What Are Chemical Equations?
Chemical equations show the products that the combination of reactants yield, but the equation doesn’t show how the reactants form those products. What we don’t see are the underlying chemical and physical changes that allow molecules to rearrange to change properties or create new substances.
Chemical Changes
Generally, chemical changes involve intramolecular (literally meaning “inside molecule”) bonds. This includes breaking and/or forming bonds between elements. Let’s look at a chemical reaction using Lewis Dot Diagrams to visualize it.
The synthesis reaction above shows an interaction between magnesium and oxygen. The bonds that are broken are red, and the bonds formed are green. Here, we can see that the oxygen’s covalent bonds had to break, and then new ionic bonds formed between the magnesium and oxygen.
Physical Changes
Physical changes are usually intermolecular changes (literally meaning “between molecules”), such as phase changes. Some examples are freezing water🧊 and cutting paper✂️📄.
The ice’s molecules maintain the same atomic structure (H2O), but more hydrogen bonds between each water molecule are formed. Conversely, the paper’s molecules keep the same atomic structure, but the interaction between the paper molecules are broken.
However, some reactions can go either way. For example, the reaction between salt and water involves breaking the bonds between ions, but it also creates ion-dipole interactions between the water and ions.
Review Activity
Name whether each scenario describes a chemical or physical change.
Burning a match🔥
Iron rusting over time🚲
Mixing two powders🥣
Answers
Burning a match is a chemical change
Iron rusting is a chemical change
Mixing two powders is a physical change
🎥 Watch: AP Chemistry - Physical and Chemical Changes (Intro to Chemical Reactions)
Get your ap chem survival pack!
Download our ap chem survival pack and get access to every resource you need to get a 5.
ap chem
✍️ Free Response Questions
AP Chemistry Free Response Questions
- Overview of AP Chemistry FRQs
- Exam Format
- How to Ace the FRQ - Step by Step
- AP Chemistry FRQ Tips
- Concise and Clear is Key
- Stay Consistent
- Cash In On Credit
- Words and Symbols
- Know Your Chemistry
- Example FRQ - Short Answer (4 points)
- Break Down
- Scoring Guidelines
- Example FRQ - Long Answer (10 points)
- Break Down
- Scoring Guidelines
⚛️ Unit 1: Atomic Structure and Properties
🤓 Unit 2: Molecular and Ionic Compound Structures and Properties
🌀 Unit 3: Intermolecular Forces and Properties
3.6Deviations from the Ideal Gas Law
- When Do Gases Deviate From The Ideal Gas Law?
- Gas particles can become attracted to each other➡️⬅️
- Gas particles can make up a significant portion of a gas samples’ volume
- Graphically
- Correcting the Ideal Gas Law using the Van der Waals Equation
- Practice Question
- Diffusion and Effusion
- Diffusion
- Effusion
- Graham's Law of Effusion
🧪 Unit 4: Chemical Reactions
👟 Unit 5: Kinetics
🔥 Unit 6: Thermodynamics
⚖️ Unit 7: Equilibrium
🍊 Unit 8: Acids and Bases
Unit 9: Applications of Thermodynamics
🤺 AP Chemistry Essentials
🧐 Multiple Choice Questions
✏️ Blogs
continue learning
Join Our Discord
Fiveable Community students are already meeting new friends, starting study groups, and sharing tons of opportunities for other high schoolers. Soon the Fiveable Community will be on a totally new platform where you can share, save, and organize your learning links and lead study groups among other students!🎉
*ap® and advanced placement® are registered trademarks of the college board, which was not involved in the production of, and does not endorse, this product.
© fiveable 2021 | all rights reserved.
2550 north lake drive
suite 2
milwaukee, wi 53211