Simply put, density is how tightly “stuff” is packed into a defined space.
For example, a suitcase jam-packed with clothes and souvenirs has a high density, while the same suitcase containing two pairs of underwear has low density. Size-wise, both suitcases look the same, but their density depends on the relationship between their mass and volume.
Mass is the amount of matter in an object.
Volume is the amount of space that an object takes up in three dimensions.
Density is calculated using the following equation: Density = mass/volume or D = m/v.
If something is heavy for its size, it has a high density. If an object is light for its size it has a low density.
The relative densities of an object and the liquid it is placed in determine whether that object will sink or float.
The question is incomplete. The complete question is :
A common "rule of thumb" for many reactions around room temperature is that the rate will double for each ten degree increase in temperature. Does the reaction you have studied seem to obey this rule? (Hint: Use your activation energy to calculate the ratio of rate constants at 300 and 310 Kelvin.)
Solutions :
If we consider the activation energy to be constant for the increase in 10 K temperature. (i.e. 300 K → 310 K), then the rate of the reaction will increase. This happens because of the change in the rate constant that leads to the change in overall rate of reaction.
Let's take :


The rate constant =
respectively.
The activation energy and the Arhenius factor is same.
So by the arhenius equation,
and 




Given,
J/mol
R = 8.314 J/mol/K





∴ 
So, no this reaction does not seem to follow the thumb rule as its activation energy is very low.
the fire spreading is what represents the form of heat transferring from one atom to another within an object and direct contact