RECIPES Start with a 2 cans of tomatoes, 2 cans of kidney beans, a tablespoon of chili powder or more to suit your tastes, salt, pepper, a chopped onion, 1 pound of ground beef. Brown meat in a pot, drain fat, add chopped onion. Open the beans and drain them. Open the tomatoes. Add tomatoes, beans, chili powder, salt and pepper to the beef. Heat to boiling. Simmer with a lid on for 1 hour. This recipe makes enough chili for 6 servings of chili. Ingredients, form, amount, conditions, time, product You can say it in lots of words or in shorter recipe form.

RECIPES 2 cans tomatoes 2 cans kidney beans , drained 1 tbsp chili powder (or more) Salt Pepper 1 chopped onion 1 pound of ground beef, browned and drained. Combine ingredients and simmer 1 hr Yield 6 servings

Chemical Equations = Chemical Texting HI BEST FRIEND, WHAT’S UP? I LOVE CHEMISTRY. CHEMISTRY IS GREAT! (LAUGH OUT LOUD) GOT TO GO SEE YOU LATER! How few characters can you use to express the truths shown above?

CHEMICAL REACTION A well-defined example of a chemical change One or more substances rearrange atoms to produce one or more different substances Expressed in several forms Words Word equations Formula or chemical equations

What makes your car go? Liquid octane and oxygen gas react with heat to produce carbon dioxide gas, water vapor, and energy.

What makes your car go? Liquid octane and oxygen gas react to produce carbon dioxide gas, water vapor, and energy. Less writing and more info in a chemical equation! heat 2C8H18 (l) + 25O2 (g)  16CO2 (g) + 18H2O (g) + energy LEFT ARROW RIGHT Reactant(s) Produce/yield/etc. Product(s)

COEFFICIENTS show ratio of substances 2C8H18 (l) + 25O2 (g)  16CO2 (g) + 18H2O (g) + energy COEFFICIENTS show ratio of substances ENERGY and other conditions may also be shown SUBSCRIPTS show other descriptive information

Other symbols + plus or reacts with SUBSCRIPTS (s) or (cr) solid or crystalline (g) gas (l) liquid (aq) aqueous or dissolved in water…this is NOT the same as liquid

Other symbols gas precipitate (solid forming from solutions) reaction goes both ways, forward and reverse

Over the arrow REACTION CONDITIONS may be shown over the arrow Heat a triangle also stands for heat D Light Electricity Catalyst (such as Pt) Pt (note: a catalyst make a reaction happen more quickly without itself being changed in the reaction) Temperature, pressure, time, etc. may also be shown over the arrow.

Indications of a Chemical Reaction Heat and light Production of a gas Formation of a precipitate Color change These easily observed changes indicate that a chemical reaction may have taken place. Absolute proof is provided by chemical analysis of the products.

Characteristics of a Chemical Equation Represents the known facts Contains the correct formulas of reactants and products The Law of Conservation of Mass is followed both in number of atoms and masses

Rules for Balancing Chemical Equations: A balanced chemical equation will obey the Law of Conservation of Mass. There will be an equal number of atoms of each element on either side of the equation.

EXAMPLE: Hydrogen gas reacts with oxygen gas to produce water vapor (or gas). 2H2 (g) + O2 (g)  2H2O (g) REACTANTS: PRODUCT: H= 4 atoms H = 4 atoms O = 2 atoms O = 2 atoms

Write the correct formula for all reactants and products. (Don’t forget BrINClHOF for diatomic elements. There are also polyatomic elements such as S8.) Do not change the subscripts in compounds once the correct formulas are written.

Tally the atoms or polyatomic ions on each side of the equation in a format that can be revised. Revise the tally with each change. Use coefficients in front of the elements and compounds to balance the number of atoms of each element. RIGHT: 2NaNO3 WRONG: Na2NO3

Balance different atoms one at a time. Balance combined elements first Balance different atoms one at a time. Balance combined elements first. Balance oxygen and hydrogen last. Balance polyatomic groups together as a unit when they exist on both sides of the equation. Sometimes it is easier to balance water as HOH instead of H2O (if OH1- ion is involved).

Reduce the coefficients to the lowest whole number ratio. RIGHT: 2H2 (g) + O2 (g)  2H2O (g) WRONG: 4H2 (g) + 2O2 (g)  4H2O (g)

If you get stuck, quit, take a break, and start over with a fresh perspective. If you still can’t solve it, start over and try putting a 2 in front of the most complicated reactant, and if that fails, try a 3. Eventually, you’ll get it!