Dissolving Solids, Liquids and Gases

2. Solubility POGIL Molarity POGIL Dissolving Solids, Liquids and Gases http://www.inquiryinaction.org/chemistryreview/dissolving/

4. Investigation 4: Dissolving Solids, Liquids and Gases Key concepts for students ● Dissolving applies to solids, liquids, and gases. ● Dissolving involves the interaction between the solvent and the solute. ● The extent to which a substance dissolves in a liquid is a characteristic property of that substance. ● Heat increases the solubility of most solids. ● Heat does not increase the solubility of all solids by the same amount. ● Heat decreases the solubility of most gases. Learning objectives Students will be able to: ● Identify and control variables to design and conduct valid experiments. ● Develop a definition of “dissolve” that applies to solids, liquids, and gases. ● Use observations and results of experiments to develop explanations to answer a question. ● Explain that the solubility of a substance depends on the characteristics of both the solute and the solvent giving each substance a unique solubility. ● Draw pictures and write captions showing the stages of a solid dissolving. ● Explain that heat affects the solubility of solids and gases differently.

5. Investigation 4: Dissolving Solids, Liquids and Gases Investigation questions Can solids, liquids, and gases all dissolve? ● How can you tell when a substance is dissolved? ● Does colored sugar dissolve equally well in water, vegetable oil, and alcohol? ● Does cocoa mix dissolve better in hot water or cold water? ● Do salt and sugar dissolve better in hot water than in cold water? ● Do all liquids dissolve in water? ● Can a gas dissolve in a liquid? ● Does temperature have an effect on how quickly dissolved gas escapes from a soda? ● How can you make a lemon soda that keeps as much carbonation as possible?

6. Dissolving - Summary • Solids, liquids, and gases can all dissolve. • Dissolving depends on the molecules of the substance doing the dissolving, • called the solvent, and the molecules of the substance being dissolved, • called the solute. • Dissolving is the process in which these molecules interact and attract each • other to form a solution. • The extent to which a substance dissolves is a characteristic property of that • substance called its solubility. • Water is a good dissolver because of its areas of positive and negative • charge. The mutual attraction between water molecules and other • substances with positive and negative charges causes these substances to • dissolve.

7. Chemical Change http://www.inquiryinaction.org/chemistryreview/chemical_change/ Acid/Base POGIL Calculating pH POGIL

8. Acid: A substance that releases H+ ions in an aqueous solution “aqueous” means: water

9. Characteristics of Acids: • Acids have a sour taste • Acids react with metals • Acids contain Hydrogen • Many are poisonous and corrosive to skin H

10. Strong Acids (break down completely to give off many H+ ions)

11. Weak Acids (only partially breaks down, gives less H+)

12. Acids and Bases Acids: Some common acids in our daily life: Ethanoic Acid, CH3COOH: found in vinegar, tomato juice Citric Acid, C6H8O7: found in citrus fruits Lactic Acid: found in sour milk, yogurt Tannic Acid: Found in tea Tartaric Acid: Found in grapes What about those commonly found in our lab? Hydrochloric acid, HCl Sulfuric Acid, H2SO4 Nitric Acid, HNO3 Which of these is found in batteries? Sulfuric Acid

13. Base: A substance that releases OH- ions in an aqueous solution

14. Characteristics of Bases: • Bases usually taste bitter • Bases feel slippery • Bases contain hydroxide ions • STRONG bases are also poisonous and corrosive to skin OH-

15. Common Bases: (Hydroxides of Group 1 and Group 2 Metals are STRONG) All others are WEAK

16. Some bases (VERY FEW) don’t have OH- Most commonly: ammonia NH3

17. Reactions between acids and bases When and acid and a base react with each other, the characteristic properties of both are destroyed. This is called neutralization.

18. Reactions between acids and bases General formula for acid base reaction: Acid + Base → Salt H2O + NOT JUST NaCl !! “Salt” means any ionic compound formed from an acid/base reaction Neutralization Reaction Animation

19. Neutralization HCl + NaOH → H2O + NaCl acid base water salt

20. Neutralization Another Example HNO3 + KOH → H2O + KNO3 K OH H NO3 acid base water salt

21. Indicators An indicator is a compound that will change color in the presence of an acid or base • Red Litmus-Turns blue in base • Blue Litmus-Turns red in acid • Universal indicator (pH paper) Used for the full pH range • Phenolphthalein-Turns pink in base

22. pH pH stands for “potential hydrogen” and is a measure of how many H+ ions there are in solution. The MORE H+ there are, the LOWER the pH will be. pH = - log [H+]

23. pH Scale Shows the range of H+ concentrations High H+ concentration Low H+ concentration Virtual demonstration - Detecting acid/base

25. Investigation 5: Chemical Change Key concepts for students ● Substances react chemically in characteristic ways. ● Evidence that a chemical reaction has occurred includes: production of a gas, change in temperature, color change, and formation of a precipitate. ● A chemical reaction can be controlled by adjusting the amount of reactants. ● A chemical reaction can result in an increase in temperature (exothermic) or a decrease in temperature (endothermic). ● The color change of an acid–base indicator can help classify a solution as an acid or a base, identify when a solution has been neutralized, and compare the amount of acid or base in a solution. ● In a chemical reaction, the bonds holding one atom to another are broken, atoms rearrange, and then combine in new ways to create one or more different substances. ● In a chemical reaction, the atoms that make up the reactants are never destroyed or disappear. They rearrange and bond in new ways to form the products. Learning objectives Students will be able to: ● Design a testing procedure to compare the chemical reactions of different substances. ● Use the characteristic chemical reactions to identify an unknown substance. ● Recognize that production of a gas, change in temperature, color change, and formation of a precipitate are evidence of chemical change. ● Use a thermometer and graduated cylinder accurately. ● Control chemical reactions by adjusting the amount of the reactants. ● Use the color changes of an acid-base indicator to classify and compare different substances. ● Determine whether a new substance is created during a chemical reaction.

26. Investigation 5: Chemical Change Investigation questions ● Do powders that look the same have the same chemical reactions? ● How can you use the characteristic ways substances react to tell similar-looking substances apart? ● How can you identify an unknown powder? ● What are the active ingredients in baking powder? ● Aside from bubbling, what else happens during a reaction between baking soda and vinegar? ● How can you control the amount of gas produced in a baking soda-and-vinegar reaction? ● Can the temperature increase during a chemical reaction? ● How can you tell if a substance is an acid, a base, or neutral? ● How can you return the color of a red cabbage indicator solution back to blue? ● How can neutralizing acids help you compare the amount of acid in different solutions? ● What happens when soap is added to hard water?

27. Chemical Change - Summary • A chemical reaction happens when one or more substances change into entirely new substances with different properties. • The clues of a chemical reaction are production of a gas, change in temperature, color change, production of a precipitate. • In a chemical reaction, it takes energy to break the bonds in the reactants and energy is released when bonds are formed in the products. • If more energy is required to break the bonds than is released when new bonds are formed, the reaction is endothermic.