1. CLASS SET
CLASS SET
Physical and Chemical Changes in the Digestive System
Reading to Learn: Read the following passage and answer the questions that follow.
Terms to Know:
1. Digestion: is the process where food is broken down by the digestive system into small nutrients to be absorbed by the body.
2. Nutrients: are very tiny molecules that are broken down from large molecules to be absorbed and used by body cells.
Two Types of Digestion
Type 1 - Mechanical digestion: Changes the physical form of food (physical changes)
Type 2 - Chemical digestion: Changes the chemical composition of food into a new substance with the aid of digestive enzymes (chemical changes).
Mechanical Digestion = Physical Change
Takes place inside the mouth where teeth and tongue breakdown food.
Examples of Physical Changes:
Chew
Tear
Grind
Chemical Digestion = Chemical Change
The salivary glands secrete mucus and an enzyme called saliva that breaks down carbohydrates in to sugar.
Mash
Mix
Crush
Esophagus
The esophagus is a muscular tube. As we swallow, we push food along the tube until the food reaches our stomach. This process of pushing down the food is called peristalsis
Peristalsis: A type of physical (mechanical) digestion in which food is squeezed through your digestive tract; like from your esophagus into your stomach
Stomach
The stomach mixes the Food with gastric juices called pepsin to form chyme. The chemical digestion of proteins begins in the stomach.

2. CLASS SET Small Intestines
Where fat molecules are broken down into smaller molecules. Which is an example of chemical digestion.
The remaining food is pushed down (peristalsis) to exit the digestive system. Which is an example of physical digestion.
Large Intestine
Where excess water is removed before eliminating waste. Which is an example of physical digestion.
Checkpoint 1: Answer questions 1-7 on the student checkpoint worksheet.
Which type of digestion?
Chewing a saltine?
Saliva breaking the saltine down into molecules of glucose?
Fat molecules broken down into smaller molecules in the small intestine?
Your tongue breaking pieces of a hamburger apart?
Excess water being removed by the large intestine?
Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids?
Peristalsis occurring in the esophagus?
Why Do We Eat?
The food we eat has chemical energy stored in it.
This energy is released by breaking the food down by the digestive system.
The law of conservation of energy states: Energy can’t be destroyed or created. Energy changes forms.
Your body uses this released energy to:
Walk, Jump, Talk, Breath by changing Chemical energy Mechanical energy.
Also to generate body heat by changing Chemical energy Heat energy.
CLASS SET

3. CHECKPOINTS: Physical and Chemical Changes in the Digestive System
Checkpoint 1: Answer questions 1-7 by filling in the blanks using Mechanical or Chemical Digestion.
Which type of digestion?
_______________ Chewing a saltine
_______________ Saliva breaking the saltine down into molecules of glucose
_______________ Fat molecules broken down into smaller molecules in your small intestine
_______________ Your tongue breaking pieces of a hamburger apart
_______________ Excess water being removed by your large intestine
_______________ Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids
_______________ Peristalsis occurring in your esophagus
Checkpoint 2: Reading Comprehension - Complete the chart below using information from the reading assignment.
Structure
Function(s)
Type of Digestion
Type of Change
Mechanical
Chemical
Physical
Mouth
Esophagus
Stomach
Small Intestine
Large Intestine
Name ______________________________________Date _________________Period_____
Checkpoint 3: Energy Transformations – Describe two energy transformations that occur as a result of digestion.
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