Engage: Physical and Chemical Changes
Recall the difference between a physical and chemical change.
Complete the following activity to identify each example as a physical or chemical change. To retake the quiz, reload the page and then select No when the Resume Quiz dialog box appears.
Review items for physical and chemical changes, if needed, can be found in Related Items.
Explore: Digesting Digestion
The process of digestion involves physical and chemical changes to the food 
Click on the picture of the digestive system to explore how digestion breaks down food in our bodies. (Use the Microsoft Internet Explorer browser to access this activity.)
Select at least one food to explore physical and chemical digestion.
Then click on each organ, beginning with the mouth.
Record examples of physical and chemical changes that occur in each organ in your science journal.
An optional note-taking page, Physical and Chemical Changes in Digestion, is available in Related Items.
Explain: Physical and Chemical Changes in Digestion
Physical and chemical changes can occur almost everywhere, even in our bodies!
Our bodies physically and chemically digest food. When food is physically changed, mechanical digestion occurs. Food is broken into smaller parts and mixes continually with enzymes and other gastric juices. Mechanical digestion occurs in the mouth, stomach, and small intestine.
Food is chemically changed in digestion when new, smaller substances are formed. These chemical changes are examples of chemical digestion. Chemical digestion begins in the mouth when enzymes in saliva begin to break down carbohydrates. Most chemical changes in digestion occur in the small intestine. Large molecules of food are broken down into smaller molecules that can be absorbed by our cells. Carbohydrates, proteins, and fats are broken down in different parts of the digestive system using different kinds of enzymes. Different kinds of small molecules are formed by these processes.
Water reabsorption occurs in the large intestine. Bacteria in the large intestine help produce certain vitamins and break down specific materials.
Check your examples of physical and chemical changes with the key below.
Add or make changes to your work if needed.
Elaborate: Classifying Digestive Processes
To retake the quiz, reload the page and then select No when the Resume Quiz dialog box appears.
After the quiz, add or make changes to your physical and chemical digestion notes.
Evaluate: Check Your Knowledge
Complete the evaluate activity by moving each descriptor to its appropriate location.
To retake the quiz, reload the page and then select No when the Resume Quiz dialog box appears.
Teacher Notes
In this lesson, students learn about physical and chemical changes during digestion through a variety of activities. Previously, students learned about physical properties and physical changes in the fifth grade [TEKS 5(5)(A) and 5(5)(D)] and evidence of chemical changes in the sixth grade [TEKS 6(5)(D)]. Students may choose to work through the activities alone, or the teacher may choose to work through the lesson as a small-group or whole-group activity.
| Lesson Phase | Activities |
|---|---|
| Engage | In Engage, students revisit physical and chemical changes and work through an interactive activity to identify physical and chemical changes. Most of the examples relate to digestion. Additional resources are available in Related Items if students need additional review with physical and chemical changes. |
| Explore | In Explore, students integrate their knowledge of physical and chemical changes with digestion. Students explore digestion through an online activity and are encouraged to identify physical and chemical changes. First, students work through an online activity that demonstrates how different foods are broken down. Then, they explore the different organs, determine physical and chemical changes that occur in each organ, and record their findings in their student journals. An optional note-taking page is available in Related Items. Teachers may prefer for students to wear headphones or turn down the speaker volume due to gastric noises and music. |
| Explain | In Explain, students review physical and chemical changes in digestion and make additions or corrections in their journal notes. |
| Elaborate | Students participate in an interactive activity where they classify digestive processes as either physical or chemical. Feedback is provided for each question. Students are encouraged to make additional or changes to their notes. |
| Evaluate | Students create a graphic organizer for chemical changes in digestion in an interactive activity. Teachers may opt for students to create their own graphic organizer/Frayer model on paper first and then complete the interactive Evaluate to compare the two. |
