A reaction is occurring in a test tube. How is heat transmitted to the surroundings?
All of the heat escapes out of the open top of the test tube as molecules collide with the air.
As bubbles are formed and gas escapes, the heat is carried with the rising bubbles.
Heat is carried out with matter as matter is changed with the surroundings.
Molecules collide with the glass, and the glass molecules then transmit that energy to the outside.