Two students (X and Y) measured the diameter of a gold coin four times. The results were recorded in the table below. The actual diameter
of the coin is 28.0 mm.
a) Which student (x or Y) had measurements that are precise but not
accurate?
b) Which student (X or Y) had measurements precise and accurate?

Explanation:

To solve this problem, we need to understand the concept of precision and accuracy.

Through this understanding we apply to solve this problem.

Precision is the ability to reproduce the same set of values in an experiment. Accuracy is the nearness or closeness of the measured value to the true value.

For example; if the true value is 28.0mm and the following readings were made:

        A  =  24.0mm, 24.0mm, 24.3mm, 23.9mm  This is a precise measurement but not accurate.

      B  =  27.9mm, 28.0mm, 28.1mm:  This is an accurate measurement because it is close to the true value.

Ionic compounds dissociate into component ions dissolved into a solution creating substances called "electrolytes".hope my answer has you : )

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.