To determine in which case the change in entropy is negative, we need to understand the concept of entropy.$\\$Entropy is a measure of the disorder or randomness in a system. Generally, processes that increase disorder result in an increase in entropy.$\\$Let's analyze each option:$\\$• Option 1: Evaporation of water$\\$Evaporation involves the transition of water from a liquid to a gas. This process increases the disorder as gas molecules are more disordered than liquid molecules.$\\$Therefore, the change in entropy is positive.$\\$• Option 2: Expansion of a gas at constant temperature$\\$When a gas expands at constant temperature, its molecules spread out and occupy a larger volume, increasing disorder.$\\$Thus, the change in entropy is positive.$\\$• Option 3: Sublimation of solid to gas$\\$Sublimation is the transition from a solid directly to a gas. This process significantly increases disorder as gas molecules are much more disordered than solid molecules.$\\$Hence, the change in entropy is positive.$\\$• Option 4: $2H(g) \rightarrow H_2(g) \\$In this reaction, two hydrogen atoms combine to form one hydrogen molecule. The number of gas particles decreases, leading to a decrease in disorder.$\\$Therefore, the change in entropy is negative.$\\$Thus, the correct option is 4, where the change in entropy is negative.