phase diagram

[Lily Sperling 1E]

Why does a lower heat capacity equate to a higher slope? Shouldn't it be the opposite?

[Hazem Nasef 1I]

I'll assume you are talking about heating curves since that is what is relevant to heat capacity. Since the x-axis is time, and the y-axis is temperature, a steep slope would mean it takes less time to reach a certain temperature than a slope that isn't steep. If something requires less time to reach a certain temperature, it follows that it requires less energy, therefore having a lower heat capacity.