Section 1: Acids, Bases, and pH Chapter 8: Acids & Bases Tums contains a base that neutralizes stomach acid. Oranges contain citric acid. Section 1: Acids, Bases, and pH

What are they? Most of you are familiar with the term ‘acid’ and ‘base’. But do you know what it really means for a substance to be an acid or a base? Lets start by looking at acids first.

Acids: A close look. Most people think of acids are harmful substances that burn you… In fact, acids CAN be very harmful! But they are very useful as well. When added to water, an acid will ionize, or form ions. Remember that ions have a + or – charge.

Acids and Ions All acids contain Hydrogen in their chemical formula. (Well not ALL of them, but for our course, we will say that all of them do…) When an acid enters water, the Hydrogen ions escape! They will then bond with the water molecules.

Hydronium! Once this happens, the water molecules become hydronium: Hydronium Ions! Water 1+ Add an Acid 1+ 1+ 2- 2- 1+ 1+ 1+ Sketch Me!

Uh…Hydronium?? Definition: hydronium ion – the H3O+ molecule that is created by acids. Hydronium gives acids their properties.

Defining an Acid Now we can define an acid: Definition: acid – a substance that creates hydronium ions when added to water. Acids have a very sour taste. Acids can conduct electricity when in water.

Acids, weak and Strong Acids can be described as weak or strong. A weak acid does not form very many H3O ions in water. A strong acid forms lots of H3O ions in water.

BASES! So, what? Okay, that’s great. Why do we need to know about Hydronium ions and acids? Well: Acids cause powerful chemical reactions when combined with… BASES!

A closer look at Bases Most people are familiar with acids… But lots of people have no idea what a ‘base’ is! When added to water, a base will ionize by to form Hydroxide ions. Definition: hydroxide ion – the OH- ion created by a base.

Hydroxide! Sketch Me! Bases form Hydroxide when dissolved in water: Hydroxide Ions! Water 1+ Add a Base 1+ 1+ 2- 2- Sketch Me!

Defining a Base Definition: base – a special substance that creates hydroxide ions in water. Bases have a bitter & soapy taste. They are slippery when on your hands. They can conduct electricity in water.

Put em together… Now we can see why acids and bases react when put together: Acids  H3O+ Bases  OH- On is positive, and one is negative. When combined, they will… Well, we’ll look at that later.

pH Before looking at how acids and bases react, lets figure out a way to determine how strong they are. Scientists use the pH scale to measure the strength of an acid or base. Definition: pH – a value that measure the strength of an acid/base.

pH – What does it measure? pH means ‘the power of Hydrogen’. It measures the number of Hydronium ions in a solution. The pH scale ranges from 0 to 14. A pH of 7 is neutral. Neutral substances are not acids or bases.

The pH scale. A pH of less than 7 indicates an acid. A pH greater than 7 indicates a base.

Neutral! PURE water has a pH of 7.

Indicators If you need to know whether a substance is an acid or a base, you use an indicator to test it. Definition: indicator a substance used to detect the presence of an acid or a base.

Section 2: Acid/Base Reactions Chapter 8: Acids & Bases Section 2: Acid/Base Reactions

Reactions of Acids/Bases You may already know that acids and bases react with they come in contact. As we know, Hydronium is H3O+… Hydroxide is H3O -. Because acid/base ions have different charges, they can react.

+ Neutralization Sketch Me! When acids and bases react, the hydronium and hydroxide ions bond together. The bonding of these ions creates water molecules. 1+ 1+ 1+ 1+ 2- 1+ 2- + 2- 1+ OH- Base H2O H3O+ Water Acid Sketch Me!

Neutralization So, acids and bases become neutral when combined. These reactions also produce ‘salts’. Definition: salt – an ionic compound formed by the reaction of an acid & base.

+ + Example: Hydrochloric Acid reacts with the base Sodium Hydroxide. The reaction produces water and table salt. HCl + NaOH  H2O + NaCl + +

Section 3: Uses of Acids & Bases Chapter 8: Acids & Bases Section 3: Uses of Acids & Bases

Food Use Acids and bases are used commonly in our daily lives. Many foods contain acids… Most soft drinks, fruits, and juices contain some kind of acid. Contains: Water, High Fructose Corn Syrup and/or Sugar, Citric Acid, Sodium Citrate, Sodium Benzoate and Potassium Sorbate (To Preserve Freshness), Ascorbic Acid (Vitamin C), Glycerol Ester Of Wood Rosin, Natural Flavor, Yellow 5, Ascorbyl Palmitate (Preserves Freshness).

Acid as a Preservative Acids can be used in foods to preserve them…especially fruit.

Acids in our Bodies Acids are also found in living organisms. Food is digested by stomach acid before moving through the body. Many stinging insects inject acid when they sting you. Ants, for instance, inject formic acid.

Uses of Bases Bases have many uses as well. Many household cleaners are bases. Bleach is a very common base.

Soap and Suds Detergents and soaps are also weak bases. These products have pH close to neutral so that they do not harm your skin.

And of course…