combustion and flame 2

While cooking, if the bottom of the vessel is getting black on the outside, it means that

• the food is not cooked completely

• the fuel is not burning completely

• the fuel has high calorific value

• the fuel is burning completely

The hottest zone in the candle flame is

• non luminous zone

• luminous zone

• invisible zone

• all zones are equally hot

The zone that produces yellow light in the candle flame is

• nonluminous zone

• luminous zone

• invisible zone

• all zone gives light

LPG burns with a

• non luminous flame

• luminous flame

• yellow flame

• both a and b

Burning of charcoal in a closed room will produce

• carbon dioxide

• nitrogen dioxide

• carbon monoxide

• sulphur dioxide

Coal burns with

• flame

• only glow

• both flame and glow

• does not burn

Which part of the flame is hottest

• A

• B

• C

• all of above

Combustion is a

• physical process

• chemical process

• both a and b

• none of these

In presence of water, ignition temperature of paper

• decreases

• increases

• remains constant

• can decrease or increase

Which element shows spontaneous combustion

• Calcium

• Phosphorus

• copper

• Iron