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Acids, bases and salts

Science, Grade 6

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Study Guide Acids, bases and salts Science, Grade 6

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ACIDS, BASES AND SALTS Acids An acid is a compound that is defined by its physical and chemical properties. Acids taste sour and react with metals and polyatomic ions called carbonates. A carbonate is a charged cluster of Carbon and Oxygen atoms. In addition, when tested with blue litmus paper, acids turn the paper red. Bases A base or hydroxide, like an acid, is also defined by its properties. Bases taste bitter, are slippery to the touch and turn red litmus paper blue. An example of a base is NaOH or sodium hydroxide. Lesson Checkpoint: What are the two names for the substance that turns red litmus paper blue? Common Uses of Acids and Bases Acids and bases have many uses. Acids can be used to clean brick and metal and are an important ingredient in fertilizers. H2SO4 or sulfuric acid is used in car batteries. Bases are used in the construction industry to make cement and are used around the home in drain cleaners and glass cleaners. In the baking industry, the base, baking soda, is used to create the gas bubbles that make dough rise. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

In Solutions In water solutions, acids break down into ions or charged atoms. In the example below, Hydrochloric acid in water has broken down into a Hydrogen ion and a Chlorine ion. It is the Hydrogen ion that gives acids their chemical properties. HCl  H+ + Cl- Bases in solution behave the same as acids. In the example below Potassium hydroxide has broken down into a potassium ion and a hydroxide ion. KOH  K+ + OH- In the case of bases, it is the hydroxide ions that give bases their properties. Acids and bases vary in strength depending on the degree to which they break down into ions in solution. The more acid or base molecules that break down, the stronger is the acid or base. Lesson Checkpoint: What determines the strengths of an acid or base in solution? The pH Scale The strength of an acid or base can be measured on the pH scale. On this scale, numbers 1-7 indicate acids, 7 is considered neutral and 7- 14 indicate a base. On the scale below, hydrochloric acid, with the lowest pH, is the strongest acid and drain cleaner, with a very high pH, is the strongest base. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

In our bodies, pH is important for the digestion of food. Low pH numbers in the stomach help the body break down proteins. When food gets to the small intestine, pH levels are raised above 7 to complete another phase of digestion. When an acid combines with a base a double replacement reaction takes place. In this type of reaction, called neutralization, an acid and a base become salt and water. See this reaction below. Reactants Products In this reaction, HCl, hydrochloric acid, is reacting with sodium hydroxide. NaCl , sodium chloride, is the salt formed from the negative ion of the acid (Cl-) and the positive ion of the base (Na+). All salts are formed in this manner. Lesson Checkpoint: What happens when an acid and a base combine? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.