When scientists say that a theory can never be proven, what are they actually saying? there is no way to test the accuracy of a theory. theories should not be used to make predictions. theories do not need to be tested or challenged. it is always possible for new data to contradict a theory.

Arock can be broken down into different kinds of substances by physical processes. no chemical reactions are needed to separate different parts of a rock into pure substances. this is because a rock is a(n)

Consider three unlabeled bottles, each contain small pieces of one of the following metals. - magnesium - sodium - silver the following reagents are used for identifying the metals. - pure water - a solution of 1.0 molar hcl - a solution of concentrated hno3 (a) which metal can be easily identified because it is much softer than the other two? describe a chemical test that distinguishes this metal from the other two, using only one of the reagents above. write a balanced chemical equation for the reaction that occurs. (b) one of the other two metals reacts readily with the hcl solution. identify the metal and write the balanced chemical equation for the reaction that occurs when this metal is added to the hcl solution. use the table of standard reduction potentials (attached) to account for the fact that this metal reacts with hcl while the other does not. (c) the one remaining metal reacts with the concentrated hno3 solution. write a balanced chemical equation for the reaction that occurs. (d) the solution obtained in (c) is diluted and a few drops of 1 m hcl is added. describe what would be observed. write a balanced chemical equation for the reaction that occurs.

The organism shown is a free-living one that is anchored to the bottom of ponds and streams during one stage of its life cycle what is the common name for the group to which this organism belong