Freja picks a coin off a sunbaked dashboard and drops it into a glass of cool water. The coin cools; the water warms a little.
The coin shares its energy with the water, every single time. Why does the energy spread instead of staying in the coin?
In earlier grades you saw that temperature measures the average kinetic energy of a thing's particles.
The hot coin's particles move fast. The cool water's particles move more slowly.
At the coin's surface, particles collide, and the collisions pass energy back and forth at random.
Energy shared across the particles of both objects is more spread out than energy concentrated in the hotter one.
So the spread arrangement is the one found, every time anyone looks.
The same reason stands behind the one-way street. Heat never flows from colder to hotter on its own, because that flow would concentrate the energy into a less likely arrangement.
A pizza stone comes out of a hot oven onto a counter in a 21 °C kitchen. Why does its energy spread into the counter and the air instead of staying in the stone?
Energy shared across the stone, the counter, and the air is more spread out than energy concentrated in the stone.
Energy and matter drift toward the arrangement that is overwhelmingly most likely, and spread-out arrangements vastly outnumber concentrated ones.
The energy spreads because the spread arrangement is overwhelmingly the most likely one.
Why does a lukewarm drink never gather heat out of the cooler air around it to reheat itself?
Reheating would concentrate energy into the drink.
Spread-out arrangements vastly outnumber concentrated ones, so the drift never runs toward the concentrated arrangement.
The drink never reheats itself, because the gathered arrangement is overwhelmingly unlikely.
A hot glue gun's metal tip is unplugged in a 20 °C craft room. Where does the tip's extra thermal energy end up?
Why does a hot hair straightener's energy spread into the room instead of staying in its plates?
Keane says: 'Energy shared across the particles of a hot skillet and the kitchen air is more spread out than the same energy concentrated in the skillet alone.' Is he correct?
A laptop charger brick runs warm and is then unplugged in a 21 °C room. Why does its energy spread into the room instead of staying in the brick?
The same amount of thermal energy starts out concentrated in a food cart's hot griddle. After a while, which arrangement of that energy is overwhelmingly most likely?
Which of the following statements explains why heat never flows from a colder object to a hotter object on its own?