Lifting Question....

It depends entirely on your ability.

Think of it this way, if you can not do more than 6 reps (my opinion) with a given weight;then its heavy.

10 lbs may be heavy for one, 50lbs may be light for another.

"Heavy" lifting is for build/bulking up muscles. So the real question is do you want to increase your muscles mass or tone it up and are looking for more definitiion. IF you want to bulk up I would suggest going a little heavier maye 15 or 20 pounds. The next questions is can you do the 10 pounds with relative ease. If you are blowing through your reps at 10 pounds and want to tone up that is fine, if you want to bulkl up you need to do a heavier weight with less reps.

I have to disagree with you regarding women bulking up using heavier weights. Women can't bulk up like men can. Often times women don't lift heavier because of this misconception.

Generally you base on what kind of lifting you do by the amount of repetitions you do. Lower the reps... heavier weight should be done, and if your lifting lighter (cutting) you should have lighter weight/more reps.

For instance - When doing dead lifts or bench press, if I'm going for muscle gain i'll do 8 reps maximum, my last rep or 2 are typically to failure. That is "heavy" lifting _FOR_ me. Some guys I've worked out with do strictly 5 sets of 5 reps, using straps to eliminate grip issues, and lift as heavy as they can for those 5 reps.

It's not about bulking up or not, forget about that.
It is nearly IMPOSSIBLE for someone to ADD muscle while in a calorie deficit. What you are trying to do is strengthen your existing muscle fibers and protect the muscle you DO have from being destroyed by eating too little.
Furthermore, women have an EXTREMELY hard time "bulking up" without steroids. You will not look like a bodybuilder no matter how heavy you go.

That being said:
"Heavy" is the amount of weight that you can do 10-12 reps with, knowing that you probably could NOT do the 13th. That 12th should be a real struggle. This could be any weight, it varies person to person and exercise to exercise.
I would suggest not wasting your money on 3 lb or 5 lb dumbells as they are useless. I am 5'2" 107 lbs and I use anywhere from 10 to 30 for handhelds depending on the exercise.

here my take, this is what i have found works for me, i do reps of 12-15 and do 3 sets with a minute to a minute and a half of rest between, lets use my tricep pull down as an example. i do my first set with 40 pounds, i do my second set with 45 pounds, and my final set is 50 pounds, the point is to start with your comfort weight, add a little more, and then add a little more than that. the point is to tear or shred the muscle as you use it, so that it heals and gets stronger and burns more fat. using the muscle is one thing but pushing it to the absolute max and actually damaging it is where the benefit comes in.

It's not about bulking up or not, forget about that.
It is nearly IMPOSSIBLE for someone to ADD muscle while in a calorie deficit. What you are trying to do is strengthen your existing muscle fibers and protect the muscle you DO have from being destroyed by eating too little.
Furthermore, women have an EXTREMELY hard time "bulking up" without steroids. You will not look like a bodybuilder no matter how heavy you go.

That being said:
"Heavy" is the amount of weight that you can do 10-12 reps with, knowing that you probably could NOT do the 13th. That 12th should be a real struggle. This could be any weight, it varies person to person and exercise to exercise.
I would suggest not wasting your money on 3 lb or 5 lb dumbells as they are useless. I am 5'2" 107 lbs and I use anywhere from 10 to 30 for handhelds depending on the exercise.

You surely can gain muscle when you are in a caloric deficit as long as you keep a high level of protein in the body.

Heavy is training to failure, where your muscle cannot complete another rep, on at least one set.. Now, just how much weight it takes to achieve that result depends on the movement being done and the lifter's relative strength level. A compound movement like the squat or bench press, which utilize multiple muscles during the movement, can be done with more weight than an isolation exercise, such as the biceps curl, which utilizes fewer muscles.

There's also a myth that higher reps with lighter weight will help you achieve a "toned" look. This is a fallacy based on the fact that any exercise for which you can complete 20 reps or more is not putting your body into an anabolic state, but rather an aerobic one. In other words, you're doing a different form of cardio, not working hard enough to break down the muscle tissue in order to promote growth.

As for reps, 8-12 per set has been found to be ideal to promote growth of lean mass. You should be working with enough weight to reach failure on at least your final set. 4-6 reps is ideally suited to increase overall strength, but working in the 6-10 and 12-15 rep range can also be beneficial as well, particularly for breaking out of a plateau.