Which is the best explanation of his results? The heating changed some of the sample to gas, causing the mass to decrease without breaking down the
sample. Therefore, the original sample is a compound.
The appearance stayed the same, showing that the sample was not broken down by heating. Therefore, the
original substance is an element.
O The mass decreased during heating and some of the impurities escaped. Therefore, the original substance is
an element.
The chemical reaction with acid changed, showing that the sample was broken down by heating. Therefore, t
original substance is a compound.

The mass decreased during heating and some of the impurities escaped. Therefore, the original is an element

a small object of mass 3.66 g and charge -17.6 µc is suspended motionless above the ground when immersed in a uniform electric field perpendicular to the ground. what are the magnitude and direction of the electric field?

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )