Experiment of to prove the law of conservation of mass
Answers
Answer:
General Objective: Students create their own experiment to prove the Law of Conservation of
Mass after conducting a guided practice lab.
Instructional Goals:
1. Given vinegar and baking soda along with specific directions, students prove the Law of
Conservation of Mass.
2. Given Alka-Seltzer and a flask, students design and conduct an experiment to prove the
Law of Conservation of Mass.
The law of conservation of mass indicates that mass cannot be created nor destroyed. This
means the total mass of reactants in a chemical reaction will equal the total mass of the
products. If a gas is produced during a reaction, which mass is often forgotten when
calculating the final mass because the students are unable to see the gas. For this reason,
balloons or zip lock bags may be used to collect the gas and preserve the mass.
When balancing chemical equations, the law of conservation of mass is also demonstrated
because the total number of atoms that goes into the reaction must be produced. So if 14
atoms are on the reactant side, then 14 atoms must be on the product side. Equations often
require balancing to correctly demonstrate the law of conservation of mass.
Students work in small cooperative groups to complete a laboratory exercise related to
conservation of mass. Using vinegar, baking soda and a sealed plastic bag, students
determine the mass of the vinegar and baking soda. Students then seal the vinegar and
baking soda in a plastic bag and mix the substances. A gas is formed which will inflate the
bag. The mass of the sealed bag will then be determined in order to ascertain if there has
been any change in the mass of the reactants and product before and after the reaction took
place.
In the second activity, students design their own investigation to observe and prove the law of
conservation of mass. The first investigation should provide them with the knowledge they
need a closed system so the mass of the gas is included. Depending on the restrictions you
provide, this activity could use a large number of seltzer tablets. Consider restricting their
supply to 2 or 3 tablets, depending on your supplies. Allow students to ask you for additional
supplies they might need. Ensure students have a plan in writing before they start testing.
We have long known that atoms can be neither created nor destroyed during a chemical
reaction. The number of atoms of each element must be the same before and after the
chemical reaction.
If the number of atoms of each element remains the same, then the mass can never change
in a chemical reaction. The total mass of the reactants must equal the total mass of the
products. This observation that mass must remain constant in a chemical reaction as known as law of conservation of mass
According to the law of conservation of mass, during any physical or chemical change, the matter is neither created nor destroyed. However, it may change from one form to another. Below, we have listed an experiment that will help you verify the law of conservation of mass.
Requirements: H-shaped tube, also known as Landolt’s tube; Sodium chloride solution; silver nitrate solution.
Procedure: Sodium chloride solution is taken in one limb of the H-tube and silver nitrate solution in the other limb as shown in the figure. Both the limbs are now sealed and weighed. Now the tubes are averted so that the solutions can mix up together and react chemically. The reaction takes place and a white precipitate of silver chloride is obtained. The tube is weighed after the reaction has taken place. The mass of the tube is found to be exactly the same as the mass obtained before inverting the tube. This experiment clearly verifies the law of conservation of mass.