1. Init <<5/12/2008 by Daniel R. Barnes WARNING: This presentation includes a combination of original graphical images created by the author and images taken without specific permission from the world wide web. Do not distribute or copy this presentation. CAUTION: This author uses Wikipedia as though it could be trusted. Uh-BUGGA-BUGGA-BUGGA-BUGGA-BOO!

2. I looked, but I saw nothing in the NGSS that specifically stated that high school students needed to learn general princples about acids and bases. Gulp™?

3. SWBAT...... list the observable properties of acids, bases, and salt solutions.

4. No, wait, I’m not the corrosive & irritating one. ACIDS and BASES are corrosive and irritating. Okay, well, maybe I am irritating, but I’m not corrosive. Just remember to wear your goggles during labs, okay? And NO CONTACT LENSES on lab days!

5. How long are you supposed to wash your eyes out if you get acids or bases or anything else in them? According to the Flinn Scientific Student Safety Contract that you should have signed by now...

6. Too bad we don’t have a second pair of hands on our faces like this. If we did, we could use our regular hands to keep the eyewash handle turned on. Since we don’t have face hands, you’ll need a buddy to keep the eyewash fountains turned on while you hold your eyes wide open with your fingers.

7. “When acid comes into contact with the body it feels like water. It wets the body and a burning sensation begins that gradually increases in intensity. The patients cry in agony until the chemical is washed away or is neutralized. The affected skin becomes black and leather-like. The chemical also leaves its mark on the healthy skin it trickles over”

8. http://www.enotes.com/topic/Chemical_burn sodium hydroxide burn Alkali burn http://www.burnsurgery.org/Betaweb/Modules/initial/part_two/sec6.htm

9. Acid “cooks” flesh.

10. BASE ACID

11. Bases taste bitter. Acids taste sour.

12. Acids, bases, and salts are all electrolytes, although some are strong and some are weak. electrolyte pure water (a non-electrolyte) + - + - - + - + - + (has freely wandering ions) = ? + - + -

13. Acids react with metals, corroding the metals to form salt and hydrogen gas. Acid + metal  Salt + hydrogen gas Acids are typically stored in glass or plastic containers. You’ll probably never see an acid stored in a metal container. http://www.hbscc.nl/publications/23%20alkaline/alkaline2.htm Bases can corrode metal too:

14. Acids are more famous for being metal- destroyers, but bases are known for attacking metal in some cases, also. http://www.youtube.com/watch?v=WnPrtYUKke8 &feature=youtube_gdata_player Thank you, Roberto Pinzon, for giving me this link.

15. HS-PS-2. Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.

16. METAL HYDROXIDES tend to be BASES. Alakali metals react with water to form metal hydroxides. 2Na + 2H 2 O  H 2 + 2NaOH 2Li + 2H 2 O  H 2 + 2LiOH 2K + 2H 2 O  H 2 + 2KOH 2Rb + 2H 2 O  H 2 + 2RbOH 2Cs + 2H 2 O  H 2 + 2CsOH 2Fr + 2H 2 O  H 2 + 2FrOH (?) Q: What is the formula of the hydroxide ion? A: OH - Q: Why do alkali metals form hydroxides? A: Alkali metals have one valence electron, so they like to lose it to empty their outer shell, rendering them positive, which attracts them to negative ions like hydroxide.

17. ACID + BASE  SALT + WATER (usually) HCl + NaOH  NaCl + H 2 O Acid burn alkali burn fun at the beach!

18. Q: How do acids and bases taste? A: Acids taste sour. Bases taste bitter. Q: Acids and bases may be opposites, but what do they have in common? A: They are both corrosive and irritating. They are both electrolytes. Q: Why is red the symbolic color for acids and blue the symbolic color for bases in this presentation? A: Acids turn litmus paper red and bases turn it blue. Q: What is produced when an acid reacts with a base? A: Salt and water. Q: What is produced when an acid reacts with a metal? A: Salt and hydrogen gas.

19. SWBAT...... Define acids and bases in terms of ion donation and acceptance.

20. Acid: a substance that gives off H + ions in water. Base: a substance that gives off OH - ions in water. Svante Arrhenius 1859-1927 H+H+ OH - H + = “hydrogen ion” OH - = “hydroxide ion” HCl  H + + Cl - NaOH  Na + + OH -

21. + H Hydrogen 1 1.01 H + When it had an electron, it was a hydrogen atom Now that it’s lost its electron, it has become a hydrogen ion. All that’s left is just a single, lonely...... proton.

22. + H Hydrogen 1 1.01 H + = proton

23. Acid: a substance that gives off H + ions in water. Base: a substance that gives off OH - ions in water. H+H+ OH - H2OH2O Looking at these definitions of “acid” and “base”, one gets the idea that water is “normal”, “neutral”, and “average”, that it is the “middle chemical”. However, I have a nagging feeling that aliens from other planets may not share our view...

24. My drink’s getting a little low. You got anything to top it off with? No. God no! Are you trying to poison me? Now you’re talking!

25. Johannes Bronsted Thomas Lowry Acids donate hydrogen ions. Bases accept hydrogen ions. NH 3 is a base, but where’s the OH? NH 3 doesn’t give OH -, but it does take H +. Speaking of ammonia... NH 3 + H 2 O  NH 4 + + OH -

26. Honors students, you are required to learn about Lewis acids and Lewis bases on your own (to the degree that we fail to cover it in class).

27. Q: According to Svante Arrhenius, what is the definition of an acid? A: An acid is a chemical that gives off H + ions in water. Q: What was his definition of a base? A: Arrhenius said a base was a chemical that gave off OH - ions in water. Q: What is the Bronsted-Lowry definition of acids and bases? A: Acids give H + ions. Bases take H + ions.

28. SWBAT...... Explain how the self-ionization of water relates to K w

29. If this is a non-honors chemistry section, or if you’re simply pressed for time, please skip to pH. Honors students are required to learn about K w on their own even if there’s no time in class.skip to pH

30. Our notions of (at least the older definitions of “acid” and “base”) are prejudiced by the fact that Earth is a mostly water - covered planet and, that, consequently, Earth’s creatures, including people, are made mostly of water.

31. H2OH2O H+H+ + OH - Water molecules are very stable. Nonetheless, every once in a while, a water molecule breaks in two. The hydrogen and hydroxide ions that water breaks into like each other a lot because of their opposite charges, so they get back together again pretty fast. Therefore, the equation for the dissociation of water deserves a double arrow, since it is a reversible reaction.

32. H2OH2O H+H+ + OH - > 99.9% << 1% Because water molecules rarely break, and because they get back together again so quickly when they do break, the amount of broken molecules in a quantity of pure water is very low. The percentages listed here are quite rough. We can be even more precise if we want to.

33. H2OH2O H+H+ + OH - > 99.9% << 1% Because water molecules rarely break, and because they get back together again so quickly when they do dissociate, the amount of broken molecules in a quantity of pure water is very low. The percentages listed here are quite rough. We can be even more precise if we want to.

34. In pure water, the concentration of broken water molecules is 10 -7 M H+H+ + OH - That’s the same thing as 10 -7 mol/L 10 -7 mol/L = 0.0000001 mol/L One liter (L) of water has a mass of 1000 g. The molar mass of water is 18 g/mol. (1000 g)/(18 g/mol) = 55.6 mol, so the concentration of water in water is 55.6 mol/L. (55.6 mol/L)/(10 -7 mol/L) = 556,000,000 In pure water, only one out of every 556,000,000 water molecules is broken.

35. H+H+ + OH - In pure water, only one out of every 556,000,000 water molecules is broken. That’s about 0.002 ppm

37. H2OH2O H+H+ + OH - H 2 O + H 2 O H3O+H3O+ + OH -

38. H2OH2O H+H+ + Equilibrium: when opposite processes occur at equal rates. Amounts of different chemicals are probably not equal to each other. However, at equilibrium, the amount of each chemical does not change as time goes by. Unless disturbed, aqueous (watery) systems, such as a cup of water, an ocean, a car battery, or your bloodstream, will tend reach a state of equilibrium, in which the forward and reverse reactions shown below occur at equal rates. At equilibrium, water molecules fall apart but they come back together again just as quickly as they fall apart.

39. H2OH2O H+H+ + OH - LeChatelier’s Principle If a system is at equilibrium, the amount of each chemical will remain constant as time goes by. However, if a system at equilibrium is disturbed by some kind of stress, the reaction rates will change in whatever way will oppose the effects of the disturbance. If a bunch of molecules are at equilibrium and you disturb them, the molecules will try to undo the work you have done.

40. H2OH2O H+H+ + OH - LeChatelier’s Principle Imagine a bathtub full of water. If not disturbed, it will reach an equilibrium with regard to the above reversible reaction. H + = 3OH - = 3

41. H2OH2O H+H+ + OH - LeChatelier’s Principle However, if you raise the [H+], say, by pouring in some hydrochloric acid, this will disturb the equilibrium. H + = 3OH - = 3 Oh no you di-ent just add more H+! Didn’t you see us being in equilibrium? RUDE! Sa-kurity! 6

42. H2OH2O H+H+ + OH - LeChatelier’s Principle The system will now do whatever it takes to lower the [H + ], to undo what you just did... at least partially... H + = 3OH - = 36

43. H2OH2O H+H+ + OH - LeChatelier’s Principle The equilibrium, as they say, will “shift to the left”. Why? The forward reaction creates H+, but the reverse reaction (going to the left) uses up H+, turning it into water. H + = 3OH - = 364 1 Did you notice that by adding H+, you made OH- decrease?

44. It is generally true that if you make [H + ] increase, you will cause a decrease in [OH - ]. This is expressed mathematically by the following equation: [H + ][OH - ] = 10 -14 M 2 If two numbers always multiply to give the same result, then when one of the two numbers gets bigger, the other must get smaller. Take the following example: 1 x 24 = 24 2 x 12 = 24 3 x 8 = 24 4 x 6 = 24 6 x 4 = 24

45. It is generally true that if you make [H + ] increase, you will cause a decrease in [OH - ]. This is expressed mathematically by the following equation: [H + ][OH - ] = 10 -14 M 2 Now try some acid-base examples. These examples could be any aqueous (watery) system. If [H+] = 10 -3 M, then [OH-] = 10 -11 M If [H+] = 10 -12 M, then [OH-] = 10 -2 M If [H+] = 10 -1 M, then [OH-] = 10 -13 M If [H+] = 10 -7 M, then [OH-] = 10 -7 M If [H+] = 1M, then [OH-] = 10 -14 M 1 x 24 = 24 2 x 12 = 24 3 x 8 = 24 4 x 6 = 24 6 x 4 = 24

46. SWBAT...... use the pH system to characterize acid, base, and salt solutions.

47. 0 14 7 + -

50. Click the link below to an FDA web page listing pH’s of different foods. According to this web page, what is the overwhelming tendency for the pH of foods? Foods tend to be... http://www.engineeringtoolbox.com/ food-ph-d_403.html

52. “pH” stands for “potential hydrogen”. (maybe) pH is a weird, numerical way of showing the hydrogen ion concentration in a solution. Mathematically, pH = -log[H + ] That’s slightly confusing even if you know what logs are.... the esoteric version...

53. log(1000) = 3 log(10) = 1 log(1,000,000) = 6 log(100) = 2 log(50) = 1.6987... log(0.1) = -1 log(1) = 0 log(0.0001) = - 4 log(10 13 ) = 13 log(10 -5 ) = -5 log(10 n ) = n

54. Let’s give an example of pH: normal water. In normal water, the hydrogen ion concentration is 10 -7 M. In other words, [H + ] = 10 -7 M. Since pH = -log[H + ]... The pH of normal water would be 7.

55. In sea water, however, the pH is 8. What would the hydrogen ion concentration be in sea water? In sea water, [H + ] = 10 -8 M. That’s a little more basic than pure water.

56. Car batteries are filled with very dangerous sulfuric acid. In battery acid, one of the most corrosive acids there is, the hydrogen ion concentration is about 1M. H 2 SO 4 In battery acid, the pH is...0 1 = 10 0, so...

57. Lemon juice is one of the most acidic foods you can eat. In lemon juice, the hydrogen ion concentration is about 10 -2 M. In lemon juice, the pH is... 2 That’s not as strong as battery acid, but it can still rot your teeth.

58. Sodium hydroxide is a strong base. In a concentrated sodium hydroxide solution, the hydrogen ion concentration can be about 10 -14 M. In such a concentrated solution of sodium hydroxide, the pH is... 14 It’s also known as “lye” and turns fat into soap, which makes it a handy drain opener.

59. A typical pH for vinegar is 3. What would the hydrogen ion concentration be in vinegar? In vinegar, [H + ] = 10 -3 M. That’s not quite as acidic as lemon juice or battery acid, but that’s still pretty sour.

60. H+H+ High [H + ] Low pH Low [H + ] High pH

61. OH - High [OH - ] Low pOH Low [OH - ] High pOH

62. It is generally true that if you make [H + ] increase, you will cause a decrease in [OH - ]. This is expressed mathematically by the following equation: [H + ][OH - ] = 10 -14 M 2 Now, just for fun and review, tell me the pH for each of the following solutions, and tell me if it’s acid, base, or neutral. If [H+] = 10 -3 M, then [OH-] = 10 -11 M If [H+] = 10 -12 M, then [OH-] = 10 -2 M If [H+] = 10 -1 M, then [OH-] = 10 -13 M If [H+] = 10 -7 M, then [OH-] = 10 -7 M If [H+] = 1M, then [OH-] = 10 -14 M pH = 3 (acid) pH = 12 (base) pH = 1 (acid) pH = 7 (neutral) pH = 0 (acid)

63. If the pH of a concentrated sodium hydroxide solution is 14, Then the pOH is... Low pH = acid (<< 7) pH + pOH = 14 pH of 7 = neutral (like water) High pH = base (>7) zero High pOH Medium pOH Low pOH

64. H+H+ OH - H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ High [H + ] or low [H + ]? High [OH - ] or low [OH - ]? High pH or low pH? High pOH or low pOH? Acid, base or neutral? Example #1

65. OH - H+H+ H+H+ H+H+ H+H+ High [H + ] or low [H + ]? High [OH - ] or low [OH - ]? High pH or low pH? High pOH or low pOH? Acid, base or neutral? OH - Example #2

66. OH - H+H+ H+H+ H+H+ H+H+ High [H + ] or low [H + ]? High [OH - ] or low [OH - ]? High pH or low pH? High pOH or low pOH? Acid, base or neutral? OH - H+H+ medium = 7 medium = 7 Example #3

67. Q: What is the mathematical definition of pH? A: pH is -1 times the log of hydrogen ion concentration. In other words, pH = -log[H + ] Q: What kinds of materials have what kinds of pH’s? A: Acids have pH’s less than 7, bases higher than 7, neutral materials (like pure water) equal to 7. Q: What is the relationship between pH and pOH? A: pH + pOH = 14; low pH means high pOH & vice versa. Q: What is “[H + ]”? A: [H + ] = hydrogen ion concentration, in mol/L Q: What kinds of pH’s do you get when [H + ] is low and when [H + ] is high? A: Low [H + ]  high pH. High [H + ]  low pH.

68. SWBAT...... define what “strong” and “weak” mean when used to describe acids and bases.

69. Cl H + - H + - H + - H + - H + - H + - H + - Every single HCl molecule that enters the water splits up into ions. Therefore, HCl is considered to be a “strong” acid.

70. - + H O C O C H H H H O C O C H H H H O C O C H H H H O C O C H H H H O C O C H H H Only some of the CH 3 COOH molecules split into ions. In fact, most of them did not. CH 3 COOH is a “weak acid”.

71. STRONG ACIDS: WEAK ACIDS: HCl HBr HI HF anything with COOH H 2 SO 4 HNO 3 HClO 4 all other acids HF + H 2 O  F - + H 3 O +

72. CH 3 COOH HOOC–CH 2 –COH(COOH)–CH 2 –COOH H 2 SO 4 HNO 3 NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 CH 3 (CH 2 ) 16 COONa hydrochloric acid HCl

73. HOOC–CH 2 –COH(COOH)–CH 2 –COOH HCl H 2 SO 4 HNO 3 NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 CH 3 (CH 2 ) 16 COONa acetic acid CH 3 COOH “monoprotic” 5% 85%

74. HCl H 2 SO 4 HNO 3 CH 3 COOH NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 HOOC–CH 2 –COH(COOH)–CH 2 –COOH CH 3 (CH 2 ) 16 COONa

75. HOOC–CH 2 –COH(COOH)–CH 2 –COOH HCl HNO 3 CH 3 COOH NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 CH 3 (CH 2 ) 16 COONa H 2 SO 4 hydronium ion H3O+H3O+ “weak” diprotic “STRONG” sulfuric acid http://www.youtube.com/watch?v=100Bk580mPY&feature =youtube_gdata_player

76. HOOC–CH 2 –COH(COOH)–CH 2 –COOH HCl H 2 SO 4 HNO 3 CH 3 COOH NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 CH 3 (CH 2 ) 16 COONa phosphoric acid Don’t be fooled by the H 3.H 3 PO 4 is a strong molecule, so it is a “weak” acid. H 3 PO 4 may be “triprotic”, but none of the H’s come off easily.

77. methyl group carboxylic acid group acetic acid C2H4O2C2H4O2 CH 3 COOH formula? ethanoic acid

78. HCl CH 3 COOH HOOC–CH 2 –COH(COOH)–CH 2 –COOH H 2 SO 4 NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 CH 3 (CH 2 ) 16 COONa nitric acid HNO 3

79. HCl CH 3 COOH HOOC–CH 2 –COH(COOH)–CH 2 –COOH H 2 SO 4 NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 CH 3 (CH 2 ) 16 COONa nitric acid HNO 3 Abu Musa Jābir ibn Hayyān 721-815 AD

80. HCl H 2 SO 4 HNO 3 CH 3 COOH NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 CH 3 (CH 2 ) 16 COONa citric acid HOOC–CH 2 –COH(COOH)–CH 2 –COOH H H H H H H H H O O O O O O O C C C C C C ? ? ?

82. CH 3 (CH 2 ) 16 COONa HNO 3 HCl CH 3 COOH HOOC–CH 2 –COH(COOH)–CH 2 –COOH H 2 SO 4 KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 sodium hydroxide NaOH Metal hydroxides are generally bases. Group 1A & 2A metals are especially famous for reacting with water to form alkaline solutions.

83. NaOH HNO 3 HCl CH 3 COOH HOOC–CH 2 –COH(COOH)–CH 2 –COOH H 2 SO 4 KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 sodium stearate + CH 3 (CH 2 ) 16 COONa

84. NaHCO 3 CH 3 (CH 2 ) 16 COONa NaOH HNO 3 HCl CH 3 COOH HOOC–CH 2 –COH(COOH)–CH 2 –COOH H 2 SO 4 KOH Ca(OH) 2 H 3 PO 4 ammonia NH 3

85. NH 3 is a base. According to Arrhenius, though, it can’t be a base. Why? It has no OH to give off. But all experimental evidence shows that ammonia is a base. ???!!! NH 3 + H 2 O  NH 4 + + OH - NH 3 is a gas when pure, but, it dissolves in water very readily. When it does, some of the ammonia molecules even steal protons from water! Stealing protons is the opposite of giving protons, so ammonia is the opposite of an acid. Ammonia is a base. Ammonia is a weak base.

86. Johannes Bronsted Thomas Lowry Acids donate hydrogen ions. Bases accept hydrogen ions.

87. NaHCO 3 CH 3 (CH 2 ) 16 COONa NaOH HNO 3 HCl CH 3 COOH HOOC–CH 2 –COH(COOH)–CH 2 –COOH H 2 SO 4 KOH Ca(OH) 2 H 3 PO 4 ammonia NH 3 ammonium hydroxide NH 4 OH

88. HCl H 2 SO 4 HNO 3 CH 3 COOH NaOH KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH NaHCO 3 HOOC–CH 2 –COH(COOH)–CH 2 –COOH CH 3 (CH 2 ) 16 COONa

89. Q: What is the difference between a monoprotic acid, a diprotic acid, and a triprotic acid? A: A monoprotic acid has one H + to give away. A diprotic acid has two H + ’s to give away. A triprotic acid has three. Q: When you see “COOH” in a formula, what does this indicate? A: The chemical is a weak acid. Q: What is the difference between a strong acid and a weak acid? A: Strong acids completely dissociate in water. Weak acids do not. (Same thing for strong vs weak bases.) Q: How many strong acids are there? Name them. A: Six: HCl, HBr, HI, H 2 SO 4, HNO 3, HClO 4.

90. SWBAT...... Predict and explain the outcome of acid-base neutralization reactions.

91. CH 3 (CH 2 ) 16 COONa NaOH HNO 3 HCl CH 3 COOH HOOC–CH 2 –COH(COOH)–CH 2 –COOH H 2 SO 4 KOH Ca(OH) 2 H 3 PO 4 NH 3 NH 4 OH sodium hydrogen carbonate NaHCO 3 + +CH 3 COOHNaCH 3 COO + CO 2 + H 2 O BASE ACID SALT WATER

92. Acids and bases neutralize each other, turning into salt and water in the process. HCl + NaOH  NaCl + H 2 O HCl + KOH  KCl + H 2 O HBr + CsOH  CsBr + H 2 O H 2 SO 4 + Cu(OH) 2  CuSO 4 + 2H 2 O CH 3 COOH + NaOH  NaCH 3 COO + H 2 O CH 3 COOH + RbOH  RbCH 3 COO + H 2 O H 2 CO 3 + 2LiOH  LiHCO 3 + LiOH + H 2 O  Li 2 CO 3 + 2H 2 O H 2 CO 3 + Ca(OH) 2  CaCO 3 + 2H 2 O H 2 SO 4 + Mg(OH) 2  MgSO 4 + 2H 2 O

93. Acids and bases neutralize each other, turning into salt and water. HCl + NaOH  NaCl + H 2 O HCl + KOH  KCl + H 2 O HBr + CsOH  CsBr + H 2 O H 2 SO 4 + Cu(OH) 2  CuSO 4 + 2H 2 O CH 3 COOH + NaOH  NaCH 3 COO + H 2 O CH 3 COOH + RbOH  RbCH 3 COO + H 2 O H 2 CO 3 + 2LiOH  LiHCO 3 + LiOH + H 2 O  Li 2 CO 3 + 2H 2 O H 2 CO 3 + Ca(OH) 2  CaCO 3 + 2H 2 O H 2 SO 4 + Mg(OH) 2  MgSO 4 + 2H 2 O ACID BASE SALTWATER ACID BASE SALTWATER ACID BASE SALT WATER ACID BASE SALT WATER ACID BASE SALT WATER ACID BASE SALT WATER ACID BASE SALT WATER ACID BASE SALT WATER ACID BASE SALT WATER

94. SWBAT...... recall that proteins are polymers made of amino acid monomers.

95. amino acid amino acid amino acid amino acid amino acid amino acid amino acid amino acid amino acid amino acid amino acid amino acid Protein is a polymer made of amino acid monomers.

96. amino acid amino acid H+H+ - An amino acid can neutralize itself. It’s part acid, part base. The name “amino acid” is kind of misleading. “Amino” refers to ammonia. Ammonia = NH 3. “Amino acid” sort of means “base acid”. Ammonia is a base.

97. We’ll learn more about amino acids in our next unit...... ORGANIC CHEMISTRY. Until then...

98. Okay, now it’s probably time to * Turn in the Chapter 19 Packet. * Take the Ch 19 Quiz Next meeting, there may be a lab. Dress for lab next meeting. (No contact lenses, no sandals, etc..)

99. B’dee-uh b’dee-uh b’dee-uh That’s all folks!