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Daily Science pg. 40

Daily Science pg. 40. Convert the following temperatures: 45 o C into Kelvin 45 o C into Fahrenheit 309 K into Fahrenheit 98 o F into Kelvin 299 K into Celsius 8 o F into Kelvin

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Daily Science pg. 40

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  1. Daily Science pg. 40 • Convert the following temperatures: • 45oC into Kelvin • 45o C into Fahrenheit • 309 K into Fahrenheit • 98oF into Kelvin • 299 K into Celsius • 8oF into Kelvin • Give an example of conduction, convection, and radiation. Explain why over exposure to the sun or to X-rays can be harmful. • Calculate the kinetic energy of a wheel that has a mass of 65 kg and is rolling with a velocity of 4.5 m/s. • Calculate the potential energy of a bomb that is falling from a height of 48 m and has a mass of 15 kg. • Calculate the potential energy of a ball dropped from E-wing that weighs 4.8 N and is being dropped 6 m. • Calculate the mass of a person in a wheelchair if they are rolling at a velocity of 0.7 m/s and have 20 j of kinetic energy.

  2. Specific Heat Pg. 41

  3. Conductors and insulators • Conductor- a material through which energy can be transferred as heat. • Examples: • Insulator- a material that transfers energy poorly. • Examples:

  4. Specific Heat • The amount of energy needed to change the temperature of a substance by a certain amount is what determines if a substance will be a good or poor conductor. • Specific heat is the quantity of heat needed to raise the temperature of 1 kg of substance by 1 K. • Specific heat is a physical property.

  5. Specific heat values • Every substance has a unique specific heat. • The letter C is used to denote specific heat. • Water has one of the highest specific heat values (4,186 J/kg x K)

  6. Calculating Specific Heat • Heat= mass x temperature change x specific heat value • Q = m x ∆T x C • Units: • Mass- • Temperature- • Specific Heat- • Heat-

  7. Practice Problems • How much energy is needed to increase the temperature of 0.755 kg of iron from 283 K to 403 K? • How much energy must a refrigerator absorb from 225 g of water to decrease the temperature of the water from 35oC to 5oC?

  8. State changes • Heat makes objects change state. • Energy of a substance either raises the substance’s temperature or changes the substance’s state. NOT BOTH AT THE SAME TIME. • This is why there are horizontal lines on a phase change diagram.

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