The bond angle of bonds in an octahedral molecule is 90 degrees
The formula for density is D=m/v, where m=mass and v=volume. So we can just do 890/100 and we end up with 8.90. The density of the copper is 8.90 grams per cm3
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The circumstances when scientists use observational research and opinion based research is when they include animals or things that cannot control for a product. Observational research is a type of research which only observes ongoing behavior and studies about it and the results only rely on the behavior observed.