(2) The burning of cigarettes can release heat, thus increasing the temperature of combustible materials. When the ignition point of combustible substance is reached, combustible substance will burn.
Therefore, the answer: make combustible materials reach the combustion temperature;
(3) When aluminum reacts with oxygen in the air, a dense alumina protective film is formed on the surface, so the answer: When aluminum reacts with oxygen in the air, a dense alumina protective film is formed on the surface;
(4) The main component of ink is carbon black, which is a simple substance of carbon. The chemical properties of carbon are relatively stable at room temperature, so the answer: the chemical properties of carbon are stable at room temperature.