What is a Physical Change? • A change from one state to another without a change in what the substance is chemically made of. • Physical Changes do not make new chemical substances and are “reversible” – they can go back to what they originally were. Examples of Physical Changes: • Chewing food • Boiling or freezing water • Melting an ice cube • Cutting or shredding paper • Crushing a Coke can • Breaking a glass • Chopping wood • Mixing sand and water • Mixing red and green marbles • Puddles drying in the sun
What is a Chemical Change? • A change which results in a new substance being made with a new chemical make-up. • A chemical reaction is involved. • Chemical changes are “irreversible” – once the change is made, they can not go back to what they originally were. Examples of Chemical Changes: • Setting off fireworks • Burning wood • Cooking an egg • Baking a cake • Enzymes and acids dissolving crackers in your mouth and stomach • Mixing baking soda and vinegar to produce Carbon Dioxide gas bubbles • Hydrogen & Oxygen making water
What is Mechanical Digestion? • Mechanical Digestion involves tearing, chopping, chewing, turning and churning food around in your mouth and stomach. • Mechanical Digestion is a Physical Change Examples of Mechanical Digestion: • Chewing food with your teeth • Food turning and churning around in your stomach
Occurs when enzymes and different chemicals in your body break down large molecules of food into smaller ones so that the nutrients can be changed into energy which helps keep you healthy and alive • Chemical Digestion is a Chemical Change Examples of Chemical Digestion: What is Chemical Digestion? • Enzymes in your saliva breaking down food in your mouth • Stomach acids breaking down food in your stomach
Wait…Something was said about Food Molecules… What is a molecule? • A molecule is a group of two or more atoms that stick together • Examples of atoms are Carbon (C), Hydrogen (H), and Oxygen (O) • Molecules are so small that nobody can see them, except with a very powerful microscope. These are two different Representations of Glucose Molecules
Your Digestive System The main function of your digestive system is to break larger food molecules into smaller ones that your body can use. For example, a complexCarbohydrate Molecule (carbohydrates are found in breads, pastas, potatoes, rice, and many other foods) can be broken down by your body into smaller, more simple sugar molecules.
Absorption:The nutrients from your food passing through the walls of your digestive system and going into your blood.
The Rectum • The rectum stores feces (poop) for a short time before the feces are released into the anus and out of your body.