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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.

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Presentation on theme: "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."— Presentation transcript:

1 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  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 35 o C to 5 o C?

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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