It is important to take note of th temperature in determining the density of a substance because this will set as a basis and will likely be a variable in the experiment because this will also contribute on the effects of the experiment and a basis of how the experiment has turned to be that way.
Ductility - a materials ability to stretch, ie if you pull it apart does it stretch to a wire.
density - ratio of volume to mass
conductivity - materials ability to conduct a current.
hopefully with these definitions you can figure out the answer.
Through pH scale. it measures the acidity of a substance, pH is measured with a litmus paper, if the paper turns red then it is acidic.
Answer:

Explanation:
Hello,
In this case, we can consider that the given heat of combustion is indeed the heat of reaction since it corresponds to the combustion of propane, which is computed by using the heat formation of all the involved species as shown below:

Thus, since the heat of formation of gaseous carbon dioxide is -393.5 kJ/mol, water -241.8 kJ/mol and oxygen 0 kJ/mol, the heat of formation of propane is:

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