Presentation on theme: "1 Acids and Bases Properties of Matter. Litmus paper - Litmus paper is a pH indicator used to test materials for acidity. Blue litmus turns red in acidic."— Presentation transcript:
Litmus paper - Litmus paper is a pH indicator used to test materials for acidity. Blue litmus turns red in acidic conditions and red litmus turns blue in basic conditions. Acid – a substance that tastes sour, reacts with metals and carbonates, and turns blue litmus paper red. Corrosive – The way in which acids react with some metals so as to eat away the metal. Base – A substance that tastes bitter, feels slippery, and turns red litmus paper blue. Indicator – a compound that changes color in the presence of an acid or a base.
So what makes an acid or a base? A chemist named Svante Arrhenius came up with a way to define acids and bases in 1887. He saw that when you put molecules into water, sometimes they break down and release an H + (hydrogen) ion.hydrogen At other times, you find the release of an OH - (hydroxide) ion. When a hydrogen ion is released, the solution becomes acidic. When a hydroxide ion is released, the solution becomes basic. Those two special ions determine whether you are looking at an acid or a base. For example, vinegar is also called acetic acid. (Okay, that gives away the answer.) If you look at its atoms when it's in water, you will see the molecule CH 3 COOH split into CH 3 COO - and H +. That hydrogen ion is the reason it is called an acid.atoms
pH Scale Scientists use something called the pH scale to measure how acidic or basic a liquid is. Although there may be many types of ions in a solution, pH focuses on concentrations of hydrogen ions (H + ) and hydroxide ions (OH - ). The scale measures values from 0 all the way up to 14. Distilled water is 7 (right in the middle). Acids are found between 0 and 7. Bases are from 7 to 14. Most of the liquids you find every day have a pH near 7. They are either a little below or a little above that mark. When you start looking at the pH of chemicals, the numbers can go to the extremes. If you ever go into a chemistry lab, you could find solutions with a pH of 1 and others with a pH of 14. There are also very strong acids with pH values below 1, such as battery acid. Bases with pH values near 14 include drain cleaner and sodium hydroxide (NaOH). Those chemicals are very dangerous.
pH Scale (potential of Hydrogen) Lots of H+ IONS Lots of OH- IONS Few to NO IONS
9 Acids þ Turns litmus paper RED þ Taste sour, Feel squeeky þ Corrode materials þ Conduct Electricity þ React with bases to form salts and water þ Measure 0-6 on the pH scale
10 Some Common Acids HCl hydrochloric acid (stomach) H 2 CO 3 carbonic acid (acid rain) H 3 PO 4 phosphoric acid (Coca Cola) H 2 SO 4 sulfuric acid (Batteries) CH 3 COOH acetic acid (Pickles)
11 Bases Turns Litmus Paper BLUE Taste bitter, chalky Feel soapy, slippery Also conduct electricity React with acids to form salts and water Measure 8-14 on the pH scale
12 Some Common Bases NaOHsodium hydroxide (DRANO) KOH potassium hydroxide (Tie Dye) Na 2 CO 3 sodium carbonate (baking soda) Mg(OH) 2 magnesium hydroxide (MOM) Al(OH) 3 aluminum hydroxide (TUMS)
ACTIVITY DIRECTIONS Observe: Which samples are acids & which are bases? Hypothesis: Discuss with your group. Experiment: Take a clean Qtip and insert it into the solution. Wipe it onto the paper. If it is a Base, it will turn the paper orange; if its an acid, it will erase the orange mark. Test all six substances. Conclusion: Which are acids & which are bases? 13