Mining for copper and iron

1. The difference is whether carbon dioxide is involved

the condition needed for copper to rust is actually the result of the interaction between copper and oxygen, water and carbon dioxide
the chemical equation of copper rust: 2Cu + H2O + CO2 + O2 = Cu2 (OH) 2CO3
iron rust is the result of the interaction of iron and oxygen water
the chemical equation of iron rusting: 2Fe + 3O2 = 2fe2o3

2. (1) Because V Cu = V Fe, m Cu / M Fe= ρ Copper/ ρ Fe = 8.9 / 7.9 ≈ 1.13
(2) because m Cu = m Fe ρ Copper V copper= ρ Fe V Fe
V Cu / V Fe= ρ Iron/ ρ Copper = 7.9 / 8.9 ≈ 0.89
(3) copper must be hollow
If copper is solid, ρ Copper is greater than ρ If the volume of iron is the same, m copper must be larger than m iron

3. B

4. Copper bar

6. C
because of C copper < C iron < C aluminum, the aluminum block needs to absorb the most heat when heating up.
assuming the final temperature T, then
(T-30) * m * C = (100-t) * m * C, where m and C represent metal, m and C represent water
so t = 30 + 70mc / (MC + MC)
so the larger C is, the smaller t is

7. Because two pieces of copper and three pieces of iron weigh 360 grams, that is, four pieces of copper and six pieces of iron weigh 720 grams, and four pieces of copper and five pieces of iron weigh 660 grams, one piece of iron weighs 720-660 260 grams, that is, one piece of copper weighs (360-3x60) / 2290 grams

8. When compressed, the iron atoms and copper atoms are closely connected and close together

9. There is no absolute sense of good or bad
in dynamic balancing, if there is too much weight shortage, the fan-shaped surface of the balance weight (iron) will be too large, thus recing the equivalent weight of the balance weight. In this case, it is recommended to use copper balance weight (the proportion of copper is greater than that of iron). Therefore, in general, try to use iron balance weight, after all, cheap.