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Acids & Bases

Science, Grade 5

Hydroxide ion (–) neutral strong acid strong base 1 2 3 4 5 9 6 7 8 14 13 12 11 10 litmus paper Every liquid has traits of an acid or a base. An acid is a type of sour substance. Many of the foods we eat such as oranges and tomatoes contain weak acids. When placed in water, acids release hydrogen (H+) ions into the water. Ions are negatively or positively charged atoms. When an acidic substance dissolves in water hydrogen atoms break away from the acid molecules. This process forms hydrogen ions. The more hydrogen ions formed, the stronger the acid. Some Characteristics of ACIDS: Acids taste sour Acids react strongly with metals Change blue litmus paper to red A base is a type of bitter substance. When placed in water, bases release hydroxide (OH-) ions into the water. Examples of a base include soap and baking soda. Some Characteristics of BASES: Bases taste bitter Bases often have a slippery feel Change red litmus paper to blue Identification of Acids & Bases Scientists use a pH scale to measure the strength of acids and bases. The pH scale ranges from 0 to 14. Substances with pH of less than 7 are considered acids; the lower the pH, the stronger the acid. The pH of bases ranges from 7-14; the higher the pH the stronger the base. Neutral solutions have a pH of exactly 7. pH Indicators Scientists use a variety of pH indicators to determine which substances are basic and acidic. pH indicators are chemicals that change color in the presence of an acid or base. A strong acid will turn the universal pH indicator paper red. A strong base will turn the universal indicator paper purple. 1 13 14 10 9 12 11 8 7 5 6 4 3 2 pH Scale HCl NaOH Scientists use a pH scale to measure how acidic or basic a substance is. A strong Acid has a very low pH (0-4). A strong Base has a very high pH (10-14). A neutral solution has a pH of 7 it is not an acid or a base. Litmus paper is another type of pH indicator. Blue litmus paper turns red when dipped into an acid. Red litmus paper turns blue in the presence of a base. Warning!!! DO NOT TOUCH OR TASTE SUBSTANCES during science experiments. Strong acids and bases are dangerous! They can burn your skin instantly when touched! Acids Bases (–) O H © Copyright NewPath Learning. All Rights Reserved. 94-4508 Acids & Bases (+) H
1 2 3 4 5 9 6 7 8 14 13 12 11 10 (+) 1 13 14 10 9 12 11 8 7 5 6 4 3 2 HCl NaOH Some Characteristics of ACIDS: 1. ____________________________________________ 2. ____________________________________________ 3. ____________________________________________ Identification of Acids and Bases What is a pH scale and how is it used? _____________________________________________________ _____________________________________________________ pH Indicators What are pH indicators and how are they used? ______________________________________________________ ______________________________________________________ What is universal pH indicator paper? ______________________________________________________ ______________________________________________________ What is blue litmus paper? ______________________________________________________ ______________________________________________________ What is red litmus paper? ______________________________________________________ ______________________________________________________ Key Vocabulary Terms acid base hydrogen ion hydroxide ion litmus paper negative charge neutral pH indicator pH scale positive charge universal indicator (–) © Copyright N ewPath Learning. All Rights Reserved. 94-4508 Acids & Bases \|xiBAHBDy01733sz\