When you turn up the thermostat on your furnace several things happen. which of these would be considered a chemical property of matter?
a) hot air rises
b) fuel can burn in the furnace
c) air moves in a convection current

When you turn up the thermostat, fuel can burn in the furnace this is considered a chemical property of matter.

The burning of fuel in a furnace is a chemical reaction. Burning or combustion is a chemical reaction in which a substance combines with oxygen to produce heat and light.

The burning of fuel in the furnace leads to the production of new substances other than the starting substances. Therefore, burning is a chemical reaction.

Summarily, when you turn up the thermostat, fuel can burn in the furnace this  is considered a chemical property of matter.

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There are really only two choices there ... hot air rising is one PART of a convection current, and convection current happens because of physical properties.

Fuel can burn in a furnace because of its chemical properties. (B)

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s