What are the evidences of chemical decomposition?

we conducted an experiment on the chemical decomposition of sodium bicarbonate. first, we heated 1.0 g of sodium bicarbonate inside a beaker for 15 minutes. the weight decreased after heating. why did it happen? and in the 2nd set-up, we heated a 1.0 g of sodium bicarbonate inside a test tube with a stopper tubing leading to test tube that contains a saturated solution of calcium hydroxide. during heating, water droplets appeared in the test tube. bubbles are formed inside the beaker and there are white solid particles that are formed at the bottom of the beaker. what is the white solid material? is it sodium hydroxide, sodium carbonate, or sodium oxide? and what can be a chemical test to determine the solid material? thankyou!!!