Scientific notation is can be very confusing to students. They confuse the positive and negative exponents and when to use them. I have found that by teaching the students to find the old decimal point, label where the new one should go, and count from new to old, it forces them to move in the positive or negative direction, making the sign of the exponent much easier for them to figure out!
Before I move on to percents, order of operations, or even ordering numbers, I like to revisit equivalent rational numbers. I want to make sure that they are comfortable changing numbers into different, equivalent forms.
This is a tic tac toe type chart that can be used to help recall the integer facts for multiplcation. No matter how it is read, it is always correct!
+ x + = +
+ x - = -
- x + = -
- x - = +