Instructions
Welcome to the world of acids and bases! These amazing chemicals are all around us, from the food we eat to the cleaners we use. Read through each section carefully and use the information provided to answer the questions. Let's get started!
Part 1: The Building Blocks
At a chemical level, acids and bases are defined by what they do with hydrogen ions (H+). An acid is a substance that donates, or gives away, hydrogen ions when dissolved in water. A base (also called an alkali) is a substance that accepts hydrogen ions.
Fill in the blanks below to check your understanding.
- A substance that donates hydrogen ions (H+) is called an .
- A substance that accepts hydrogen ions is known as a .
- The chemical symbol for a hydrogen ion is .
Part 2: The pH Scale
The pH scale is a measurement of how acidic or basic a water-based solution is. The scale runs from 0 to 14.
- A pH of 7 is perfectly neutral (like pure water).
- A pH less than 7 is acidic (the lower the number, the stronger the acid).
- A pH greater than 7 is basic or alkaline (the higher the number, the stronger the base).
Categorize the following common items. Based on their typical properties, decide if they are an Acid, a Base, or Neutral.
| Substance | Acid, Base, or Neutral? |
|---|---|
| Lemon Juice (pH ~2) | |
| Pure Water (pH 7) | |
| Soap (pH ~10) | |
| Vinegar (pH ~3) | |
| Baking Soda (pH ~9) | |
| Stomach Acid (pH ~1.5) | |
| Bleach (pH ~13) |
Part 3: Characteristic Properties
Acids and bases have distinct properties that help us identify them. One common tool is litmus paper, a special indicator that changes color in the presence of an acid or a base.
Read the statements below and decide if they are True or False.
- Acids usually have a sour taste, like a lemon.
- Bases feel slippery to the touch, like soap.
- An acid will turn red litmus paper blue.
- A strong base can be just as corrosive and dangerous as a strong acid.
Part 4: Finding the Balance
What happens when you mix an acid and a base? They react in a process called neutralization. The acid and base cancel each other out, producing two neutral substances: a type of salt and water. This is why antacids (which are basic) can help relieve an overly acidic stomach.
Complete the general chemical word equation for a neutralization reaction.
Acid + Base → +
Part 5: Critical Thinking
Many household cleaners are either strong acids (like some toilet bowl cleaners) or strong bases (like bleach or drain cleaner). Why should you never mix different household cleaning chemicals unless the instructions say it is safe?
Answer Key
Part 1: The Building Blocks
- Acid
- Base
- H+
Part 2: The pH Scale
| Substance | Acid, Base, or Neutral? |
|---|---|
| Lemon Juice (pH ~2) | Acid |
| Pure Water (pH 7) | Neutral |
| Soap (pH ~10) | Base |
| Vinegar (pH ~3) | Acid |
| Baking Soda (pH ~9) | Base |
| Stomach Acid (pH ~1.5) | Acid |
| Bleach (pH ~13) | Base |
Part 3: Characteristic Properties
- True
- True
- False (Acids turn blue litmus paper red.)
- True
Part 4: Finding the Balance
Acid + Base → Salt + Water
Part 5: Critical Thinking
Mixing different cleaners, especially an acid and a base (like bleach and a toilet bowl cleaner), can cause a violent chemical reaction. This reaction can release dangerous, toxic gases (like chlorine gas) that are extremely harmful to breathe in and can cause serious injury or even death.