1. Substances, Mixtures, Solubility & Solutions Chapter 8!

2. Substances, Mixtures, Solubility & Solutions Objectives 1) Understand the different types of solutions that exist, and how solutions form. 2) Understand the different types of mixtures. 3) Be able to explain the difference and give examples of an acid and a base. 4) Understand and know how to use a pH scale. 5) Define and be able to explain certain vocabulary words. What is an atom = Small particle that makes up most types of matter –Same atoms of an element = same number of protons –IE – pencil “lead”…graphite = form of carbon What is a substance = matter that has the same fixed composition and properties. –Oxygen, Carbon, Nitrogen, water Can not be broken down by physical process –IE – boiling, grinding A chemical process is the only method to change a substance into more than one new substance. –Burning, reacting with other chemicals What is a solution = homogeneous mixture What is a compound = Atoms of two or more elements chemically combined –IE – Water = H 2 O

3. What is a Mixture = combinations of substances that can be separated by physical means –IE – water at the ocean – water and salt –Separate? boiling to separate water from salt Difference between a compound and a mixture? = compounds always have the same proportions of different substances, and mixtures don’t –IE – mixture of clothing…

4. 2 kinds of mixtures: 1)Heterogeneous mixture: “hetero” = different not mixed evenly easy to tell different parts of mixture IE – watermelon… IE – concrete… 2) Homogeneous mixture: “homo” = same composition is the same throughout usually not easy to tell parts of mixture apart IE – salt water… IE – milk… Another name for a homogeneous mixture is a solution

6. Copy onto piece of paper…then add four examples under each: Element, Compound, Homogeneous mixture, Heterogeneous mixture. Add pictures and color if you have time

7. Solutions: Forming Solutions –one substance disappears into the other Substance that disappears or dissolves = solute substance that dissolves the solute = solvent a solution usually contains more solvent than solute a substance that readily dissolves in another is soluble a substance that doesn’t readily dissolve is insoluble –IE – Salt H 2 0 »Solute? = »Solvent? =

8. Some substances can be combined (bonded) to fall out of a liquid as a solid = precipitate Soap scum that forms when minerals in water react with soap Concentration = how much solute is present when compared to the amount of solvent A concentrated solution has more solute present in a given amount of solvent. A dilute solution would not have as much solute in a given amount of solvent.

9. Types of solutions Solutions are more than just a solid (solute) in a liquid (solvent) Many kinds that can involve solids, liquids, and gases All around you, and inside you! Gaseous Solutions Small amount of one gas is dissolved in a larger amount of another gas IE – gas we breathe –Nitrogen = 78% of air –Others: Oxygen, CO 2, Ar, Ne, He, Krypton, H, Xe, & O 3 »Solvent = N »Solute = all others Liquid Solutions most familiar with = liquid solvent mixed with another liquid, solid, or gas Gas - Liquid solution –IE – Soda…CO 2, liquid Liquid – Liquid solution –IE – Vinegar…95% H 2 O, 5% Acetic Acid Solid Solutions solvent is a solid with a gas, liquid or solid most common solid – solid solution both solvent and solute are solids 2 or more metals = alloy Gas – liquid…freeze it…turns into a gas – solid IE – freezing can of soda

10. Universal solvent = H 2 O - H 2 O can dissolve many different solutes H 2 O is a polar molecule – has a slight charge on each end of the molecule – the positive and negative charges on each end pulls other molecules apart Solubility = describes how much solute will dissolve in a given amount of solvent –A solution that contains all of the solute that it can hold under given conditions = saturated solution Acids and Bases 1) Acids: substances that taste sour and produce positive hydrogen ions when dissolved in water and turns litmus paper red reacts with some metals and will leave holes… very corrosive IE – citric juice, vinegar, dill pickles >>> Never taste to find out…Why? acids can cause burns and damage body tissues… IE – carbonic acid dissolves calcium carbonate in limestone…drops form stalagmites and stalactites…air pollution causes acid rain and can eat away at stone… IE – ants inject formic acid to cause pain… IE – sulfuric acid is in auto batteries = battery acid IE – hydrochloric acid…your stomach!

11. 2) Bases: substances that taste bitter and produce negative hydroxide ions (OH - ) when dissolved in water and turns litmus paper blue - very corrosive but usually won’t hurt metals –IE – soap…taste bitter! –IE – can cause burns and damage body tissues –IE – hydroxide ions react with certain substances such as dirt and grease, so it is a good cleaning solution…IE = Ammonia –IE – antacid tablets, chalk… –IE – your blood is a basic solution… –IE – sodium hydroxide (NaOH), = lye = strong base used in cleaners pH: measure of how acidic or basic a solution is = “ power of hydrogen” pH scale: measures the strength of acids and bases –scale from 0 to 14 –lower numbers are acidic, and higher numbers are basic –number 7 is neutral –used to test pool water…safe for swimming…!

12. Neutralization = reaction that occurs between an acid and a base in which the properties of each one are cancelled out. IE – Hydrochloric acid in your stomach…too much will cause discomfort…What do you do? You take an antacid…gets rid of stomach ache… Antacid is a base that counteracts the acid. A strong acid reacting with a strong base will form a salt…(reaction on board…) Acid & Base Indicators: –lets you know if the compound is an acid or a base by the color 2 main indicators: 1) litmus paper = acid turns blue to red, base turns red to blue 2) phenolphthalein = acid is colorless, base turns bright pink