Achieve Week 4 and 5: Q3

[Alondra Cortes 1F]

The textbook defines endothermic reactions as processes and reactions that absorb heat energy, causing the surroundings to cool. But is this always true? For instance, how does the apply to the example of baking a cake? I understand the ingredients absorb the heat coming from the hot air in the oven which is what makes it endothermic. But how does the second part of the definition "causing the surroundings to cool" apply to this example?

[Rachel 1J]

Intuitively, it may not make much sense to think of baking a cake as "cooling the surroundings". However, if you break down the process of an endothermic reaction, it may make more sense. When thinking about baking a cake, you know that it will take heat to bake it - you turn on the oven to add heat to the batter. If a reaction requires heat, it is automatically endothermic. Technically, this means that the system takes heat from the surroundings, causing the surroundings to be cooler. However, this may seem confusing because an oven is hot - however, the heat is being supplied to the surroundings by an external source, so although the "surroundings are cooled" by the endothermic reaction of the cake, the oven is still hot.

[Saahithi Kari]

When it comes to understanding endothermic reactions, it is best to try to break down the process that is actually occurring to help identify whether the reaction is actually endothermic or exothermic. For baking a cake, you are having to add heat to the cake to induce the chemical reaction, which is the baking. As for cooling the surroundings, it is hard to conceptualize that the oven would be losing heat because we always keep it on in order to actually bake. However, if you heated the oven to the desired temperature, placed the cake in, and did not have the oven maintain a constant heat, you would find that the temperature of the cake increased while the temperature inside the oven decreased. In normal life, we leave the oven on and the oven maintains heat through the use of electricity so it doesn't reduce its temperature, but the surroundings are cooling down.

[Dayeon Kim 2D]

When baking a cake it does cause the surroundings to cool but in a very minimal amount and the cake won't ever actually reach the same temperature as the oven before burning but it will continue to absorb heat while it is in the oven, making it an endothermic reaction.

[Anjana Shriram 2A]

It may also be helpful to think of the oven as an isolated system, so any heat gained by the cake ("rxn mixture") is heat lost by the surroundings (oven). In other words, q(cake) = -(q(surroundings)). The cake gains heat when baked, and by the previous statement, whatever heat it gains must come from the surroundings. So, we are taking away heat from the surroundings which can also be described as "cooling the surroundings". Hope this helps!