Have you ever wondered why some surfaces outside are hot and others are less hot? This unit begins with a shared experience of observing how surfaces feel hot and less hot outside around the schoolyard. Then students make and record observations of different surfaces in different places in their schoolyard. They compare those observations with their classmates’ to identify patterns to answer their questions about what causes some surfaces to feel hot and others to feel less hot. Students use drawings to explain and share what they figure out about this phenomenon. Students then use their observations to identify the problem that blacktop can get too hot and be uncomfortable to play on. They brainstorm solutions to this problem based on their investigations, draw design solutions, and collaboratively build and test their designs. Students end the unit by creating a class consensus design based on their comparisons of the design features and materials that work best to prevent the blacktop from getting too hot.