Chá de bebê
It is a 'baby shower', a party for a women who is going to have a baby. Her friends take presents for the new baby. The plural is chás-de-bebê.
Chá de panela
Chá de panela ís party for a woman who will soon be getting married. Guests, usually only women, are expected to take presents for the kitchen or the home generally.
dar um chá de sumiço
The expression means to disappear.
Chá de cadeira
This phrase was originally used to refer to girls at a ball had to wait a long time to be invited to dance and had to patiently sit in the chair drinking tea. Nowadays, it is used for any long wait. The plural is chás-de-cadeira.