This paper aims at pushing the clear relationship between software service composition and chemical dynamics a step forward. We developed a coordination model where services and clients are coordinated via a tuple space handling services as if they were interacting chemical substances: on the one hand, services get equipped with an ?activity value? resembling chemical concentration and measuring their reactiveness as imposed by the tuple space; on the other hand, services automatically compose via interaction ports resem- bling chemical bonding. The tuple space enacts a feedback loop that regulates and balances the activity level of (atomic or composite) services, decreasing it over time as in chemical decay, but reinforcing it each time the service is correctly used. This behaviour promotes service competition: losing (i.e. unused) services literally extinguish. Which services or service compositions survive competition is automatically decided solely based on resulting performance, i.e. the rate at which services are actually exploited.