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| A great deal of stored energy is suddenly converted to heat in a confined space. The rapid conversion to heat is the heart of most explosions. |
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| What causes damage in an explosion? |
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| Something that raises the temperature of a material, as measured by a thermometer. (Heat is actually the microscopic energy of motion of vibrating molecules) |
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| (With a capital C) The famous food Calorie, which is 1000 cal = 1 kilocalorie. |
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| Unit of energy, equal to 1000 Calories |
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| Unit of energy. There are 4200 Joules in a Calorie. |
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| What makes TNT so destructive if chocolate chip cookies have more energy? |
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| It has high power - it can release its energy very, very quickly. |
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| How is gasoline used as fuel in cars? |
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| Gasoline must be mixed with oxygen to explode; in cars, this is done by a fuel injector (older cars have carburetors). The explosion takes place in the cylinder, and the enrgy then pushes a piston down the axis of the cylinder driving the wheels of the car. |
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| Typical automobile battery. |
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| What are the benefits and downsides of battery powered cars? |
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| They are efficient, somewhat cheaper, but batteries take up space, can only go low speeds, batteries must be replaced |
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| What are the benefits and downsides of electric cars? |
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| They can go fast, charge from home to drive at 1-2 cents per mile, but cost around $100,000 because lead acid batteries are so expensive, plus you must add replacement costs so it's actually 10 times the cost of gasoline. |
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| What are the benefits and downsides of hybrid autos? |
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| Good gas mileage, batteries last longer, but upfront costs are more than that of regular cars. |
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| Benefits and downsides of hydrogen as a fuel? |
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| Hydrogen is dangerous to store, and takes up a lot of space ( could only be used for buses, trucks, planes. Hydrogen is not a source of energy, but a means of transporting energy. And although the fuel cell produces no pollution (only water), the plant used to produce the hydrogen does not. It poses potential environmental risks and destroy the ozone layer. |
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| Energy stored in the forces between parts of the atomic nucleus, released when the nucleus is broken. |
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| energy that an object has at high altitude, when it falls, this energy is converted to kinetic energy. |
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Energy used per second (rate of energy transfer)
P=energy/time |
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| Benefits and downsides of solar power? |
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| It is sustainable in the sense that as long as the sun is shining, we can use its energy - must find a way to store during night/cloudy days. A cheap solar cell can only convert about 15% of the power, and the rest is reflected or converted to heat. It's also impractical and solar cells are expensive and don't last forever. |
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| What are the upsides and downsides of solar powered automobiles? |
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| Since solar cells are only 40% efficient at best, cars must be large just to be able to move - can't go fast at all. |
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| Benefits and downsides of wind power? |
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| They are unattractive, take up lots of space, kill wilderness areas, kill birds, noisy, only work when wind is blowing, but no pollution. |
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| What is the kinetic energy equation? |
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| What are smart rocks and brilliant pebbles? |
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| A rock with a computer programmed to get in the path of a nuclear missle, preventing it from reaching target. Brilliant pebbles are smaller versions of this with smarter computers. |
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| What caused the demise of the dinosaurs? |
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| An asteroid hit earth, creating an enormous explosion releasing heat and throwing a layer of dirt into the atmosphere which blocked sunlight over earth for many months, stopping plant growth and starving animals. |
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| This number represents the number of protons in an atom, also the number of electrons in the atom (usually). |
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| Combinations of atoms that stay clumped together. |
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| When molecules break apart or come together |
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| How fast do molecules shake? |
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| The typical velocity is the same as the speed of sound, about 700 miles per hour. |
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| Even though you can't see atoms, you can see the effect their shaking has on small, visible particles. With a microscope, you can see the shaking of tiny bits of dust known as brownian motion - the dust is hit on all sides by air molecules, and if the dust is sufficiently small, the bombardment does not average out. |
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| How does sound travel through air? |
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| It travels through air by molecules bumping into each other - so the speed of sound is determined by the speed of molecular motion, which makes the speed of sound approximately the speed of molecules. |
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| For every ___ seconds, lightening is ___ miles away |
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| What is the speed of light? |
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| 1 foot in 1 computer cycle (ns) |
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| What happens when kinetic energy is turned into heat? |
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| We can think of this as coherent, regular motion being randomized - molecular energy changes from being neatly "ordered" to being "disordered" - amount of disorder is called entropy |
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| Amount of disorder - when heat flows, the net entropy of the universe increases. |
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| What causes the white noise on TV's |
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| Electrons jumping around in the electronics of your set. |
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| A measure of the hidden kinetic energy of the molecules. |
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| At the same temperature, what molecules move faster? |
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| Lighter moves faster than heavier. |
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| At the same temperature, what molecules move faster? |
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| Lighter moves faster than heavier. |
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| Zeroth Law of Thermodynamics |
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| Objects in contact tend to reach the same temperature. |
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| Why is there no hyrdrogen in Earth's atmosphere? |
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| It's lighter than nitrogen and oxygen, so it would have a higher velocity and escaped. Our gravity is too weak to keep it here. |
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| Eventually, the stars will stop burning and everything in the universe may reach the same temperature, -270 C or even colder if you factor in expansion. |
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| The temperature when all molecules come to a stop and have zero kinetic energy. This happens at -273 C = -459 F. It doesn't depend on the kind of material. |
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| How do you convert from Kelvin to Celsius scale? |
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| When temperatures are really high, the temperature in C is approximately ___ |
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| Most solids _____ when heated |
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| How will global warming affect sea level? |
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| Water will expand, flooding much of the coastal areas of the world. |
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| How do bimetallic strips work? |
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| As one side expands more than the other, the strip bends resulting in expansion, sliding the indicator over a temp scale. |
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| How do digital thermometers work? |
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| They take advantage of the electrical properties of certain materials changing with temperature changes. |
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| What happens to cold water when it's cooled? |
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| It expands! Even when it's in a liquid state before forming a solid. |
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| The zeroth law implies that the _____ object will lose some of its kinetic energy, and the _______ object will gain some. |
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| What are the four states of matter? |
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| Solid, liquid, gas, plasma |
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| The change from a solid to liquid is called a change in ___ |
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| At extremely hot temperatures, collisions between molecules are sufficient to break them into individual atoms, and if the atoms themselves are broken apart so that electrons are knocked off their surfaces, then we call the gas a plasma -- conssts of electrons with a negative charge. |
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| At extremely hot temperatures, collisions between molecules are sufficient to break them into individual atoms, and if the atoms themselves are broken apart so that electrons are knocked off their surfaces, then we call the gas a plasma -- conssts of electrons with a negative charge. |
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| An engine that runs by turning heat into mechanic motion |
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