It really depends on the manufacturer as to what "baby weight" yarn means. The Craft Yarn Council of America is attempting to set standards as to yarn weigh, but there isn't a requirement for manufacturers to follow their guidelines.
According to CYCA, a "baby weight" yarn should be 27-32 knit stitches per four inches. All yarn "weights" generally are based upon how many stitches there are in 4 inches.
If you are attempting to follow a pattern, check and see how many stitches are in four inches of the gauge swatch. Use this information to go shopping for that weight of yarn.
Ir shouldn't as long as it is made by the same company and it is the same weight. Worsted weight will be thicker than Baby Sport or Baby Soft.
It will depend on the type of yarn. 225 yards of worsted weight yarn is about 100g, but 225 yards of sock weight yarn is about 25g. What is the yarn type?
In the UK, worsted weight yarn corresponds to 10ply (i.e. heavy DK or light aran yarn)
There are several places where you can purchase bulky baby yarn. Hobby Lobby and Jo-Ann Fabric & Crafts usually carries bulky baby yarn in most stores. Online the yarn can be bought at Yarn Supply and Amazon.
Your answer depends on the weight of the yarn.Thread weight yarn will weigh less than bulky weight, given 'five balls' of each.
It appears that there is no readily available answer to this specific yarn (Unger's Roxanne). The reason is that Unger's went out of business, got bought out by another company, or another reason. One way to figure out what the yarn weight of a ball of yarn would be to knit a stockinette gauge swatch, (or a crochet gauge swatch), then by counting the stitches, for four inches, and dividing by 4, you get an average stitches per inch. From there find your yarn weight at the Yarn Council recommended standards to get a guess at the yarn weight, ---Otherwise, take the yarn to your local yarn shop and see what weight they guesstimate for you <--this is probably your best bet at finding your yarn weight and information, btw
Your answer depends on the weight of the yarn -- thread weight yarn weighing a total of 100 grams will contain more yardage than a bulky weight yarn ball weighing 100 grams.
Depends on the material of the yarn, diameter, etc.
You can learn more about yarn weights, below.
Most 4-ply yarns are medium-weight, which may carry the name worsted weight yarn. Ply is a complicated thing. Thickness and ply of yarn is different depending on where the yarn is manufactured. In the U.S. worsted weight is generally 4 ply. The number of plies is not always an indication of weight, however. It is just tells you how many strands are used in that type of yarn.
4ply is NOT a yarn weight. Many 4ply yarns in the US are worsted weight. DK is a lighter yarn weight.
It can vary greatly depending on your yarn tension and the size of the hook you are using. The more tension and the smaller the hook, the more yarn it will take. It also depends upon the type of yarn you are using. Thinner yarn (such as baby yarn or sport weight yarn) will require more yards to complete 1 square foot. Thicker yarn will require less yards to complete 1 square foot.