both the esophagus and the small intestine are involved in the digestion of food.  the esophagus squeezes food into the stomach by wave-like muscle contractions.  peptidase enzymes in the small intestine break food molecules into smaller molecules.

which statement best describes changes to food during digestion?

  a. 

the muscle contractions result in chemical changes, while the action of the peptidase results in physical changes.

  b. 

the muscle contractions result in physical changes, while the action of the peptidase results in chemical changes.

  c. 

the muscle contractions and the action of the peptidase both result only in chemical changes.

  d. 

the muscle contractions and the action of the peptidase both result only in physical changes.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante