to produce hydrogen than is earned by using hydrogen in fuel cells
Electricity generated by fuel cells in cars cost thousands of dollars per kilowatt
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