If you weigh yourself just before your workout, and then again immediately following your workout (assuming you dried your sweat off) you would see a drop in weight. Most of this would be water weight though. The fraction of your body weight that was actual burnt calories would probably not be detectable by the standard house/gym scale after one workout.

If continue this workout routine and diet and you weigh yourself multiple times a day for many days you will see your weigh fluctuate each day, but the trend across days will be a loss of weight.

That actual caloric burn that will result in the weight loss depends on the type of workout you are doing. Researchers break the type of workouts into three groups. 1) High Intensity, 2) Endurance, 3) High-intensity intermittent

You listed lots of sit-ups or running. Both of these are endurance. This burns carbohydrates (sugars) as fuel first. This means the sugars in your blood from what you ate first, then the sugars stored up in your muscles, then the sugars synthesized by your liver.

The more intense you workout, the more your body will rely on sugars, and turn off the mechanisms that burn stored fat.

As the time (duration) of your workout increases, your body will switch to burning fat. Typically you have to workout for 90 minutes before your body really begins to burn fat for your workout.

Its also important to keep in mind that if you drink sugary sports drinks during your workout, they too turn off your body's fat burning mechanisms in favor of carbohydrate burning ones.

After your workout your body will continue to burn calories at an accelerated rate for as long as your body temperature is elevated, and as long as it takes to replenish the metabolic stores in your muscles.