Chemical Reactions and Energy Transfer

Question 1. Which of the following is an example of an endothermic reaction?

• A. Burning wood

• B. Photosynthesis in plants

• C. Combustion of gasoline

• D. Freezing water into ice

Question 2.

"In a reaction, the energy level of the products is lower than the reactants, and the difference in energy is released as heat."
Identify the type of reaction described.

(a)  

Question 3.

"Mixing baking soda and vinegar produces bubbles and causes the temperature of the solution to drop."

Identify the type of the following reaction.

(a)  

Question 4. Why does dissolving salt in water feel cooler to the touch?

• A. It releases energy as heat.

• B. It absorbs energy from the surroundings.

• C. Salt increases the water’s temperature.

• D. The salt particles heat up rapidly.

During a camping trip, Jake lights a piece of firewood. As the fire burns, he notices that the surroundings feel warmer, and the wood turns into ash, releasing smoke and light.

Question 5.
What type of reaction occurs, and what is happening to the energy in this process?

• A. Endothermic, because energy is absorbed to produce heat and light.

• B. Exothermic, because energy is released in the form of heat and light.

• C. Endothermic, because the wood absorbs energy and turns into ash.

• D. Neutralization, because the fire balances the energy in the surroundings.

Question 6. Predict what would happen if a reaction absorbs more energy than it releases. How would you detect this change?

Maria is conducting a simple experiment in her science class. She mixes 50 mL of vinegar with a teaspoon of baking soda in a beaker. As soon as she combines the two substances, bubbles form rapidly, and the beaker feels cooler to the touch.

Question 7.
What type of reaction is happening in Maria's experiment?

• A. Exothermic, because energy is released as bubbles form.

• B. Endothermic, because the solution absorbs energy, causing the beaker to feel cooler.

• C. Exothermic, because the reaction gives off light.

• D. Neutralization, because the reaction balances the pH of the solution.

In a fireworks display, chemical reactions produce bright lights, heat, and sound.

• Question 8. How does this process follow the law of conservation of energy?

When you dissolve salt in water, the temperature of the water slightly decreases.

• Question 9. What type of energy change is this, and why does it happen?

Question 10. Which statement is true about chemical reactions and mass?

• A. Mass is lost in exothermic reactions.
  

• B. Mass is gained in endothermic reactions.

• C. The mass of the products equals the mass of the reactants.

• D. The mass of the system changes depending on energy changes.