science 10 physocs

Energy Energy forms can be transferred into an object or transformed into an object System anything under observation surrounding anything that’s not system. universe = system + surroundings 

kinetic engergy Mechanical kinetic energy: energy of an object that is in motion  Radiant energy: energy of electromagnetic waves from an energy source (UV, solar visible light, infrared)Thermal energy: energy of random motion of particles in a substance (heat)  Sound energy: energy of vibrations of particles Electrical kinetic energy: energy of electrons moving along a wire (electricity, lightning)

Potential energy:the stored energy of an object as a result of its condition or its position Elastic potential energy: energy stored in a stretched or compressed object (elastic band, rubber shoes, ball, spring) Chemical potential energy: energy stored in chemical bonds (fossil fuels, food, oil, gasoline) Gravitational potential energy: energy due to the position of an object  Nuclear energy: energy stored in the nucleus of an atom  Electrical potential energy: energy stored by a separation of positive and negative charges Magnetic potential energy: energy stored in a magnetic field

Law of conservation of energy: law stating that energy is neither created nor destroyed, but is transformed from one form of energy to another or transferred from one object to another. When energy is transferred, it stays in the same form. When energy is transformed, it changes into another form of energy. When energy transformations occur, some of the energy is converted into a form that is not useful and it is considered to be “ lost ” There are three types of systems:Open system: a system that can exchange both energy and matter with its surroundings Closed system: a system that can exchange only energy but not matter with its surroundings  Isolated system: a system that cannot exchange energy nor matter with its surroundings

Nuclear Physics Isotopes Radioactivity: the release of high-energy particles and rays of energy from a substance as a result of changes in the nuclei of its atoms  Radiation: high-energy rays and particles emitted by radioactive sources (radio waves, microwaves, infrared rays, visible light, and ultraviolet rays) Light: a form of radiation that humans can see 

Radioactive Decay By emitting radiation, atoms of one kind of element can change into atoms of another element Radioactive atoms emit radiation because their nuclei are unstable Unstable atoms gain stability by losing energy Radioactive decay: the process in which unstable nuclei lose energy by emitting radiation Unstable radioactive atoms undergo radioactive decay and form stable, non-radioactive atoms, usually of a different element Radioisotopes: natural or human-made isotopes that decay into other isotopes, releasing radiation The three major types of radiation are alpha radiation, beta radiation, and gamma radiation Alpha decay: The emission of an alpha particle (the same particles found in the nucleus of a helium atom)Beta decay: A neutron changes into a proton and a beta particle (an electron ) The proton remains in the nucleus while the electron leaves the nucleus Since the proton remains in the nucleus,the atomic number of the element increases by one—it has become an atom of the next higher element on the periodic table; however, its mass number does not change, as a proton of almost equal mass has replaced the neutron Gamma decay: Gamma decay results from a redistribution of energy within the nucleus Gamma radiation consists of rays of high-energy, short-wavelength radiation A gamma ray is given off as the isotope changes from a high-energy state to a lower energy state An “*” means that the nucleus has extra energy that is released as a gamma ray


 Half-life: a measure of the rate of radioactive decay for a given isotope It is equal to the time required for half the nuclei in a sample to decay; its value is a constant for any radioactive isotope The shorter the half-life is, the faster the decay rate Decay curve: a curved line on a graph that shows the rate at which radioisotopes decay Parent isotope: an isotope that undergoes radioactive decay Daughter isotope: the stable product of radioactive decay The production of a daughter isotope can be a direct reaction or the result of a series of decays

Nuclear Reactions

Nuclear fission: a nuclear reaction in which a nucleus breaks apart, producing two or more smaller nuclei, subatomic particles, and energy Heavy nuclei tend to be unstable because of the repulsive forces between their many protons In order to increase their stability ,atoms with heavy nuclei may split into atoms with lighter nuclei The fission of a nucleus is accompanied by a very large release of energy Fission is the source of energy for all nuclear power generation used today; however,the radioactive daughter products are a significant waste disposal problem Nuclear reaction: a process in which an atom’s nucleus changes by gaining or releasing particles or energy A nuclear reaction can release protons ,neutrons , and electrons , as well as gamma rays In nuclear reactions, a small change in mass results in a very large change in energy Scientists can induce , or cause, a nuclear reaction by making a nucleus unstable ,causing it to undergo a reaction immediately Bombarding a nucleus with alpha particles, beta particles, or gamma rays induces a nuclear reaction When some nuclei undergo fission, they release subatomic particles that trigger more fission reactions; this ongoing process in which one reaction initiates the next reaction is called a chain reaction The number of fissions and the amount of energy released can increase rapidly and lead to a violent nuclear explosion ;uranium-235, which is used in Canadian nuclear reactors , undergoes such a reaction Keeping the chain reaction going in a nuclear power plant, while preventing it from racing out of control , requires precise monitoring and continual adjusting Nuclear equation: a set of symbols that indicates changes in the nuclei of atoms during a nuclear reaction The following rules can be used when you write a nuclear equation:The sum of the mass numbers on each side of the equation stays the same The sum of the charges (represented by atomic numbers) on each side of the equation stays the same Nuclear fusion: a nuclear reaction in which small nuclei combine to produce a larger nucleus; other subatomic particles as well as energy are released in this process Fusion occurs at the core of the Sun and other stars where sufficient pressure and high temperatures cause isotopes of hydrogen to collide with great force ; this forces two nuclei of hydrogen to merge into a single nucleus, releasing an enormous amount of energy

Earth’s Energy

Earth’s Energy

• Winds, weather, tides, currents, volcanic activ-ity, and mountain formation on Earth are all due to energy transformations Solar energy, gravitational potential energy, and nuclear energy all play important roles in Earth’s system Solar energy has the greatest impact on Earth Its transformations drive water movement through the atmosphere and the hydrosphere Nuclear energy is transformed into thermalenergy inside Earth’s crust This thermal energy drives tectonic plates to move and is the source of volcanic activities Gravitational potential energy is used to produce electricity The Moon’s gravitational potential energy is the reason why tides exist on Earth The Sun’s solar energy consists of visible light,infrared radiation, and ultraviolet radiation When visible light is absorbed by Earth’s surface, it is converted into thermal energy The atmosphere absorbs infrared radiation and traps it as thermal energyInfrared radiation plays the largest role in regulating Earth’s temperature The rest of the solar energy is absorbed, reflected, and scattered by clouds and the atmosphere  Sensible heat: heat exchanged by a body in which the exchange of heat changes the temperature of the body Latent heat: heat exchanged by a body during a constant-temperature process (phase transition ) Greenhouse gases warm Earth’s atmosphere and contribute to the greenhouse effect Greenhouse gases include carbon dioxide, water vapour, nitrous oxide ( dinitrogen monoxide ), and methane • Without the natural greenhouse effect, the average temperature of the Earth would be−18 ◦C Conduction: the transfer of thermal energy between two substances that areTouching  Collision of molecules in the water and land transfer thermal energy to molecules in the air through conduction Convection: the transfer of thermal energy by the movement of heated fluids from one place to another Convection occurs in the air and distributes thermal energy Water moves among the hydrosphere, geosphere, and atmosphere through: condensation :releases thermal energy into the atmosphere precipitation : water returns to the surface as rain andsnow evaporation : when water absorbs thermal energy and leaves Earth’s surface transpiration : plants take up water from the ground and release it into the atmosphere as water vapour Greenhouse gases are causing Earth’s atmosphere to become warmer This is leading to the increase in ocean temperature as well As a result, aquatic ecosystems are being destroyed and aquatic animals are dying  Terrestrial ecosystems are negatively impacted by the increase in radiation exposure • Radioactive materials and wastes that accumulate in the soil are contaminating terrestrial ecosystems  Harmful effects are seen as a result of Mutations Water absorbs a lot of energy through Evaporation  Evaporation plays a role in cooling Earth Specific heat capacity: the amount of energy required to change the temperature of 1 g of a substance by 1 ◦C  Water has a high specific heat capacity;therefore, ocean temperatures stay relatively constant




Lots of forms of energy, can be transferred into object or transformed into another energy system  anything under observation surroundings all not system universe = system + surroundings  kinetic energy  mechanical ke object that is moving/ motion eg car moving radiant energy  electromagnetic waves eg visible light thermal energy motion of particles heat sound energy vibrations of particles sound electrical ke  electrons moving on a wire