1) Neptunium. In the fall of 2002, a group of scientists at Los Alamos National Laboratory determined that the critical mass of neptunium-273 is about 60 kg. The critical mass of a fissionable material is the minimum amount that must be brought together to start a chain reaction. This element has a density of 19.5 g/cm 3 . What would be the radius of a sphere of this material that has a critical mass?

2) A hydrogen atom has a diameter of 1.06 1010 m as defined by the diameter of the spherical electron cloud around the nucleus. The hydrogen nucleus has a diameter of approximately 2.40 1015 m. (a) For a scale model, represent the diameter of the hydrogen atom by the playing length of an American football field (100 yards= 300 ft) and determine the diameter of the nucleus in millimeters. (b) The atom is how many times larger in volume than its nucleus?

3) Wire is usually sold by pound spools according to the wire gauge number. How many yards are in a 10 pound spool of 12 gauge aluminum wire? 12 gauge wire has a diameter of 0.08008 in. Aluminum has a density of 2.70 g. cm3

4) La masa de un recipiente vac o es de 78.91 g y cuando se llena con agua es de 92.44 g. La densidad del agua es de 1.0000 g/ cm3. Calcule:

a) Calcule el volumen del recipiente.

b) Cuando se llen o con un lquido desconocido, el recipiente tena una masa de 88.42 g. Calcule la densidad del lquido desconocido.

5) Los tomos de cesio de procedencia natural son los de mayor tamao.El radio de un tomo de cesio es de 2.65 ACuntos tomos de cesio tendrn que alinearse uno tras otro para cubrir una longitud de 1.00 in. Considere que los tomos son esfricos.

6) La masa de 1.00 L de leche es de 1.032 kg. La grasa que contiene es de una densidad de 0.865 g/cm3 cuando est a pura, y constituye exactamente el 4 % del volumen de la leche. Cul es la densidad de la leche descremada (sin grasa)?