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Acids & Bases

Science, Grade 5

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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 www.newpathlearning.com 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 www.newpathlearning.com Acids & Bases \|xiBAHBDy01733sz\

Acids & Bases

Science, Grade 5

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