What Happens to the Food We Eat?

1. What happens to the food we eat?
2. How does our food give us energy?
3. How does matter change as it is digested?

1. Distinguish between physical and chemical changes in matter in the digestive system.
2. Recognize how large molecules are broken down into smaller molecules during digestion.

Background Information:

Before food reaches the small intestine, it is digested mechanically in the mouth and the stomach. The food mass is reduced to small particles. You can chew an apple into small pieces but you wouldn’t feed apple sauce to a small child who didn’t have teeth. What is the advantage of reducing the size of food material?

The action of chewing mechanically breaks down very large food particles into smaller particles. This results in the food having increased surface area, an important contributing factor to good digestion.

Food's contact with saliva is important because it helps to lubricate the food, making it easier for foods to pass easier through the esophagus. It's also important because saliva contains enzymes that contribute to the chemical process of digestion. The chemical digestion of carbohydrates and fats begin with enzymes in your saliva. The smaller the particles are, the faster the chemical digestion. Why? When you decrease the size of the particles you increase the surface area of the food. More surface area means the saliva comes into contact with more food and can chemically digest it faster.

When food is not well chewed and the food fragments are too big to be properly broken down, incomplete digestion occurs. If food particles are too big, nutrients will not properly absorb into the bloodstream while in the small intestine. In addition, undigested food can cause too much bacteria to grow in your large intestine causing gas and other unpleasant symptoms.

Problem: How does reducing the size of food particles aid the process of digestion?

Hypothesis: ______

Materials:

Lab modified from:

Glencoe Science 7th grade, pg 488

3 beakers or jars

3 thermometers

Sugar granules

Mortar and pestle

Triple beam balance

Stirring rod

Sugar cubes

Weighing paper

Warm water

Stopwatch

Lab modified from:

Glencoe Science 7th grade, pg 488

Lab modified from:

Glencoe Science 7th grade, pg 488

Procedure:

1. Place sugar cube into your mortar and grind up the cube with the pestle until the sugar becomes powder.
2. Using the triple-beam balance and weighing paper, measure the mass of the powdered sugar from your mortar. Using separate sheets of weighing paper, measure the mass of a sugar cube and the mass of a sample of granular sugar. The masses of the powdered sugar, granular sugar and sugar cube should be approximately equal to each other.
3. Record the 3 masses in your data table.
4. Place warm water into the three beakers. Use the thermometers to be certain the water in each beaker is the same temperature.
5. Place the sugar cube in a beaker, the powdered sugar in a second beaker, and the granular sugar in the third beaker. Place all the sugar samples in the beakers at the same time and start the stopwatch when you put the sugar samples in the beaker.
6. Stir each sample equally.
7. Measure the time it takes each sugar sample to dissolve and record the times in your data table.

Data Table:

Conclude and Apply

1. Identify the experiment’s constants and variables.

1. Compare the rate at which the sugar samples dissolved. What type of sugar dissolved most rapidly? Which was the slowest to dissolve?

1. Identify the type of digestion demonstrated in this investigation.
   Chemical or Mechanical. ______

1. Infer why you should thoroughly chew you food.

1. Explain how reducing the size of food particles aids the process of digestion.

Lab modified from:

Glencoe Science 7th grade, pg 488