Aim: How can indicators be used to tell if a substance is present? DO NOW: Have you ever used an indicator before? If so, which one? What was it used for? 2. What does the pH scale represent?

Indicators Used to tell if a substance is present, such as sugar or starch Common Indicators used in Living Environment: Lugol’s Solution & Benedict’s Solution

Lugol’s Solution Original color: amber or brown Starch indicator solution Also called iodine solution Turns blue-black in the presence of starch

Benedict’s Solution Original Color: blue Sugar (glucose) indicator solution Turns to green, yellow, orange, & then brick red if a simple sugar is present This chemical reaction is sped up with heat (a hot water bath could be used)

pH Paper Tells whether a liquid is acid, base, or neutral pH paper is dipped into the liquid See what color the pH paper turns into Color is matched to colors on a scale & the pH value for the liquid would be determined

pH Scale

Review Questions What range of numbers does the pH scale include? What pH value range is for acids? What pH value range is for bases? What pH value is for neutral solutions? Which indicator solution is used for sugar detection? Give an example of a common substance that is an acid.

BrainPop Video https://www.brainpop.com/science/matterandchemistry/phscale/

Homework Q1. Textbook page 165, question 3 Q2. Using one or more complete sentences, state what substance a student could use to test for the presence of starch in a food sample and describe the positive result of this test. Q3. A technique that can be used to compare the DNA of two or more plants is _______________________. Q4. A student is heating a test tube containing a crushed cracker and Benedict’s solution. The student is wearing safety goggles and a laboratory apron. Using one or more complete sentences, state one other safety precaution the student should observe.