A:科学假说
B:理想模型
C:等效替代
D:控制变量
Cu+2H2SO4(浓) CuSO4+SO2↑+2H2O
有人设计了用铜屑制取CuSO4的两种方案:
①Cu →Δ浓H2SO4 CuSO4
②Cu →Δ CuO →稀H2SO4 CuSO4
从节约原料和保护环境的角度考虑,较好的方案是( )
28mm+58mm=____mm ____m+37m=60m
90mm-35mm=____mm 50m-____=5m
We will have to choose a person to __________ our class to take part in the competition.