Peka science


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Peka science

  2. 2. INTRODUCTIONACIDS AND ALKALI IN OUR BODYIn humans and many other animals, hydrochloric acid is a part of the gastric acid secretedwithin the stomach to converting the inactive pro-enzyme. Citric acid plays a role in onefamous stomach remedy, or antacid. Antacids are more generally associated with alkalinesubstances, used for their ability to neutralize stomach acid. It is also used in the productionof hair rinses and low-pH shampoos and toothpastes. Amino acids combine to make upproteins, one of the principal components in human muscles, skin, and hair.HISTORY OF ACIDS AND ALKALIThe 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 becameanglicized to “acid”. Acid substances were eventually found not only to taste sour, but alsoto change the color of litmus paper and corrode metals. The concept of alkali - one of thefirst people who talked about the alkali was the great "Sleeping Prophet," Edgar Cayce. Healways referred to body detoxification with herbs, colonics, fasting, massage, steam bathsand diet modification with the aim of alkalizing the body.INDICATOR THAT USES TO SHOW ACID OR ALKALI IN ASUBSTANCE • Litmus • Phenolphthalein • Methyl Orange • Bromophenol Blue • Universal Indicator
  3. 3. The pH scaleThe Strength of an AcidThe strength of an acid or alkali is shown using a scale of numbers called the pH scale. Thenumbers go from 0-14.An acidic solution has a pH number less than 7An alkaline solution has a pH number greater than 7A neutral solution has a pH number of exactly 7.Universal indicator will change from green to a different colour depending on the pH of thesolution you place it in.
  4. 4. ACIDDefinition 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). Acidscan occur in solid, liquid or gaseous form, depending on the temperature. They can exist aspure substances or in solution. Chemicals or substances having the property of an acid aresaid 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 aspickling. They may be used as an electrolyte in a wet cell battery, such as sulfuric acid in acar battery. A wasp sting is alkali. It may be neutralized with a weak acid (lemon juice orvinegar).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 waterPictures
  5. 5. ALKALIDefinition of alkaliAn alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Someauthors also define an alkali as a base that dissolves in water. A solution of a soluble basehas 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 plantswill 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 thecontents 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 usToothpaste contains a minimum amount of alkali to kill the acids off in the teeth .Otherhousehold items contain alkali such as Black coffee and various oven cleaners. • Bleach • Bicabonate of Soda • Washing Soda • Powder • Drain CleanersPictures
  6. 6. Comparing acids and alkali Similarities • Corrosive • Only shows it properties in the presence of water difference acid alkali
  7. 7. Properties of acid and alkali pH 1 pH 2 pH 3 pH 3 pH 4 pH 5 pH5 pH 5 pH 6
  8. 8. pH 7 pH 8 pH 9 pH 10 pH 11 pH 12 pH 13 pH 14
  9. 9. Properties of acid and alkali1 Properties of acid and alkali taste Sour (acid) Bitter (alkali) t Green leafy vegetables • Lemon juice t Wild edibles Fresh herbs • Beer Grasses • Soda Sprouts • Vinegar Sea vegetables Medicinal mushrooms
  10. 10. 2 Properties of acid and alkali Limus paper • Red (acid) • Blue (alkali)3 Properties of acid and alkali pH value Acid Alkali Less than 7 greater than 7
  11. 11. Reference • Text book- Choo Yan Tong , 2003 , Science Form 2 , Volume Two , SelangorDarul Ehsan . • Reference book- Peter Ling Chee Chong , 2004 , Exploring Science RevisedEdition Form 2 , Selangor Darul Ehsan .- Choo Yan Tong , 2006 , Latihan U Masteri Science Form 2 ,Selangor Darul Ehsan . • Internet-