1Two things to know first
Same start, but mixing isn't nothing
You need two small ideas. Watch each one happen:
They start the same
Two jars on the same shelf reach the same room temperature — neither is warmed or chilled. The thermometers match.
Mixing rearranges them
When the two liquids meet, their tiny bits grab onto new partners. Snapping into new pairings can let energy out — or pull it in.
2Two ways it can go
Letting heat out vs. swallowing heat
Heat comes out 🔥
Some new pairings snap together hard and spill energy as heat — the cup warms up, like a hand-warmer packet.
Heat gets pulled in ❄️
Other pairings need energy to break apart, so they borrow heat from the liquid itself — the cup turns cold, like an ice-pack. Keep this in mind…
3Pour the first pair
Tip the warm pair in and watch the line
Here's the "snap-together" pair. Both liquids start right at room temperature (the line sits in the middle). Slide to pour them together and watch the big thermometer.
Nothing was heated. The bits just snapped into new pairings and spilled their leftover energy as heat — so the line climbs and steam wisps off.
4Now the mystery pair
Two different liquids — still room temperature 🧪
New jars, same shelf, same starting temperature as before. But these two grab partners in a different way. Guess what the thermometer does, then pour.
Guess before you pour
You stir these two room-temperature liquids together and stick a thermometer in. What does it read?