Heat means that when the change of system state comes from the destruction of thermal balance conditions, that is, from the temperature difference between the system and the outside world, we say that there is thermal interaction between the system and the outside world. As a result, energy is transferred from a high-temperature object to a low-temperature object, and the transferred energy is called heat. Heat and work are two different forms of energy transfer with the change of system state, and they are the measures of different forms of energy transfer. They are all related to the intermediate process of state change, so they are not functions of system state.

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Toast is a transliteration of English toast, which is called toast in Cantonese. In fact, it is a kind of bread can with or without cover made of rectangular baking cans.

Cut the covered toast into squares and put ham or vegetables in it. Bread baked in a baking pot without a lid is a rectangular dome shape, similar to rectangular bread.

Toast bread is a kind of western bread, which is common in breakfast in Europe and America, and also in tea restaurants in Hong Kong. The raw material is square bread, which is baked with a toaster (called "toaster" in Hong Kong) until it tastes delicious. Take it out, coat one side of the square bread with ingredients such as cream, butter and jam, and sandwich two square buns. This is hot food.