Give an example of a physical process that illustrate the law of conversation of mass?

Answer 1

All physical processes obey the law of conservation of mass. This law is only broken in nuclear reactions. Thus, one example of this law is breaking glass. The mass of the glass before being broken is the same as its mass after its broken.

The lab in the Modern Chemistry textbook shows the law of conservation of mass before and after combining vinegar and baking soda. This is a chemical process.

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Chapter 3 Review- Atoms: The Building Blocks of Matter

(pages 17/18 in 2011 workbook)

Here are all the questions and their corresponding answers:

1. Why is Democritus's view of matter considered only an idea, while Dalton's view is considered a theory?
   • Democritus's idea of matter does not relate atoms to a measurable property, while Dalton's theory can be tested through quantitative experimentation.
2. Give an example of a chemical or physical process that illustrates the law of conservation of mass.
   • A glass of ice cubes will have the same mass when the ice has completely melted into liquid water, even though its volume will change. (Accept any reasonable process.)
3. State two principles from Dalton's atomic theory that have been revised as new information has become available.
   • Atoms are divisible into smaller particles called subatomic particles. A given element can have atoms with different masses, called isotopes.
4. The formation of water according to the equation...

   2H2 + O2 → 2H2O

   ...shows that 2 molecules (made of 4 atoms) of hydrogen and 1 molecule (made of 2 atoms) of oxygen produce 2 molecules of water. The total mass of the product, water, is equal to the sum of the masses of each of the reactants, hydrogen and oxygen. What parts of Dalton's atomic theory are illustrated by this reaction? What law does this reaction illustrate?

   • Atoms cannot be subdivided, created, or destroyed. Also, atoms of different elements combine in simple, whole-number ratios to form compounds. The reaction also illustrates the law of conservation of mass.
5. If 3 g of element C combine with 8 g of element D to form compound CD, how many grams of D are needed to form compound CD2?
   • 16g
6. A sample of baking soda, NaHCO3, always contains 27.37% by mass of sodium, 1.20% of hydrogen, 14.30% of carbon, and 57.14% of oxygen.

   a) Which law do these data illustrate?

   • the law of definite proportions
   b) State the law.
   • A chemical compound contains the same elements in exactly the same proportions by mass regardless of the sample or the source of the compound.
7. Nitrogen and oxygen combine to form several compounds, as shown by the following table.

   a) 2.0

   b) 2.0 (really 1.9) (based on my calculations)

   c) 4.0 (really 4.9) (based on my calculations)

   d) law of multiple proportions

For the last ones, (#7) replace the "NO#" etc letters with the numbers in the chart and divide.

All of these answers come right from the answer book!

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