Which answer best defines physical property

What mass of natural gas (ch4) must you burn to emit 276 kj of heat?

Answer explain why it is not possible to deduce a complete order of reactivity.

You exhale co2 which is produced during cellular respiration.  co2 combines with the water in your blood's plasma to make up one half of the body's most important buffer pair, carbonic acid.  the more physical activity you engage in, the more co2 your body is producing.  you can see this by putting some of the cabbage indicator in a glass and then blowing bubbles into it through a straw.  can you see a change in the color of the indicator?