Conservation of Mass
What is the law of conservation of mass?
The law of conservation of mass states that matter cannot be created or destroyed.
What is a chemical equation?
A chemical equation is a shorthand way to sum up what occurs in a chemical reaction. The general form of a chemical equation is: Reactants → Products.
When is a chemical equation balanced?
A chemical equation is balanced when it has the same number of each type of atom on both sides of the equations.
What chemical reaction is demonstrated in the video?
The chemical reaction demonstrated in the video is the combination of iron (in steel wool) with oxygen (in air) to produce rust, or iron oxide.
Why must all chemical equations be balanced?
All chemical equations must be balanced because matter cannot be created or destroyed in chemical reactions.
Write a chemical equation for the chemical reaction in which calcium carbonate (CaCO3) produces calcium oxide (CaO) and carbon dioxide (CO2).
CaCO3 → CaO + CO2
Balance this chemical equation: CH4 + O2 → CO2 + H2O
The balanced equation is: CH4 + 2O2 → CO2 + 2H2O.
What evidence shows that mass is conserved in the reaction?
The mass of the sealed flask and its contents does not change during the reaction. This shows that mass is conserved in the reaction.
How did Lavoisier demonstrate that mass is conserved in chemical reactions?
Lavoisier demonstrated that mass is conserved in chemical reactions by carrying out many reactions inside a sealed flask. In each case, the mass of the flask and its contents was the same after the reaction as it was before the reaction occurred, showing that mass had not been created or destroyed in the reaction.
Describe in words the chemical reaction represented by the following chemical equation: 2NO2 → 2O2 + N2
Nitrogen dioxide produces oxygen and nitrogen.
1. Which of the following chemical equations is balanced?
a. Zn + HCl → ZnCl2 + H2
b. 2 Zn + 2 HCl → ZnCl2 + H2
c. 2 Zn + HCl → ZnCl2 + H2
d. Zn + 2 HCl → ZnCl2 + H2
d. Zn + 2 HCl → ZnCl2 + H2
How can you tell that oxygen is used up in the reaction?
You can tell that oxygen is used up in the reaction by the movement of the balloon into the flask. With less oxygen in the flask, the pressure of the outside air pushes the balloon inside.
Describe an example of the law of conservation of mass.
When wood burns, it combines with oxygen and changes not only to ashes but also to carbon dioxide and water vapor. The gases float off into the air, leaving behind just the ashes. It may seem as though burning destroys matter, but the same amount, or mass, of matter still exists after a campfire as before. The mass of matter is always the same before and after the changes occur.(OR: Any burning examples explained in detail)
Identify all the parts of a chemical equation.
The parts of a chemical equation include chemical symbols and formulas for reactants and products, an arrow to show the direction in which the reaction proceeds, and plus signs (+) as needed to separate multiple reactants and products. It will also include coefficients and subscripts.
Sam was given the following equation to balance: H2O → H2 + O2. She balanced it as follows: 2 HO → H2 + O2. What did she do wrong? What is the correct way to balance the equation?
Sam changed the subscript for H in H2O from 2 to 1. This is incorrect because changing the subscript changes the substance. It is no longer water. The correct way to balance the equation is to change coefficients: 2H2O → 2H2 + O2.
How can you tell that the product of the reaction is different from the iron that began the reaction?
You can tell that the product of the reaction is different from the iron that began the reaction because it has different properties. The rusted steel wool is brownish red instead of grey, and it is brittle instead of bendable.