A teacher has found two wh te powders on a desk in the chemistry laboratory. She wants to test to see if they are pure substances, so she
measures the melting points. Substarce X meits at 1225C and substance Y
meits between 87 and 93°C. Explain which one is the pure substance.

100 grams of molten lead (600°c) is used to make musket balls. if the lead shot is allowed to cool to room temperature (21°c), what is the change in entropy (in j/k) of the lead? (for the specific heat of molten and solid lead use 1.29 j/g⋅°c; the latent heat of fusion and the melting point of lead are 2.45 × 104 j/kg and 327°c, respectively.)