What happens in a Chemical Reaction?
- Chemical ___________ in the reactants are _____________, then atoms are ____________ to form new substances (______________).
- The amount of ____________ does not ____________ during a chemical reaction, the __________ are only rearranged to form _______ substances.
- This is evidenced (____________) in a balanced chemical _________________
What is a Chemical Equation?
- A chemical equation is a way that scientists ________________ a chemical ____________ that has occurred. It shows the __________________ of atoms in a chemical reaction.
- It contains the chemical ____________ of the substances involved in the reaction.
- An ___________ is used to distinguish between the reactants and ____________, and can be understood as meaning “__________” or “___________”.
- _______________ are the substances broken apart or combined in a chemical reaction (what you ___________ with!) and they are located on the _______ side of the arrow in a chemical ______________.
- _______________ are new substances formed in a chemical reaction (what you _________ with!) and they are located on the ___________ side of the arrow in a chemical ________________.
- Ex: C + O2 → CO2
- This equation says “carbon __________ with oxygen to _____________ (make) carbon dioxide.”
- The arrow shows the ________________ of the reaction:
- _____________ → _______________
What is the Law of Conservation of Mass?
- When substances ___________ with each other, many ________________ can take place, but in every case the total amount of __________ afterward is the _________ as before.
- Discovered by Lavoisier—_____________ chemist
- Law of Conservation of _________: in a chemical rxn, _________ (________) is neither ___________________ nor ___________________
- Mass of = mass of products
- All ____________ present in the reactants are also present in the _____________. There must be the ___________________ of atoms in the products and reactants.
Mass Stays the SAME
- The __________ of the products must be the __________ as the mass of the ___________
- You do not magically gain or lose mass!!!
- Example: If you have ____ grams of Na react with ____ gram of Cl to make NaCl, you know you must have ____ grams of NaCl in the products!
__ g + __g → ___g
Number of Atoms Stays the SAME
- You must have the _________ number of atoms of _______________________ on both sides of the equation.
- If you have ____ atoms of oxygen in the reactants, you must have ____ atoms of oxygen in the products. (You do not magically gain or lose atoms!!!)
- This is NOT something someone made up; it’s how chemical reactions happen in ____________!
How can I tell how many atoms of each element there are?
- Coefficient: the “_________” number written in ___________ of a chemical ___________ that tells you how many _________________ of that substance there are.
- Ex: 5 H2O = ____ molecules of water
- The _________________ tells you how many ___________ of each element there are.
- The coefficient __________ the subscript tells you how many _________________ of that element are present.
- 5 H2O = ____ atoms of Hydrogen, ____ atoms of Oxygen
- If there is _____ coefficient, then there is only _______ molecule of that substance!
What does it mean to Balance a Chemical Equation?
- Sometimes we have to “______________” a chemical equation to make sure that we have the ___________ number of ___________ of each element on ___________ sides of the equation. To do this, we change the number of _________________ by changing the ___________________ (NEVER THE _____________________!!!) until we have the same number of atoms of each ______________ on both sides. When we do this, we are saying how many _______________ of each substance must be ______________ before the reaction will _____________________ (remember: this is not something scientists made up; this is how the reactions happen in ____________!).
How do I know if a Chemical Equation is Balanced?
- Check the number of _____________ of each element on both sides of the equation (reactants and products).
- If the number of atoms of each element is the _________________ on both sides, then the equation is balanced.
H2 + O2 → H2O : _______________________________
2H2 + O2 → 2H2O : _____________________________