Take out your Lab Station 6: X- means no check- means yes TestUnknown #1Unknown #2Unknown #3Unknown #4Unknown #5Unknown #6 Cohesion Adhesion Solvent Conclusions (water or not?)

2 What is pH? ACIDS & BASES

Journal Week: 3, Tuesday 9/11 List 3 items/solutions/foods you believe to be acidic List 3 items/solutions/foods you believe to be acidic List 3 items/solutions/foods you believe to be basic List 3 items/solutions/foods you believe to be basic EXPLAIN WHY?! EXPLAIN WHY?! Make a “ T CHART” that looks like this: Make a “ T CHART” that looks like this: AcidsBases AcidsBases

Some of our favorite foods make our tongue curl up because they are SOUR. Some of our favorite foods make our tongue curl up because they are SOUR. Acids and Bases 4

Bitter! Some foods have a “bite” of their own because they’re somewhat bitter. Some foods have a “bite” of their own because they’re somewhat bitter. WHY? WHY? 5

Acidic/Basic There is a scientific reason for this: There is a scientific reason for this: These foods are either acidic or basic. These foods are either acidic or basic. Other substances besides foods have these characteristics. Other substances besides foods have these characteristics. 6

Acids and Bases Chemicals may be classed as acids or bases. Chemicals may be classed as acids or bases. Things that are neither acids nor bases are neutral. Things that are neither acids nor bases are neutral. pH measures how acidic or basic a solution is. pH measures how acidic or basic a solution is. 7

Acids Often taste sour * Often taste sour * Strong acids can burn skin & eyes Strong acids can burn skin & eyes Strong acids can dissolve metals Strong acids can dissolve metals Examples: Examples: Lemon juice Lemon juice Vinegar Vinegar Milk Milk Car battery acid Car battery acid (dangerous!) *Never test an unknown acid by tasting it! 8

Bases Can taste bitter, sweetish, or salty * Often feel slippery or “soapy” * Strong bases can burn skin & eyes Bases react more easily with protein than with metal; they are often used for cleaning Examples: Baking soda Soap Drain cleaner (dangerous!) *Never test an unknown base by touching or tasting it! 7

No I am Not: Some substances are not really an acid or a base: For example, pure water Some substances are not really an acid or a base: For example, pure water 10

Journal Week: 3, Wednesday 9/12 Get a Green Book Get a Green Book Draw a pH scale Draw a pH scale Label: Acid range, Strong Acid, Base range, Strong base, & neutral. Label: Acid range, Strong Acid, Base range, Strong base, & neutral.

pH A special name is given to the acid or base characteristic that a substance has: A special name is given to the acid or base characteristic that a substance has: It is called: pH It is called: pH 12

How Do We Measure pH? We measure pH by using special strips of paper called pH paper We measure pH by using special strips of paper called pH paper 13

How Does It Work? The paper is treated with chemicals that change color to show the pH. The paper is treated with chemicals that change color to show the pH. When the paper touches the substance being tested, it turns a specific color to tell if the substance is an acid or a base. When the paper touches the substance being tested, it turns a specific color to tell if the substance is an acid or a base. 14

Acid Any substance which has a pH of value of less than 7 is considered an acid Any substance which has a pH of value of less than 7 is considered an acid Acid Neutral Base Acid Neutral Base 15

Base Any substance which has pH value greater than 7 is a base Any substance which has pH value greater than 7 is a base Acid Neutral Base Acid Neutral Base 16

pH 7 A pH of 7 is called neutral—neither acid nor base. A pH of 7 is called neutral—neither acid nor base Acid Neutral Base Acid Neutral Base 17

The pH Scale pH scale ranges from pH 7 is neutral; neither acid nor base Pure water is pH 7 Low pH = acid High pH = base The closer to the ends of the scale, the stronger the solution is 18

The pH Scale 19

The pH Scale Each pH unit is 10 times as large as the previous one Each pH unit is 10 times as large as the previous one A change of 2 pH units means 100 times more basic or acidic A change of 2 pH units means 100 times more basic or acidic Each pH unit is 10 times as large as the previous one Each pH unit is 10 times as large as the previous one A change of 2 pH units means 100 times more basic or acidic A change of 2 pH units means 100 times more basic or acidic x10x100 20

The pH Scale Careful measurement is important Careful measurement is important A mistake of one pH unit means too much or too little! A mistake of one pH unit means 10 times too much or too little! x10x100 21

Why is pH important? Soil has to be in a certain pH range for plants to grow and stay healthy. Fish can’t live if the pH is too high or too low 22

pH and People Water that has too high or low pH may contain harmful dissolved chemicals. Water plant operators keep a careful watch on the pH of our drinking water, to keep it safe. Homeostasis Most Importantly to humans is that the pH within our bodies stays within a certain parameter 23

Buffers Buffers The pH of the fluids within most cells in the human body must generally be kept between 6.5 and 7.5. The pH of the fluids within most cells in the human body must generally be kept between 6.5 and 7.5. Controlling pH is important for maintaining homeostasis. Controlling pH is important for maintaining homeostasis. One of the ways that the body controls pH is through dissolved compounds called buffers. One of the ways that the body controls pH is through dissolved compounds called buffers. Buffers are weak acids or bases that prevent sharp, sudden changes in pH. Buffers are weak acids or bases that prevent sharp, sudden changes in pH.

Two papers, two charts The yellow paper reads from pH (base). The colors on this side start with yellow (6.5) The orange paper reads from pH (acid). Use the side of the dispenser that begins with pH 0.0. It’s easy to recognize because the colors begin with shades of orange. Using two different papers gives a more precise reading. 25