The Basics
What does the Law of Conservation of Mass state?
Mass cannot be created or destroyed in a chemical reaction.
When you burn a log, what happens to the total mass of the system?
It stays the same (mass of gases + ash = original log)
What is the purpose of balancing a chemical equation?
To show that mass is conserved
What are the small building blocks of all matter?
Atoms
What do we call the number in front of a chemical formula in an equation?
Coefficient
True or False: The total mass of reactants equals the total mass of products.
True
In a closed container, a metal rusts. Does mass increase, descrease, or stay the same?
It stays the same.
Balance this: H2+O2 -->H2O
2H2+O2 --> 2H2O
They are rearranged, not created or destroyed
What do we call the small number that shows how many atoms are in a molecule?
Subscript
What type of change does the Law of Conservation of Mass apply to?
Chemical and Physical Changes
When you mix vinegar and baking soda in a sealed bag, what happens to the total mass and what is happening?
It stays the same; gas is produced but contained.
Balance this: Na+Cl2 --> NaCl
2Na + Cl2 --> 2NaCl
In a reaction, if there are 6 hydrogen atoms in the reactants, how many should be in the products?
6 hydrogen atoms
In a reaction, 40g of reactants produce 10 g of one product. How much must the other product weigh?
30g
Why is the law important to chemistry?
It helps scientists balance chemical equations and understand reactions.
If a reaction gives off gas and the gas escapes, what seems to happen to the mass?
It appears to decrease, but mass is just lost in the air
Balance this: Fe + O2 --> Fe2O3
4Fe + 3O2 --> 2Fe2O3
What are reactants?
Substances that start a chemical reaction
If you start with 15g of sodium and 10g of chlorine, what's the mass of sodium chloride produced?
25g
Who is credited with discoing the Law of Conservation of Mass?
Antoine Lavoisier
Why is weighing the system before and after opening reaction misleading?
Because gas can escape, making it seem like mass was lost
If an equation isn't balanced, what law is being violated?
The Law of Conservation of Mass
What are products?
Substances formed from a chemical reaction
A closed system reaction starts with 50g of reactants. After there are 10g gas, 30g liquid, and 10g solid. Was mass conserved?