Key Concepts - Chemical Reactions:
- A physical change, such as a state change or dissolving, does not create a new substance, but a chemical change does.
- In a chemical reaction, the atoms and molecules that interact with each other are called reactants.
- In a chemical reaction, the atoms and molecules produced by the reaction are called products.
- In a chemical reaction, only the atoms present in the reactants can end up in the products. No new atoms are created, and no atoms are destroyed.
- In a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.
Key Concepts - Controlling the Amount of Reactant in a Chemical Reaction:
- Changing the amount of reactants affects the amount of products produced in a chemical reaction.
- In a chemical reaction, only the atoms present in the reactants can end up in the products.
- Mass is conserved in a chemical reaction.
Key Concepts - Using Chemical Change to Identify an Unknown:
- Substances react chemically in characteristic ways.
- A set of reactions can be used to identify an unknown substance.
Key Concepts - pH and Color Change:
- Whether a solution is acidic or basic can be measured on the pH scale, which is a scale of 1 to 14.
- A solution with a pH of 7, like water, is called a neutral solution.
- Acidic solutions have a pH below 7 on the pH scale (1-6).
- Basic solutions have a pH above 7 on the pH scale (8-14).
- When a(n) universal indicator (such as cabbage juice or a pH strip) is added to a solution, the color change can indicate the approximate pH of the solution.
- Acids cause a universal indicator solution such as cabbage juice to change from green (basic) toward red.
- Bases cause a universal indicator solution such as cabbage juice to change from green toward purple.
- Water molecules (H2O) can interact with one another to form H3O+ ions and OH− ions.
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