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Warm-up 1/31/14

Warm-up 1/31/14 . Q1) What makes an element distinct? Q2) What determines the state of a compound? Q3) How many protons, neutrons, and electrons does P -3 have? .  Number of protons.  Temperature.  protons = 15.  neutrons = 16.  electrons = 18 . HEAT!.

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Warm-up 1/31/14

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  1. Warm-up 1/31/14 Q1) What makes an element distinct? Q2) What determines the state of a compound? Q3) How many protons, neutrons, and electrons does P-3 have?  Number of protons  Temperature  protons = 15  neutrons = 16  electrons = 18

  2. HEAT!

  3. Heat: Energy that transfers from one object to another because of differences in temperature. Temperature: Average kinetic energy of molecules and is measured in Celsius (C) 0  C = freezing water; 100  C = boiling water; 25 C is room temperature. Used around world and with scientist. Fahrenheit (F) 32 F = freezing water; 212F = boiling water TF = 9/5 * TC + 32 Used only in USA. Kelvin (K) [0 K = absolute zero] TK = TC + 273. It is the SI unit for Temperature.

  4. Temperature is measured with a Mercury or colored alcohol thermometer which expands and contracts with changing temperature. Heat is measured in units of calories (cal) or Joules (J). 1 food calorie = 1000 calories Thermal equilibrium - Heat flows from high temperature to low temperature until both objects have the same temperature.

  5. Question • What happens when you put a paper cup over a flame? b) What happens when you fill the cup with water. Why? If you put water in the cup then the cup will not burn. The water and the cup must be at the same temperature so the water will boil before it burns.

  6. Specific heat (c) The quantity of heat needed to raise the temperature of a substance by 1C. Water has a VERY high heat capacity making it hard to heat up and cool. Q = mcΔT Q = heat (measured in Joules) m = mass(measured in kilograms) c = specific heat (listed on a table given to you) ΔT = change in Temperature (Celsius or Kelvin)

  7. Question • A piece of tile and a piece of wood sit in a room, which one is colder? b) 2 pieces of ice sit on different blocks, which one melts first and why? The tile is colder and will melt the ice faster because the tile has a lower specific heat therefore it warms and cools easier.

  8. Water has one of the highest capacity for storing energy. Because of this water is used as a cooling agent for cars and engines. This high heat capacity is what keeps Houston at a moderate temperature. Or swimming pools cool on a hot day.

  9. Example; A 5.10 kg cast iron skillet is heated on the stove from 295K to 450K. How much heat had to be transferred to the iron? Specific heat of iron = 450 J/(kg*K) m = 5.10 kg T = 450K – 295K = 155K c = 450 J/(kg*K) Q = ? Q = mc T Q = 5.10 kg * 450 J/(kg*K) * 155K Q = 356,000 J or 356 kJ

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