7th Grade Chemical Changes test questions with answers

📚 Quick Study Guide

• 🔥 Chemical Change Definition: A chemical change results in the formation of new substances with different properties.
• ⚛️ Key Indicators: Look for clues like color change, gas production (bubbles), precipitate formation (solid forming in a liquid), temperature change (heat absorbed or released), and light emission.
• 🧪 Examples: Rusting of iron, burning wood, cooking an egg, baking a cake, and mixing vinegar and baking soda are all examples of chemical changes.
• ⚖️ Law of Conservation of Mass: In a chemical reaction, matter is neither created nor destroyed. The total mass of the reactants equals the total mass of the products.
• 📝 Chemical Equations: Chemical reactions can be represented using chemical equations. For example, the reaction of hydrogen and oxygen to form water is: $2H_2 + O_2 \rightarrow 2H_2O$.
• 🌡️ Endothermic vs. Exothermic Reactions: Endothermic reactions absorb heat from the surroundings (feel cold), while exothermic reactions release heat to the surroundings (feel warm).
• 💡 Reactivity Series: Some metals are more reactive than others. A more reactive metal can displace a less reactive metal from its compounds.

Practice Quiz

1. Which of the following is an example of a chemical change?
   1. Melting ice
   2. Boiling water
   3. Burning wood
   4. Dissolving sugar in water
2. What is a key indicator of a chemical change?
   1. Change in state (solid, liquid, gas)
   2. Change in mass
   3. Formation of a new substance
   4. Change in volume
3. Which of the following is an example of an exothermic reaction?
   1. Melting ice
   2. Boiling water
   3. Burning gasoline
   4. Dissolving salt in water
4. What law states that matter is neither created nor destroyed in a chemical reaction?
   1. Law of Definite Proportions
   2. Law of Multiple Proportions
   3. Law of Conservation of Energy
   4. Law of Conservation of Mass
5. Which of the following observations would suggest a chemical change has occurred?
   1. The substance changes shape.
   2. The substance changes color.
   3. The substance changes size.
   4. The substance remains the same.
6. Vinegar and baking soda reacting and producing bubbles is an example of what?
   1. Change of State
   2. Physical Change
   3. Chemical Change
   4. Melting
7. Which of the following is NOT a sign of a chemical change?
   1. Change in color
   2. Change in state
   3. Formation of precipitate
   4. Production of gas