Classic Chem It’s the acid test 9-12 Science Std: Chem 5a

We started with: Solutions A solution is: A homogeneous mixture Of 2 or more substances In a single phase

We then looked at : Chemical Equations NaCl + AgNO 3 The reactants An equation shows: AgCl + Na + + NO 3 - And the products It can show how much is there and if there are ions or whole compounds

And yesterday we covered What is an acid and a base An acid is: A compound that increases the concentration of hydrogen ions in a water solution A base is: A compound that increases the concentration of hydroxide ions in a water solution H+H+ OH -

And yesterday we covered And the pH scale The scale goes from Between 1 and 7 is acidic And the center of the scale is a And between 7 and 14 is basic And a pH of 7 is neutral

Now its time to look at : How you can tell it is an acid You can use a pH meter To read the pH and tell if it is an acid or a base But there are other ways to tell….

Now its time to look at : How you can tell it is an acid There are 5 ways to tell something is an acid So let’s look at them

What is an acid? The first property: Acids mixed in water have a sour taste But you shouldn’t taste everything to see if it is an acid Let’s see why

Why not? First of all….. If the acid is concentrated If the pH is really low The acid can eat up your mouth 1 7

Why not? Next…. A lot of acids Are poisons So they can kill you if you eat enough

Why not? But there are some acids you can taste… Citric Acid This gives some fruit their tangy taste So a sour taste is a sign that it is an acid

What is an acid? The second property: Acids change the color of acid/base indicators You may have used litmus paper before to test things And see if something is an acid

What is an acid? The second property: We will use one of these other things to make our own pH indicator But more on this when we do the lab….

What is an acid? The second property: But there are other things that can change color Hydrangeas can change color with soil acidity And there are lots of other things that work too

What is an acid? The third property: Some acids react with metals to release a gas Depending on the type of acid And the type of metal You can make different gasses

What is an acid? The third property: Here are some different types: Sulfuric Acid makes hydrogen gas (flammable) Nitric acid makes nitrous oxide gas (poison) Movie

What is an acid? The third property: Smog mixes with water vapor and makes sulfuric acid This mixes with rain water And becomes acid rain Which can dissolve metal and stone

What is an acid? The fourth property: Acids react with bases to make salts and water These salts are different than you think So let’s make this clear

What is an acid? The fourth property: A salt is any ionic compound That comes from neutralizing an acid with a base Example: HCl and NaOH Make NaCl

What is an acid? The fourth property: A salt is any ionic compound That comes from neutralizing an acid with a base Example: H 2 SO 4 and CuO Make CuSO 4

What is an acid? The fourth property: Other salts include Sodium carbonate Zinc sulfide Ammonium Nitrate Used to make soap To make glass and lenses To make fertilizer

What is an acid? The fourth property: We talked about making water…. An acid adds hydrogen Ions A base adds hydroxide ions Add them together…. H+H+ And you get water OH - H2OH2O

What is an acid? The fifth property: Some acids conduct electricity This means you can put 2 wires in an acid solution And pass an electrical current through it

What is an acid? The fifth property: How does this work? When you put some acids in water Like HCl acid They break apart into ions in solution HCl

What is an acid? The fifth property: The ions have electric charge And these charges are floating around The anions have a spare electron attached ready to move HCl + -

What is an acid? The fifth property: The electrons in a current Pass from ion to ion in the solution So the solution is like a wire HCl + -

And that’s the list Review the 5 Acid Tests 1.Acids in water have a sour taste 2. Change the color of pH indicators 3. React with metals to release gas 4. React with bases to make water and salts 5. Some acids conduct electricity

Your Homework….. Quiz Retake is due today Otherwise No homework just yet.