This lab question is: how can you distinguish a physical change from a chemical change?

which statements below are an appropriate hypothesis in response to this question? check all that apply.

if a substance changes state of matter (e. g., liquid to gas), then this is a physical change because the original properties of the substance have not changed.

if a substance undergoes a physical change, then it will retain most of its original properties because no new substance is formed.

if a substance undergoes a chemical change, then it will not retain its original properties because a new substance is formed.

if a precipitate is formed when two substances are mixed, then a chemical change has taken place because precipitates are new substances.

a basic solution is an aqueous solution containing more oh-ions than h+ions. in other words, it is an aqueous solution with a ph greater than 7. basic solutions contain ions, conduct electricity, turn red litmus paper blue, and feel slippery to the touch.

explanation:

the awnser is group 12

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol