Chapter U1, Problem C2.2RE

Interpretation Introduction

Interpretation:

Law of conservation of massand how it relates to the copper cycle haveto be explained.

Concept introduction:

Sometimes matter is changed into new physical forms and sometimes it is changed into a new substance. Some changes are temporary while some changes are permanent. In a copper cycle, several chemical reactions are done. The cycle starts with copper and ends with copper. Copper is made to react with acids, a base and a metal at different stages. Several intermediate products are formed and a gas is also produced. The cycle involves five different steps and in each step a new substance is formed.

Answer to Problem C2.2RE

The law of conservation of massstates that mass cannot be gained or lost in a chemical reaction. In other words, matter cannot be created or destroyed.

If the mass of copper powder is measured at the start and end of the copper cycle experiment, one can find that no copper was gained or lost during the cycle. If an experiment is done perfectly, one would get the exact amount of copper as in starting. There might be some loss of copper due to human error. Nevertheless, total mass is still conserved.

Explanation of Solution

Given information:

In the copper cycle experiment law of conservation of mass is followed.

The law of conservation of massstates that mass cannot be gained or lost in a chemical reaction. In other words, matter cannot be created or destroyed.

The copper cycle experiment shows that many different products are formed as copper is treated with different acids, a base and a metal. The cycle is a full circle as it brings back the element copper with which the cycle starts. After several steps, copper is obtained again. Whatever treatment is done on copper, there is copper always present in some form in the new products. It is neither created nor destroyed through chemical transformations. Even if it is considered that some amount of copper is lost in the experiment due to errors in measurement, because of spills and some sticking on the paper and beaker; total mass of copper remained same.

Total mass of copper remained same at the end of the experiment which proved that law of conservation of mass is followed.

Hence, one can say that during chemical changes the elements are neither created nor destroyed. They are always present in the new compounds that are formed. There is a conservation of mass of elements in a chemical change.

Conclusion

During chemical changes the elements are neither created nor destroyed. They are always present in the new compounds that are formed. There is a conservation of mass of elements in a chemical change. Law of conservation of mass is followed by elements during a chemical change.