HOMEWORK EXAM 1 CHEM 142 QUESTIONS AND ANSWERS GRADED A

HOMEWORK EXAM 1 CHEM 142 QUESTIONS AND ANSWERS GRADED A Is there an attraction between two neutral helium atoms? Explain in detail why or why not. Be sure to include any evidence you have for your claim and how this supports your reasoning. Yes; 2 helium atoms can be attracted because the electrons in the electron cloud are freely moving. This leads to one of the atoms becoming an instantaneous dipole, this will then induce a dipole on the other atom. The opposite partial charges will attract one another. The force of attraction is called LDFs explain two helium atoms as they approach one another, and explain what is happening. In phase one, the two atoms exist with fluctuating electron clouds. In phase two, one He atom forms an instantaneous dipole when at any given time the electrons exist near one side of the atom. In phase three, the instantaneous dipole induces the other He into forming another dipole and the partial charges attract each other System of dye and water molecules. As the number of molecules in the system increased, the number of distinguishable arrangements for those m olecules increased. The number of "unmixed" arrangements? A. increased B. decreased C. stayed the same The number of "mixed" arrangements? A. increased B. decreased C. stayed the same unmixed- C mixed- A Once the dye molecules are mixed up with the water molecules, they will not "unmix". Why? Since there are many more arrangements in which the molecules are in a mixed state than an unmixed one. Thus the probability that the molecules will be in a mixed state is much greater. As the number of molecules increases, so does the number of different (mixed) arrangements. Suppose you have two copper blocks at different temperatures. What will happen if the two blocks come in contact with each other? The heat transfers from the hot block to the cold block because energy always moves from hot to cold. The cold block will absorb the heat and get warmer. Ultimately, both blocks will have the same temperature. When the two blocks contact each other, what happens to the temperature of each block? What happens to the number of quanta on each block? The hot block will transfer energy to the cold block, until both blocks are at the same temperature. When two blocks come into contact with each other, two quanta are transferred from the hot to cold block. What happened to the number of distinguishable arrangements for the quanta when they went from being unevenly distributed to being evenly distributed across the blocks? A. increased B. decreased C. stayed the same A Remember that when the quanta are unevenly distributed across the blocks there are 840 distinguishable arrangements for the quanta, but when they are evenly distributed there are 1225 distinguishable arrangements. Use this to explain WHY thermal energy transfers from the hot to cold block. Since, in the instance in which quanta are evenly distributed, there are 1225 distinguishable arrangements and that is much more than 840 (the number of arrangements from an uneven state) it is much more likely