1/31/2014 What is pH? Which ion is in acids? Which ion is in bases?

Today’s Goal I CAN use physical and chemical changes to decide if a chemical reaction has taken place.

Today’s Plan Lab analysis pH reading & outline Lab Conclusion Chemical Reactions

Solutions of Acids and Bases

A. Strengths of Acids and Bases Concentration: the amount of acid or base dissolved in water Strength: the number of ions that will break apart when dissolved in water

1. Strong versus Weak Acids In a strong acid, almost all of the molecules break apart to form H+ In a weak acid, only some of the molecules break apart to form H+

2. Strong versus Weak Bases In a strong base, almost all molecules break apart to produce OH- In a weak base, only some of the molecules break apart to produce OH-

B. Acids, Bases, and Neutralization Neutralization reaction: the reaction of an acid and a base to form a neutral solution of water and a salt H+ and OH- come together to form H2O The other ions from the solution form a salt

Indicator: identifies whether a substance is an acid or base 1. The pH scale Indicator: identifies whether a substance is an acid or base Example: litmus paper, cabbage juice pH scale: measures of how how acidic or basic a solution is Neutral pH is 7 Acids are lower than 7 Bases are higher than 7

2. Using Indicators to Determine pH Indicators show an acid or base or the exact pH

3. pH and the Environment pH affects living things like plant growth Rain should have pH of 5.5-6, slightly acidic Pollution causes acid rain pH 3-4.5, which can kill plants and animals

C. Salts Salt: an ionic compound that forms when a metal atom replaces the hydrogen of an acid There are lots of other salts besides table salt (NaCl)

Now write a paragraph for your lab conclusion Now write a paragraph for your lab conclusion. Include the following information: What you did in the lab Which pH are acids? Which pH are bases? Why is it important to know whether something is acidic or basic?

Now that you can count atoms, you are ready to learn about chemical equations

As a group arrange the coins on your desk into four random piles. Count the value of each pile, then count the TOTAL value of the piles, and record it in your journals. Do this TWO more times! (Rearrange the piles and count) (Make sure ALL my change makes it back in the bag.)

Did rearranging the coins change any individual coin? Did rearranging the coins change the TOTAL value of the coins? If you think of the coins as representing different types of atoms, what does this model tell you about chemical reactions?

We use symbols when writing chemical reactions. Using these symbols makes it easier and faster to read and write reactions. How else do you use symbols as a short-cut in daily life?

Take 2 minutes to draw and color a symbol that you see or write often in your own life. It might be a road sign, a “text” word or phrase that has become a symbol, a sports team’s logo, etc.

A chemical equation is a shorter, easier way to show chemical reactions, using symbols instead of words. Get out your planners! Use the Periodic Table of the Elements in your planner (in the “Student Reference” section) to determine what each of these symbols stand for…

Au Pb Ag Sn Fe Al Ca C What do these symbols stand for? Record the symbol and what it stands for in your journal! Au Pb Ag Sn Fe Al Ca C

Au Pb Ag Sn Fe Al Ca C Gold Lead Silver Tin Iron Calcium Carbon Aluminum

You have already seen many chemical formulas… H2O What does the “H” stand for? What does the “O” stand for? What does the little “2” stand for?

Here are some familiar formulas: Compound Formula Aspirin C9H8O4 Bleach NaClO Sugar C12H22O11 Rust Fe2O3 Rubbing Alcohol C3H8O

Compound Formula Made of…. Aspirin C9H8O4 Carbon, Hydrogen, Oxygen Bleach NaClO Sodium, Chlorine, Oxygen Sugar C12H22O11 Rust Fe2O3 Iron, Oxygen Rubbing Alcohol C3H8O

Structure of a chemical equation: Every chemical equation is written THE SAME WAY… Reactant + Reactant  Product + Product Sometimes there are more than 2 reactants. Sometimes there is only 1 reactant. Sometimes there are more than 2 products. Sometimes there is only 1 product.

CaCO3 CaO + CO2 How many reactants are there? See if you can answer the following questions for this chemical reaction: CaCO3 CaO + CO2 (Heated) How many reactants are there? What is/are the reactant(s)? How many products are there? What is/are the product(s)?

CaCO3 CaO + CO2 * Notice that the atoms we began with are the same atoms we end with, just in a different order! (Heated) Ca C O O O 3 2

Think about our class. We have a group of students and a teacher.

When the bell rings, you all leave and a new group of students comes in, and all of you go to a new class room.

The number of students and teachers in the school has not changed The number of students and teachers in the school has not changed. But their arrangement is different and the new groups interact differently.

The amount of matter involved in a chemical reaction does not change. The total mass of the reactants MUST EQUAL the total mass of the products. We call this principle Conservation of Matter.

How do you know if the mass of the products is equal to the mass of the reactants? Subscript Numbers! If you add up the NUMBER of EACH element on the reactant side and compare it to the NUMBER of the SAME element on the product side you can tell if the mass of the reactants is equal to the mass of the products. CaCO3  CaO + CO2

Do this… Na + Cl  NaCl 1. Count up the number of Na and Cl atoms on the reactant side. Na = 1 Cl = 1 2. Count up the number of Na and Cl atoms on the product side. 3. Compare the numbers. Are they the same? If so then the mass of the reactants and the products is equal. Yes! The masses are equal!

Try this… Fe2 + S2  Fe2S2 1. Count up the number of Fe and S atoms on the reactant side. Fe = 2 S = 2 2. Count up the number of Fe and S atoms on the product side. 3. Compare the numbers. Are they the same? If so then the mass of the reactants and the products is equal. Yes! The masses are equal!

That makes this equation “unbalanced” Try this… H2 + O2  H2O 1. Count up the number of H and O atoms on the reactant side. H = 2 O = 2 2. Count up the number of H and O atoms on the product side. H = 2 O = 1 3. Compare the numbers. Are they the same? NO! The masses are NOT equal! That makes this equation “unbalanced”

That makes this equation “unbalanced” Try another one… CO2 + H2O  C6H12O6 + O2 1. Count up the number of C, H, and O atoms on the reactant side. C = 1 H = 2 O = 3 2. Count up the number of H and O atoms on the product side. C = 6 H = 12 O = 8 3. Compare the numbers. Are they the same? NO! The masses are NOT equal! That makes this equation “unbalanced”