It is the verbs in a sentence that determine its tense. This is because stories were traditionally told using the past tense. This made the narrator sound as if they were narrating events from a ...
The past tense is used for things that have already happened. He was sticky. The present tense is used when something is happening now or when something happens regularly. He is sticky.
For example, the tense may change between the methods section and the discussion section. The abstract is usually in the past tense due to it showing what has already been studied. Example: “This ...