Question

When vinegar and baking soda react, the mixture becomes cold to the touch and a gas and a new liquid substance are formed.

Which best describes what is occurring in the reaction?

The reaction is chemical and endothermic.
The reaction is chemical and exothermic.
The reaction is non-chemical and endothermic.
The reaction is non-chemical and exothermic




A Venn diagram is used to compare and contrast different topics. The items that are unique to each topic are represented in the separate sections of the circles, and the items that are common to both topics are represented in the center overlapping sections. Harlow creates this Venn diagram comparing and contrasting endothermic and exothermic processes.

Two overlapping circles are labeled on the left endothermic and on the right exothermic. In the left circle are labels requires energy and examples. In the right circle are labels releases energy and examples. In the overlap is the label involve energy.

What can be added to the Examples section of each circle?

Endothermic: ice melting into water, and a heat pack becoming warm
Exothermic: a glow stick glowing, and fireworks exploding
Endothermic: ice melting into water, and an instant ice pack turning cold
Exothermic: fireworks exploding, and gasoline burning
Endothermic: a glow stick glowing, and a heat pack becoming warm
Exothermic: an instant ice pack turning cold, and ice melting into water
Endothermic: gasoline burning, and an instant ice pack turning cold
Exothermic: ice melting into water, and an instant ice pack turning cold



Which of these most likely represents a chemical change?

water boiling
sugars digested by saliva
mud drying to dirt
ice cream melting




Pedro wants to create a chemical reaction between oil and water. He adds oil to a beaker of water and notices that the liquids do not mix. He then shakes the beaker and the drops of oil become suspended through the water for a few moments before returning to their separate layers.

Did Pedro succeed in creating a chemical change?

Yes, because the oil was evenly suspended.
Yes, because the solution was permanently changed.
No, because the oil only briefly mixed with the water.
No, because no new substances were formed.



What must occur in order for a chemical reaction to be specifically classified as endothermic instead of exothermic?

Atoms are rearranged.
Chemical bonds are formed.
Energy is released in the form of heat.
Energy is absorbed in the form of heat.

Answer 1

1) The reaction is chemical and endothermic.
- Vinegar + baking soda produces new substances (CO2, water, acetate) and the mixture gets cold, so heat is absorbed (endothermic).

2) Endothermic: ice melting into water, and an instant ice pack turning cold.
Exothermic: fireworks exploding, and gasoline burning.
- These correctly match processes that absorb heat (melting ice, instant cold packs) versus those that release heat (combustion, explosions).

3) Sugars digested by saliva.
- Digestion is a chemical change (molecules are broken down); the others are physical changes.

4) No, because no new substances were formed.
- The oil and water only physically separated and temporarily emulsified; no chemical reaction occurred.

5) Energy is absorbed in the form of heat.
- Endothermic reactions take in heat from the surroundings (whereas exothermic reactions release heat).