A. Study which factors are related to the evaporation rate of liquid, and apply the control variable method; B, introducing the concepts of light and magnetic induction lines by model method; C. The magnetic field is invisible and intangible. We can know it through the effect of the magnetic field on the small magnetic needle put in, and use the conversion method; D. When learning the microstructure of solids, liquids and gases, analogy is used for students who are in class, students who are walking in the classroom after class, and students who are free to move on the playground during class.
Therefore, choose c;
(3) When heating from the bottom, water will circulate, and the temperature of water will be rapidly increased. This phenomenon is called convection, which can occur in various gases and liquids.
According to the above research, if you plan to install a radiator at home in winter, you should install it at the bottom of the room to get the best heating effect.
So, the answer is: (1) c; (3) increase; Bottom.