Physics/Chemistry of Espresso Machines: Part 1

Here’s an activity based on observing espresso machines in action. Watch the following video showing the milk steaming container (with a short sidetrack to the espresso pot).

What do you notice about the milk as it steams? Can you explain what is happening?

Diagram showing how steam and water escape the water tank at two different locations.Here are some details of how this espresso machine works:

  • The water boiling tank is filled about ¾ of the way up with water.
  • From the bottom of the water tank, a tube runs upward to the coffee holder, where the water is forced through the coffee grounds and drips down into the espresso pot.
  • At the top of the water tank, a tube leads outside to the steamer jet, which is placed in the milk steaming container.

The answers aren’t here, you need to develop them yourselves 🙂

Hints below ↓

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Notice that for the first 20-30 seconds, there are bubbles forming, but after that there are no more bubble forming.

More hints below ↓

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What is in the space above the water when the machine first starts? What is in that space after 20-30 seconds?

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