Everyday examples of elements and compounds for 7th graders.

📚 Quick Study Guide

• ⚛️ Elements: Pure substances that cannot be broken down into simpler substances by chemical means. Examples include gold (Au), oxygen (O), and carbon (C).
• ⚗️ Compounds: Substances formed when two or more elements are chemically bonded together in a fixed ratio. Compounds can be broken down into simpler substances through chemical reactions.
• 💧 Water ($H_2O$): A compound made of two hydrogen atoms and one oxygen atom. It's essential for life.
• 🧂 Salt (Sodium Chloride, $NaCl$): A compound made of sodium and chlorine. It's used to flavor food.
• 💨 Carbon Dioxide ($CO_2$): A compound made of carbon and oxygen. Plants use it during photosynthesis.
• 💎 Difference: Elements are the simplest form of matter, while compounds are combinations of elements. The properties of a compound are different from those of its constituent elements.
• 💡 Tip: Remember that compounds have a fixed chemical formula, indicating the exact ratio of elements present.

🧪 Practice Quiz

1. Which of the following is an example of an element?
   1. Water ($H_2O$)
   2. Salt ($NaCl$)
   3. Gold ($Au$)
   4. Sugar ($C_{12}H_{22}O_{11}$)
2. What is table salt ($NaCl$) an example of?
   1. An element
   2. A compound
   3. A mixture
   4. An alloy
3. Which compound is essential for photosynthesis in plants?
   1. Water ($H_2O$)
   2. Oxygen ($O_2$)
   3. Carbon Dioxide ($CO_2$)
   4. Nitrogen ($N_2$)
4. Vinegar is a solution of acetic acid ($CH_3COOH$) in water. Acetic acid is a:
   1. Element
   2. Compound
   3. Mixture
   4. Alloy
5. What elements make up the compound water ($H_2O$)?
   1. Hydrogen and Oxygen
   2. Carbon and Hydrogen
   3. Sodium and Chlorine
   4. Carbon and Oxygen
6. Sugar ($C_{12}H_{22}O_{11}$) is commonly used in baking. Is sugar an element or a compound?
   1. Element
   2. Compound
   3. Mixture
   4. Alloy
7. Which of the following is NOT a compound?
   1. Methane ($CH_4$)
   2. Helium ($He$)
   3. Ammonia ($NH_3$)
   4. Ethanol ($C_2H_5OH$)