Answers to Conceptual Connections

1 The correct answer is (a). When A sys is negative, energy flows out of the system and into the surroundings. The energy increase in the surroundings must exactly match the decrease in the system. 

2 (a) heat, sign is positive (b) work, sign is positive (c) heat, sign is negative 

3 Bring the water it has the higher heat capacity and will therefore release more heat as it cools. 

6 An endothermic reaction feels cold to the touch because the reaction (acting here as the system) absorbs heat from the smroundings. When you touch the vessel in which the reaction occius, you, being part of the surroundings, lose heat to the system (the reaction), which makes you feel cold. The heat absorbed by the reaction (from your body, in this case) does not increase its temperature, but rather becomes potential energy stored in chemical bonds. 

4 (c) The specific heat capacity of substance B is twice that of A, but since the mass of B is half that of A, the quantity m X Cj will be identical for both substances so that the final temperature is exactly midway between the two initial temperatures. 

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