If a sample is packed poorly, the sample will not heat evenly and will take longer to melt.
Nonpolar covalent bonds are chemical bonds where two atoms share a pair of electrons with each other and the electronegativities of the two atoms are equal. An example is methane. It has four carbon-hydrogen single covalent bonds. These bonds are nonpolar because the electrons are shared equally.
Yup go this website for more information http://dwb.unl.edu/calculators/activities/BalEqn.html
We have as a reagent a salt, lead nitrate (Pb(NO3)2), and an unknown solution that gives us as a product lead chloride (PbCl2). That is, the solution must contain chlorine.
If a chlorine solution is used we will have the following reaction:

So, with a chlorine solution, we will have a white precipitate of lead chloride.
The scientific method is defined as a method of research in which a problem is identified, relevant data is gathered, a hypothesis is formulated from this data, and the hypothesis is empirically tested.