Working to fast through repetitions and using momentum instead of muscle power will result in less muscle building and calorie burning. You'll also be increasing your risk of serious injuries such as torn muscles or connective tissue.
You can easily fix this if you take about 5 seconds for each repetition: 2 seconds to lift the weight and 3 seconds to lower the weight. On the negative phase of the repetition (when you are lowering the weight) it is very important to fight against gravity so that you give your muscles a sufficient challenge.
Try this the next time you workout. Remember slow and controlled movements are the key for impressive results from strength training.