Peka Science

SEKOLAH MENENGAH KEBANGSAAN

SERI BINTANG SELATANSEKOLAH KLUSTER KECEMERLANGAN

ACIDS & ALKALI

NAME : : NURUL SHAZATUL SYAHMI BINTI MOHD. NASIR

CLASS : 2 DAMARTEACHER’S NAME : PUAN NORREHAN BINTI

NAWAWI

INTRODUCTION

ACIDS AND ALKALI IN OUR BODY

In humans and many other animals, hydrochloric acid is a part of the gastric acid secreted

within the stomach to converting the inactive pro-enzyme. Citric acid plays a role in one

famous stomach remedy, or antacid. Antacids are more generally associated with alkaline

substances, used for their ability to neutralize stomach acid. It is also used in the production

of hair rinses and low-pH shampoos and toothpastes. Amino acids combine to make up

proteins, one of the principal components in human muscles, skin, and hair.

HISTORY OF ACIDS AND ALKALI

The concepts of acidity came from the ancient Greeks who defined “sour-tasting”

substances as oxein, which mutated into the Latin word for vinegar, acetum, which became

anglicized to “acid”. Acid substances were eventually found not only to taste sour, but also

to change the color of litmus paper and corrode metals. The concept of alkali - one of the

first people who talked about the alkali was the great "Sleeping Prophet," Edgar Cayce. He

always referred to body detoxification with herbs, colonics, fasting, massage, steam baths

and diet modification with the aim of alkalizing the body.

INDICATOR THAT USES TO SHOW ACID OR ALKALI IN A SUBSTANCE

Litmus Phenolphthalein Methyl Orange Bromophenol Blue Universal Indicator

The pH scale

The Strength of an Acid

The strength of an acid or alkali is shown using a scale of numbers called the pH scale. The

numbers go from 0-14.

An acidic solution has a pH number less than 7

An alkaline solution has a pH number greater than 7

A neutral solution has a pH number of exactly 7.

Universal indicator will change from green to a different colour depending on the pH of the solution you place it in.

ACID

Definition of acidAn acid in common usage is a substance that tastes sour, reacts with metals and carbonates, turns blue litmus paper red, and has a pH less than 7.0 in its standard state.Examples include acetic acid (in vinegar) and sulfuric acid (used in car batteries). Acids can occur in solid, liquid or gaseous form, depending on the temperature. They can exist as pure substances or in solution. Chemicals or substances having the property of an acid are said to be acidic.

Properties of acids1. They are liquids .2. They are solutions of compounds in water.3. If concentrated they can be corrosive4. Acids taste sour (for example, vinegar).5. Turn blue litmus paper red6. Usually react with metals to form salts.7. Acids contain hydrogen ions.8. Turn universal indicator from green to red, and have a ph less than 7.

Uses of acidsThere are numerous uses for acids. Acids are often used to remove rust and other corrosion from metals in a process known as pickling. They may be used as an electrolyte in a wet cell battery, such as sulfuric acid in a car battery. A wasp sting is alkali. It may be neutralized with a weak acid (lemon juice or vinegar).

Some common acids used in your laboratories at school will be: 1. Hydrochloric acid, HCl(aq) 2. Nitric acid, HNO3(aq) 3. Sulphuric acid, H2SO4(aq)

Example of acids around us-Milk (slightly acidic)-Lemon juice, orange juice (citric acid)-Soda-Vinegar-Distilled water

Pictures

ALKALI

Definition of alkali

An alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.

Properties of alkalis1. They feel soapy to touch.2. They are soluble bases.3. Like acids, they can burn the skin.4. They turn red litmus blue - this is how you test for an alkali!5. Alkalis contain hydroxide ions (OH-).6. They taste bitter.7. Turns Universal Indicator from green to blue or purple.

Uses of alkalineSodium Hydroxide is used to make paper, detergents and soap.Potassium Hydroxide is used in farming to make acidic soil more alkaline so that plants will grow better in it.Calcium Carbonate is used as a building material.Magnesium Hydroxide is used to help with stomach aches or indigestion. It makes the contents of a stomach less acidic

Some common alkalis used in laboratories at school will be:1. Sodium hydroxide, NaOH(aq)2. Ammonia, NH3NH4OH(aq)3. Calcium hydroxide, Ca(OH)2(aq)

Example of alkali around us

Toothpaste contains a minimum amount of alkali to kill the acids off in the teeth .Other household items contain alkali such as Black coffee and various oven cleaners.

Bleach Bicabonate of Soda Washing Soda Powder Drain Cleaners

Pictures

Comparing acids and alkali

Corrosive

Only shows it properties in the presence of water

acid alkali

Similarities

difference

Properties of acid and alkali

pH 1 pH 2 pH 3

pH 3 pH 4 pH 5

pH5 pH 5 pH 6

pH 7 pH 8 pH 9

pH 10 pH 11 pH 12

pH 13 pH 14

Properties of acid and alkali

1

Sour (acid) Bitter (alkali)

Properties of acid and alkali

taste

Green leafy vegetables Wild edibles Fresh herbs Grasses Sprouts Sea vegetables Medicinal mushrooms

Lemon juice Beer Soda Vinegar

2

3

Acid Alkali

Properties of acid and alkali

Limus paper

Red (acid) Blue (alkali)

Properties of acid and alkali

pH value

greater than 7Less than 7

Reference

Text book

- Choo Yan Tong , 2003 , Science Form 2 , Volume Two , Selangor Darul Ehsan .

Reference book

- Peter Ling Chee Chong , 2004 , Exploring Science Revised Edition Form 2 , Selangor Darul Ehsan .

- Choo Yan Tong , 2006 , Latihan U Masteri Science Form 2 , Selangor Darul Ehsan .

Internet

- http://www.google.ca/

- http://en.wikipedia.org/wiki/Wiki