We study the effect of a single , instantaneous starburst on the dynamical and chemical evolution of a gas-rich dwarf galaxy , whose potential well is dominated by a dark matter halo .
We follow the dynamical and chemical evolution of the ISM by means of an improved 2-D hydrodynamical code coupled with detailed chemical yields originating from type II SNe , type Ia SNe and single low and intermediate mass stars ( IMS ) .
In particular we follow the evolution of the abundances of H , He , C , N , O , Mg , Si and Fe .
We find that for a galaxy resembling IZw18 , a galactic wind develops as a consequence of the starburst and it carries out of the galaxy mostly the metal-enriched gas .
In addition , we find that different metals are lost differentially in the sense that the elements produced by type Ia SNe are more efficiently lost than others .
As a consequence of that we predict larger [ \alpha /Fe ] ratios for the gas inside the galaxy than for the gas leaving the galaxy .
A comparison of our predicted abundances of C , N , O and Si in the case of a burst occurring in a primordial gas shows a very good agreement with the observed abundances in IZw18 as long as the burst has an age of \sim 31 Myr and IMS produce some primary nitrogen .
However , we can not exclude that a previous burst of star formation had occurred in IZw18 especially if the preenrichment produced by the older burst was lower than Z = 0.01 Z _ { \odot } .
Finally , at variance with previous studies , we find that most of the metals reside in the cold gas phase already after few Myr .
This result is mainly due to the assumed low SNII heating efficiency , and justifies the generally adopted homogeneous and instantaneous mixing of gas in chemical evolution models .