Hank explains why solid water is less dense than liquid water even though solids are typically more dense than liquids. He also discusses how the high heat capacity of water helps support life on Earth. He uses the bodily process of sweating to exemplify water's unique properties.
The monsters measure the capacity of different sized scoops to find the scoops that have enough capacity to fill a bag with different treats. Once they find the right sized scoop, they begin filling the bags with treats. Later, a Monster Monitor further explains capacity by showing a monster's attempts at filling a pool with dragon drool using different sized buckets.
Doc Brown shows Marty his time machine in the DeLorean at the Twin Pines Mall parking lot. Doc tells Marty about the date he invented time travel. He states that the Flux Capacitor is what makes time travel possible.