Physical & Chemical Changes
Nails rusting, Wood burning, and Baking a cake all indicate what type of change?
Chemical Change
In an ionic bond, valence electrons are.....
2HCl + Br2 ---> 2HBr + Cl2
Compound Initial Mass (g) Final Mass (g)
HCl 25 0
Br2 10 0
HBr 0 2
Cl2 0 ?
33 g
Identify the products in this chemical equation
2HCl + Br₂ → 2HBr + Cl₂
2HBr & Cl₂
Atoms bond to gain, lose, or share electrons during chemical changes in order to become
chemically stable
In a lab, you put vinegar in a flask and baking soda in a balloon. Once you lifted the balloon up and the baking soda mixed with the vinegar, the balloon inflated. What type of change occurred?
A chemical reaction (change) occurred between the vinegar and baking soda, creating a gas.
Ionic bonds occur between a _____________ and __________
metal & a nonmetal
An exothermic reaction occurs when the amount of energy required to break the bonds to start the reaction is _______________ than the amount of energy _______________.
less; released
Balance the following equation (SHOW YOUR WORK)
____MgAr + ____PdI2 → ____MgI + ____PdAr2
2MgAr + 1PdI2 → 2MgI + 1PdAr2
Dissolving is an example of what kind of change?
Physical
Salt dissolving, Ice melting, and tearing paper all indicate what type of change?
Physical Change
In a covalent bond valence electrons are.....
shared
The initial temperature of a substance was 30 degrees C. It's final temperature, after the reaction occurred was 80 degrees C. Is this an example of an endothermic or exothermic reaction?
Exothermic. Temp went up
The _______________ _______________ _______________ says that matter can be neither created nor destroyed.
Law of Conservation of Matter
In a bond formed between Carbon and Oxygen, which statement describes what happens to the electrons?
a. Carbon shares two electrons with oxygen to form an ionic bond.
b. Carbon transfers two electrons to oxygen to form an ionic bond.
c. Carbon transfers two electrons to oxygen to form a covalent bond.
d. Carbon shares two electrons with oxygen to form a covalent bond.
d. Carbon shares two electrons with oxygen to form a covalent bond.
Identify which would be a physical change
- Crushing a solid
- Shape Change
- Temperature Change
- Phase Change
- Bubbles Form
- Crushing a solid
- Shape Change
- Phase Change
Covalent bonds occur between 2 ____________
nonmetals
Heat is absorbed and makes things colder in this type of reaction
Endothermic
Identify the reactants in this chemical equation
3H₂ + N₂ → 2 NH₃
3H₂ & N₂
Which takes place when a chemical change occurs?
A. Bonds connecting atoms in products break, and reactants form
B. Bonds connecting atoms in products break, and reactants break
C. Bonds connecting atoms in reactants break, and bonds connecting atoms in products
form
D. Bonds connecting atoms in reactants form, and bonds connecting atoms in products
break
C. Bonds connecting atoms in reactants break, and bonds connecting atoms in products
form
Remember: We start with reactants and end with products. You have to break the reactants apart before you can build the product, just like you have to break apart LEGOS first before you can build something new with them.
Identify which would be a chemical change
- Ice Melting
- Cooking Food
- Temperature Change
- A gas is produced
- Chopping Wood
- Cooking Food
- Temperature Change
- A gas is produced
Determine which of the following compounds are examples of ionic or covalent bonds
1. LiCl: Transfer or Share?
2. KS: Transfer or Share?
3. ArB: Transfer or Share?
4. KrO: Transfer or Share?
1. LiCl: Ionic; Transfer
2. KS: Ionic; Transfer
3. ArB: Covalent; Share
4. KrO: Covalent; Share
Determine which of the following is an example of the most endothermic reaction.
Compound Initial Temp. Final Temp
1 25 10
2 10 25
3 50 40
4 0 100
5 25 5
Compound 5 because it has the biggest temp change
Balance the following equation (SHOW YOUR WORK)
___Na + ___O₂ → ___NaO₂
2Na + 2O₂ → 2NaO₂
Which of the chemicals below could be the identity of a substance that shares electrons and is a poor conductor of heat and electricity?
a. H₂O
b. CaF₂
c. MgO
H₂O