Dry ice is particularly useful for freezing, and keeping things frozen because of its extreme low temperature. And because it sublimates at room temperature, it is also good for producing smoke effect.
Do note that the 1Kg dry ice weight is correct at the warehouse departure time. It is not guaranteed that what arrives at the delivery location is 1 Kg. It is advisable to order a minimum of 6 Kg block dry ice to reduce the likelihood of substantial sublimation.