bit 侧重指微小，一点点，小碎片。
piece 最普通用词，多指从整体上分割下来的东西，可大可小。
sheet 侧重指平整很薄的一张或一片。
slice 多指切得很薄的一片食物。
fragment 指破裂的，不完整的，不可完整的碎片。
scrap 侧重指废弃的零碎之物。
参考例句
1. Our boat sliced the lake. 我们小船划破了平静的湖面。
2. Slice the ham thicker. 把火腿片切厚些。
3. Finally, put another slice of bread on the top. 最后，再把另外一片面包放在上面。
英英解释
n.
1. a share of something
2. a serving that has been cut from a larger portion
3. a wound made by cutting
4. a golf shot that curves to the right for a right-handed golfer
5. a thin flat piece cut off of some object
6. a spatula for spreading paint or ink v.
1. make a clean cut through
2. hit a ball and put a spin on it so that it travels in a different direction
3. cut into slices
4. hit a ball so that it causes a backspin
