From the Black Hole Bistro: Hot soup, hotter spoon?

Here’s a bit of physics to contemplate as you slurp your soup. Which is hotter: the ceramic bowl or the metal spoon?

Since we’re slurping at Perimeter, we know that if the spoon, the bowl, and the soup are all in contact with each other, they will come to thermal equilibrium. Assuming the soup has been sitting for a bit, the soup, bowl, and spoon should all be at the same temperature.

But they sure don’t feel that way. The ceramic bowl will feel pleasantly warm, whereas the spoon might burn your tongue. What gives?

Short answer: what we feel is not temperature, but the rate at which heat flows into our hands. That depends on both the object’s temperature and its thermal conductivity. The thermal conductivity of metal is high, while the thermal conductivity of ceramic is low.

This also works in reverse, which is why a cold piece of metal feels much colder than a cold piece of wood. (Thus, Perimeter’s winter visitors should not lick flagpoles. It is not a Canadian tradition, no matter what you’ve heard.)

LENTIL AND CHORIZO SOUP

2 chorizo sausages, finely chopped
1 brown onion, finely chopped
2 garlic cloves, crushed
1 tbsp sweet paprika
1 carrot, peeled, finely chopped
1 zucchini, finely chopped
1 tomato, finely chopped
4 cups (1 litre) chicken stock
400 gram can of lentils, rinsed, drained
Crusty bread, to serve
Basil oil
1/3 cup (80 mL) olive oil
1/4 cup chopped basil

Heat a large saucepan over high heat. Add the chorizo and cook, stirring, for 2-3 minutes or until brown all over. Use a slotted spoon to transfer to a bowl.

Add the onion, garlic, and paprika; cook, stirring, for 5 minutes or until onion softens. Add the carrot, zucchini, and tomato; cook, stirring, for 2 minutes or until tender.

Add the chicken stock and chorizo; bring to a simmer. Cook, stirring occasionally, for 15 minutes or until vegetables are tender and soup thickens slightly. Add the lentils; stir to combine. Taste and season with salt and pepper.

Place the oil and basil in a blender and blend until smooth. Strain through a fine sieve into a jug.

Ladle soup into serving bowls. Drizzle with basil oil and serve with crusty bread.