Explanation: Use "ser" for professions and permanent identity. Her job as an engineer is a fixed characteristic.
Explanation: Use "estar" for location. The cat can move to a different location.
Explanation: Use "estar" for emotions and temporary states. Happiness is a temporary feeling, not a permanent identity.
Explanation: Use "estar" for temporary physical/emotional conditions. Being tired is a temporary state, not a permanent trait.
Explanation: Use "ser" for origin and nationality. Where you're from is a permanent characteristic.
Explanation: Use "estar" with past participles (cerrada) to show the result of an action. Someone closed the door, and it is now in a closed state.
Explanation: Use "ser" for personality traits and permanent characteristics. Intelligence is a fixed quality of who you are.
Explanation: Use "estar" for location. Where someone is located is temporary and can change.