Put your hand up if you like to lift weights, now pat yourself on the back!
Put your hand up if you like lifting heavy weights, now give yourself a round of applause!
Put your hand up if you bounce the barbell off your chest when you chest press, hang your head in shame!
Bouncing the bar is poor form, poor form will prevent your muscles getting the best workout, will cause injury and will stop you from getting big gains!
During bicep curls, the same practice can be seen but instead of bouncing, it is swinging. Have you ever seen someone swing the barbell or dumbell in order to complete the rep?
As a general rule, if your heel lifts off the ground, you are attempting too much weight.
If you focus on the right form, the right technique and lift the right amount of weight, you will see solid gains and avoid injury. Search on YouTube for proper lifting techniques, trust me it is worth it. Utilise the preacher bench, again you will be thanking me.
Good luck and lift heavy (safely)!