Identify the following statements as True or False?

1. Copper has a higher thermal conductivity than aluminum.

2. The density of copper is closer to that of aluminum than it is to iron.

3. Bronze alloys with more than 20 wt% tin are quite ductile and easily cold-worked compared to alloys with 5 wt% tin or less, because large additions of the soft metal tin enhance the ductility of copper.

4. Copper and its alloys form a green tarnish over time, consisting of sulfides and carbonates.

5. The electrical conductivity of somewhat impure copper alloys can actually be increased by introducing a small amount of oxygen into the copper, provided the oxygen reacts with impurities and coalesces them into larger oxide particles.

6. Copper is relatively resistant to corrosion by neutral and even mildly basic water.

1. False

2. True

3. True

4. True

5. True

6. True

1. True

2. False

3. False

4. True

5. False

6. False

Explanation:

1. True.

Thermal conductivity of copper : 385.0 W/m K; Thermal conductivity of aluminium : 205.0 W/m K. Cu has higher thermal conductivity than Al

2. False

Density of Copper: 8.96 g/cm3; Density of Iron: 7.87g/cm3; Density of Iron: 2.70/cm3. The density of copper is closer to that of aluminum than it is to iron.

3. False.

This is true because thin is a ductile material and alloys with more Tin are more ductile than alloys with less tin.

4. True

copper that is exposed to the elements undergoes a series of chemical reactions that give the shiny metal a pale green outer layer called a patina.

5. False.

The electrical conductivity of copper can not be improved by oxygen. In fact, the formation of oxides reduces the electrical conductivity.

6. False.

Copper easily oxidizes when exposed to moisture from water to form a tarnished surface.