Check my answers . 1. a copper block (20c) is placed in contact with a lead block (30c), which is already in contact with an iron block (70c). which of the following will happen? a) heat will flow from the copper to the lead and from the iron to the lead until the temperatures are equal. b) heat will flow from the iron to the lead and from the lead to the copper until the temperatures are equal. c) heat will flow from the copper to the lead to the iron until the temperatures are equal. d) heat will flow from the lead to the copper and to the iron until the temperatures are equal. i think the answer is b.

The correct answer is statement B, that is, the heat will flow from the iron to the lead and from the lead to the copper until the temperatures are equal.  

On the basis of Zeroth law of thermodynamics, when the two systems are in thermal equilibrium with the third system then all of them are in thermal equilibrium with each other. Thus, when the copper block is placed in next to lead block and lead block is placed in next to iron block then heat will flow from hotter block to the colder block.

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

b) mutualism

hope this : )