recipes start with a 2 cans of tomatoes, 2 cans of kidney beans, a tablespoon of chili powder or...
TRANSCRIPT
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 hrYield 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!
heat2C8H18 (l) + 25O2 (g) 16CO2 (g) + 18H2O (g) + energy
LEFT ARROW RIGHTReactant(s) Produce/yield/etc. Product(s)
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
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 changeThese 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 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!
