Identify the variables in the investigation: An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different size nails were used. The number of paper clips the electromagnet could pick up was measured.

Independent: sizes of nails

Dependent: number of paper clips

Controlled: Battery, wire and type of nails

Explanation:

An independent variable is a variable which when changes does not the effect the results of the experiment. It does not depends upon the dependent variable.

A dependent variable is defined as a variable which is affected when the independent variable is changed by the researcher or the experimenter. It depends greatly upon the independent variable.

While a controlled variable is that variable whose value is not changed in an experiment. It contains all the constants.

In the context,

the independent variable are : sizes of nails

the dependent variables are : number of paper clips

the Controlled variables are: Battery, wire and type of nails

hope this

explanation:

covalent bonds

consist of pairs of electrons shared by two atoms, and bind the atoms to fixed orientation and requre high energies to break them

ionic bonds

when two atoms differ considerably in their electronegativity, then one of the atoms will lose its electron to the other atom. this results in a positively charged ion(cation) and a negatively charged ion (anion)