Stephanie está haciendo una investigación
con cobre y amoniaco. Ella sumerge el
cobre en una solución de amoniaco. El
cobre cambia a un color azul oscuro.
Stephanie piensa que el cobre se oxida.

¿Qué tipo de cambio ocurre en el cobre
que usa Stephanie?

Acambio físico

B cambio químico

C cambio de estado

D cambio de viscosidad

B Chemical change

Explanation:

Something formed with a dark blue colour. It was a new substance with new properties, so this was a chemical change.

A is wrong because a new substance formed.

C is wrong because the copper stayed solid.

D is wrong because they did not say anything about the viscosity of the solution .

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia