Copper is a heavy metal that can harm many people. This process of heavy metals building in your body is called bioaccumulation and the process of this building in the food chain is called biomagnification. Its hard to rid of this heavy metal because it is very dense, therefore, cannot breakdown in our bodies. Heavy metals get consumed by producers and then reach to the top of the pyramid (us) so we have the highest risk of getting diseases and so on. Make sure you explain that heavy metals get passed from industrial purposes where companies do not dispose of waste properly.
Source: Exam as well
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Yes. Everything is made up of mass. If it takes up space, it has mass
Answer: The ratio of carbon dioxide molecules to oxygen molecules is 20 :31
Explanation:
Combustion is a chemical reaction in which hydrocarbons are burnt in the presence of oxygen to give carbon dioxide and water.
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
The balanced combustion reaction is,:

Thus the ratio of carbon dioxide molecules to oxygen molecules is 20 : 31