I'm not very good at science and this is for a quiz that I'm taking right now. Which is a characteristic of the part of the atom marked "A”?

It contains most of the mass.
It is negatively charged.
It is mostly empty space.
It is composed of electrons.

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=

The amount of heat required to change liquid water to vapor at its boiling temperature is 2256 kj/kg. the amount of heat required to change liquid mercury to its vapor state at its boiling temperature is 295 kj/kg. one kg of each substance is currently at its boiling point. how will the amount of thermal energy required to change each substance from a liquid to a gas differ?

How is density measured? a. area per unit weight b. weight per unit area c. volume per unit mass d. mass per unit volume