Lead melts at 328 ℃. How much heat is required when 23.0 g of solid lead at 297 K condenses to a liquid at 702 K?

Heat = 1.74 kJ

Given

melts at 328 ℃ + 273 = 601 K

mass = 23 g = 0.023 kg

initial temperature = 297 K

Final tmperature = 702 K

Required

Heat

Solution

1. raise the temperature(297 to 601 K)

c of lead = 0.130 kJ/kg K

Q = 0.023 x 0.13 x (601-297)

Q = 0.909 kJ

2. phase change(solid to liquid)

Q = m.Lf (melting/freezing)

Q = 0.023 x 23 kj/kg = 0.529 kJ

3. raise the temperature(601 to 702 K)

Q = 0.023 x 0.13 x (702-601)

Q = 0.302 kJ

Total heat = 1.74 kJ

gravity causes stares to cluster i think so

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.