Questions 2 through 5 refer to the following information.
Scientists sometimes group elements according to their properties. Below are descriptions of five physical properties that help identify different elements.
luster—degree to which an element shinesductility—ability to be drawn into wiremalleability—ability to be hammered, rolled, or shapedheat conductivity—ability to transfer heatelectrical conductivity—ability to carry electricity
Questions 6 and 7 refer to the following diagram and information.
Various scientists have proposed models of the atom. The model that is used today is the electron cloud model shown above. In this model an electron moves rapidly through the atom. Its position is described as a cloud rather than a precise point. The outer ring represents the distance from the nucleus where electrons are most likely to be found.
Question 8 refers to the following diagram and information.
Gravity is a force of attraction that exists among all objects. Every object attracts every other object. Most objects are too small for their gravitational force to be measured or even noticed. Because the earth is large, its gravitational force is very strong. Gravity holds things on Earth's surface as it draws everything toward the center of the planet.