A chemical change means that a new substance was formed. Different from what it was before the change took place.
Flammability and decomposition are examples of chemical changes. <<<This is chemical change. An example can be seen in fruit. When a cut apple stays to long in the open it turns brown. This is because it is oxidized. Even if the apple tastes the same on the molecular level it has changed
Chemical changes involve a rearrangement of atoms to form new substances. <<< It states even in the definition of chemical change that a new substance has to be formed
Chemical changes can often be identified by the formation of a gas or a solid or the release of heat. <<< In a chemical change something extra may be created. This is different from an ice cub melting (which would be physical change). Although it goes from solid to liquid it is still water, and there is no extra product
Nothing is altered at the molecular level during a chemical change. <<<This is false
Hope this helped!