1. Will biogas burn with a flame. why?

2. when iron is heated strongly, it becomes red hot and glass but does not burn with a flame. Why?

1 - Biogas is composed of flammable gases such as methane. This means It can combust.

2 - Iron itself cannot catch fire due to it's physical make-up. Metals in general tend to not catch fire.

1. The reason shy biogas burns with a flame is that biogas is a combustible gaseous fuel. Biogas is made up of a mixture of methane (CH4) and carbon dioxide (CO2), along with other trace gases. Biogas is commonly made from animal manure, sludge in wastewater and landfills that contain organic waste.

2. When iron is heated strongly, it becomes red and hot, but it does not burn with a flame. This is because in order for us to be able to burn iron we would have to be able to heat the surface of iron to its ignition temperature. However, when we heat iron, it does not reach its ignition temperature, and therefore does not burn.