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Physical and Chemical Changes of Food in the Digestive Tract Prepared by: Mrs. Lucia Traya 7 Grade Science WAMS THE DIGESTIVE SYSTEM Mouth- Physical digestion or change of food materials: Teeth grind food down to smaller pieces - Chemical digestion or change of food materials: Enzymes in saliva called amylase breaks down some of the food like starch before it travels down the esophagus. Stomach- Physical digestion occurs when muscles in stomach churn food. - Chemical digestion occurs when stomach acids, gastric juices, and enzymes break down food and breaking its molecular structures forming another substance. Small Intestines- Chemical digestion occurs to food materials due to the chemical secretion/production of pancreatic juices, bile a chemical substance produced by the liver, as well as other enzymes that break down food so it can be easily absorbed by the cells. Large Intestines- Physical digestion occurs when the walls of the large intestines absorb the water and minerals, and feces the waste product of digestion is temporarily stored then pushed out of through the anus. X the Changes Example Breaking food into smaller pieces by the teeth Hydrochloric acid breaking down the food in stomach Removal of water from food materials in the large intestines Breaking down food into starches when mixed with saliva Pancreatic juices neutralize acid in the small intestines Continual mixing of food materials in the intestine Churning and mixing of food in the stomach Water and digestive enzymes break down fats, proteins, and carbohydrates into smaller molecules Physical Chemical Summary: When food enters the mouth, the process of chewing mechanically/physically breaks food down into smaller pieces. The act of chewing releases saliva from the salivary glands in the mouth. Saliva contains enzymes that chemically break down starch or carbohydrates in food. When food travels to the stomach, it mixes with acids and other enzymes that break down food chemically. The muscles in the stomach physically churn the food. When food enters the small intestine it comes in contact with enzymes from the liver and pancreas. These enzymes from the liver and pancreas work to break down food chemically for easier absorption of nutrients into into the villi of the walls of the small intestines. Food materials that cannot be digested passes through the Large intestine. The large intestine also absorbs water and Minerals before it compacts the waste material for excretion or removal through the anus.