Question

Use the equation and the information in the table to answer the question.

CH4 + 2 O2 → CO2 + 2 H2O

Atomic Mass (amu) of Hydrogen, Carbon, and Oxygen
Element Atomic Mass (amu)
hydrogen 1
carbon 12
oxygen 16
In one to two sentences, explain two different ways the equation demonstrates the conservation of mass.

(2 points)

Short Answer Rubric (2 points)
Points Awarded Criteria
2
The answer is very clear.

The answer is fully supported by details.

There may be a few errors in grammar, usage, or mechanics. Errors do not interfere with meaning.

1
The answer is somewhat clear.

Details are weak or not related.

There are some errors in grammar, usage, and mechanics. Errors interfere with meaning.

0
The question is not answered.

Answer 1

1) By counting atoms: both sides have 1 C, 4 H, and 4 O (CH4 + 2 O2 → CO2 + 2 H2O), so no atoms are lost or gained. 2) By mass using the atomic masses: CH4 = 12 + 4(1) = 16 amu, 2 O2 = 2(2·16) = 64 amu, total reactants = 80 amu; CO2 = 12 + 2·16 = 44 amu, 2 H2O = 2(2·1 + 16) = 36 amu, total products = 80 amu, so mass is conserved.