Chemistry problem related to energy?

Question

1. How do joules, calories, and nutritional calories differ?

2. Suppose you combine two solutions in a test tube and they react. How would you determine whether the reaction was endothermic or exothermic?

3. A classmate argues that the burning of charcoal must be an endothermic process because getting the charcoal started requires the input of a large amount of heat. Would you agree? Explain

4. Think of the different methods used to cook food. In what sort of cooking might you want to use cooking utensils with low specific heat? Wher might utensils with high specific heat be useful?

Answer 1

1) 4.18J=1cal 1nutritional calorie=1Cal=1000cal

2) if the test tube is becomes cooler, it's endothermic. if the test tube becomes warmer, its exothermic

3) You would disagree of course. The activation energy is high but the amount of heat and light generated by the reaction is much greater than the required input energy

4) You would want low specific heat in your pots and pans because you heat them up and they heat the food. (The stove heats the bottom of the pan which then heats the food). You want a low specific heat so that the pan heats up quickly. You would want a high specific heat with utensils that you have to touch while hot. The handle of pots and pans have high specific heats. Long stirring spoons and spatulas have high specific heats as well.

Answer 2

1. One calorie = 4.148 joules. One nutritional calorie = 1000 calories.

2. By the temperature change.

3. No. The energy you add at the beginning just supplies the necessary "energy of activation." The reaction will give off much more heat than you need to add to start the reaction.

4. Your guess is as good as mine, good luck.