Real-life examples of chemical properties and changes

🧪 Quick Study Guide

• 🌡️ Chemical Property: A characteristic of a substance that can be observed during a reaction in which the chemical composition or identity of the substance is changed. Examples include flammability, reactivity with acid, and toxicity.
• 🔥 Chemical Change: Occurs when a substance is transformed into a new substance. This involves the breaking and forming of chemical bonds. Signs include color change, gas production, precipitate formation, and temperature change.
• 🍎 Example 1: Rusting of Iron: Iron reacts with oxygen and water to form iron oxide (rust). This is a chemical change because a new substance is formed. The chemical equation is: $4Fe + 3O_2 + 6H_2O \rightarrow 4Fe(OH)_3$
• 🍌 Example 2: Burning of Wood: Wood reacts with oxygen in a combustion reaction to produce carbon dioxide, water, and heat. This is a chemical change because the wood is converted into different substances.
• 🥛 Example 3: Milk Souring: Bacteria in milk produce lactic acid, causing the milk to sour. This is a chemical change because the lactic acid alters the composition of the milk.
• 🧪 Key Indicators of Chemical Change:
  • 💨 Evolution of a gas (bubbles)
  • 🌈 Formation of a precipitate (solid)
  • 🌡️ Change in temperature (exothermic or endothermic)
  • 🎨 Change in color

Practice Quiz

1. Which of the following is an example of a chemical property?
   1. A. Density
   2. B. Flammability
   3. C. Melting Point
   4. D. Hardness
2. What is the primary indicator of a chemical change?
   1. A. Change in state (solid, liquid, gas)
   2. B. Change in mass
   3. C. Formation of a new substance
   4. D. Change in volume
3. Rusting of iron is an example of what type of change?
   1. A. Physical Change
   2. B. Chemical Change
   3. C. Phase Change
   4. D. Nuclear Change
4. Which of the following equations represents the rusting of iron?
   1. A. $Fe + O_2 \rightarrow FeO_2$
   2. B. $2Fe + O_2 \rightarrow 2FeO$
   3. C. $4Fe + 3O_2 + 6H_2O \rightarrow 4Fe(OH)_3$
   4. D. $Fe_2O_3 \rightarrow 2Fe + \frac{3}{2}O_2$
5. Burning wood is an example of:
   1. A. A physical change producing ash
   2. B. A chemical change releasing energy
   3. C. A phase change from solid to gas
   4. D. A nuclear reaction
6. What process causes milk to sour?
   1. A. Freezing
   2. B. Boiling
   3. C. Bacterial production of lactic acid
   4. D. Evaporation
7. Which of the following is NOT a sign of a chemical change?
   1. A. Change in color
   2. B. Change in shape
   3. C. Production of gas
   4. D. Formation of a precipitate