Ch 21 Chemical Changes Bellwork: In your Science Notebook, define the following terms: Chemical reaction Reactant Product Chemical equation Coefficient Balanced Chemical Equations

Ch 21 Chemical Changes CLE 3202.1.4 Investigate chemical and physical changes. CLE 3202.1.9 Apply the Laws of Conservation of Mass/Energy to balance chemical equations.

What are we going to learn today? I CAN: Identify reactants and products of a chemical reaction. I CAN: Determine how a chemical reaction satisfies the law of conservation of mass. I CAN: Determine how chemists express chemical changes using equations.

What do we already know? List three examples of chemical reactions: One unique observation per pair. (How do chemical changes differ from physical changes?) Definition of equation: A statement of the equality or equivalence of mathematical or logical quantities Law of Conservation of Mass…in a chemical reaction, matter is neither created nor destroyed.

Describing Chemical Reactions a change in which one or more substances are converted into new substances Reactant: the substances that react Products: the new substances produced

Writing Equations Reactants --------Yield-------------- Products - + (aq) Heat, light, electricity

Antoine Lavoisier Father of Modern Chemistry Chemistry textbook Chemical nomenclature IUPAC Conservation of Mass Pg 632 Mass of candles and oxygen before burning is exactly equal to mass of remaining candle and gaseous products

Basketball Team Equations 15 Index cards - 5 Guards, 5 Forwards, 5 Centers Write the chemical equation for a team. Write the chemical formula for a team. How is this equation like a chemical equation? What happens to the cards left over? How does this activity demonstrate the law of conservation of mass?

Exit ticket When making soap, if 890 g of a specific fat react completely with 120 g of sodium hydroxide, the products formed are soap and 92 g glycerin. Calculate the mass of soap formed to satisfy the law of conservation of mass. Show your work and write a formula.

In your Science Notebook: Ch 21 Chemical Changes Bellwork: In your Science Notebook: 1 Write a short definition/description of each vocabulary word in your own words. 2. Draw an illustration for each work to demonstration your understanding.

Exit ticket When making soap, if 890 g of a specific fat react completely with 120 g of sodium hydroxide, the products formed are soap and 92 g glycerin. Calculate the mass of soap formed to satisfy the law of conservation of mass. Fat + sodium hydroxode - soap + glycerin 890 g + 120 g - X g + 92 g glycerin 890 g + 120 g = 1010 g – 92 g = 918 g soap

Ch 21 Chemical Changes CLE 3202.1.4 Investigate chemical and physical changes. CLE 3202.1.9 Apply the Laws of Conservation of Mass/Energy to balance chemical equations.

What are we going to learn today? I CAN: Identify reactants and products of a chemical reaction. I CAN: Determine how a chemical reaction satisfies the law of conservation of mass. I CAN: Determine how chemists express chemical changes using equations.

Exit Ticket 1. What coefficient is assumed if no coefficient is written before a formula in a chemical equation? 2. Explain why the sum of the coefficients on the reactant side of a balanced equation does not have to equal the sum of the coefficients on the product side of the equation.

Bellwork: Vocabulary Quiz Today – Study! Ch 21 Chemical Changes Bellwork: Vocabulary Quiz Today – Study!

What are we going to learn today? Identify what is meant by a balanced chemical equation. Determine how to write balanced chemical equations.

Balancing Chemical Equations 1. Write a chemical equation for the reaction using formulas and symbols. Li(s) + H2O  LiOH(aq) + H2 (g)

Balancing Chemical Equations 2. Count the atoms in reactants and products. Li(s) + H2O  LiOH(aq) + H2 (g) Li = 1 Li = 1 H = 2 H = 3 O = 1 O = 1

Balancing Chemical Equations 3. Choose coefficients that balance the equation. (Subscripts cannot be changed.) Li(s) + H2O  LiOH(aq) + H2 (g)

Balancing Chemical Equations 3. Choose coefficients that balance the equation. (Subscripts cannot be changed.) Li(s) + 2 H2O  LiOH(aq) + H2 (g)

Balancing Chemical Equations 3. Choose coefficients that balance the equation. (Subscripts cannot be changed.) Li(s) + 2 H2O  2 LiOH(aq) + H2 (g)

Balancing Chemical Equations 3. Choose coefficients that balance the equation. (Subscripts cannot be changed.) 2 Li(s) + 2 H2O  2 LiOH(aq) + H2 (g)

Balancing Chemical Equations 4. Recheck numbers of each atom on each side of the equation . 2 Li(s) + 2 H2O  2 LiOH(aq) + H2 (g) Li = 2 Li = 2 H = 4 H = 4 O = 2 O = 2

Exit Ticket 1. What coefficient is assumed if no coefficient is written before a formula in a chemical equation? 2. Explain why the sum of the coefficients on the reactant side of a balanced equation does not have to equal the sum of the coefficients on the product side of the equation.

Exit Ticket K + AlCl3  KCl + Al Balance the following equation: Which of the 5 types of chemical reactions does this represent? (Combustion, synthesis, decomposition, single displacement, double displacement)

Section 3 Classifying Chemical Reactions Bellwork: Language of Science In your Science Notebook, define the following terms: Precipitate Oxidation Reduction Catalyst Inhibitor

Ch 21 Chemical Changes CLE 3202.1.4 Investigate chemical and physical changes. CLE 3202.1.9 Apply the Laws of Conservation of Mass/Energy to balance chemical equations.

What are we going to learn today? I CAN: Identify what is meant by a balanced chemical equation. I CAN: Determine how to write balanced chemical equations. I CAN: Identify five types of chemical reactions.

Types of Chemical Reactions Combustion Reaction: Substance reacts with oxygen to produce energy in the form of heat and light 2 Mg + O2  2 MgO + light C3H8 + 5 O2  4 H2O + 3 CO2 + energy Many combustion reactions fit into other categories. (carbon+oxygencarbon dioxide is synthesis)

Types of Chemical Reactions Synthesis Reaction: Two or more substances combine to form another substance A + B  AB 2 H2 + O2  2 H2O (powers some rockets) Oxygen+Iron+Water  hydrated Iron (II) oxide (Rust)

Types of Chemical Reactions Decomposition Reaction: reverse of synthesis One substance breaks down (decomposes) into two or more substances. AB  A + B Most require heat, light or electricity. 2 H2O ---electricity---  2 H2 + O2

Types of Chemical Reactions Single Displacement Reaction: One element replaces another element in a compound A + BC  AC + B Cu + 2 AgNO3  Cu(NO3)2 + 2 Ag Copper wire in silver nitrate…Cu is more active than Ag , replaces silver, forms blue copper (II) nitrate Don’t cook iron containing vegetables like spinach in aluminum pans – Al can displace Fe in food

Types of Chemical Reactions Double Displacement Reaction: The positive ion of one compound replaces the positive ion of the other to form two new compounds. AB + CD  AD + BC Two ionic compounds in solution combine…forms precipitate, water or gas Precipitate – insoluble compound that comes out of solution

Types of Chemical Reactions Double Displacement Reaction: Ba(NO3)2 + K2SO4  BaSO4 + 2 KNO3

Oxidation – Reduction Reactions Redox Reactions – paired reactions Oxidation – loss of electrons – becomes more positive – “oxidized” Reduction – gain of electrons – becomes more negative – “reduced” Electrons pulled from one atom (oxidation) are gained by another atom (reduction) Often involve oxygen which is very reactive, pulling electrons from metallic elements - rust, corrosion

Section 4 Chemical Reactions and Energy Bellwork:

Ch 21 Chemical Changes CLE 3202.1.4 Investigate chemical and physical changes. CLE 3202.1.9 Apply the Laws of Conservation of Mass/Energy to balance chemical equations.

What are we going to learn today? I CAN: Identify the source of energy changes in chemical reactions. I CAN: Compare and contrast exergonic and endergonic reactions. I CAN: Examine the effects of catalysts and inhibitors on the speed of chemical reactions.

Identify the source of energy changes in chemical reactions. All chemical reactions release or absorb energy as chemical bonds are broken and formed. Thermal energy (heat), Light, Sound, Electricity Chemical bonds are the source of this energy. Bonds broken – requires energy Bonds formed – energy released

Compare and contrast exergonic and endergonic reactions. Exergonic – chemical reactions that release energy Less energy is required to break original bonds than is released when new bonds form Glow stick – visible light Dynamite combustion – sound energy Exothermic – thermal energy released Provide most power used in homes and industry Wood fire, heat packs, dynamite, burning fossil fuels Coal/Petroleum/Natural gas + O2  CO2(g) + energy

Compare and contrast exergonic and endergonic reactions. Endergonic – chemical reactions that absorb energy in the form of light, thermal energy, electricity Requires more energy to break bonds than is released when new ones are formed Endothermic – thermal energy absorbed Epsom salt (physical change), cold pack Barium hydroxide + ammonium hydroxide + energy… reaction absorbs so much energy that water freezes

Examine the effects of catalysts and inhibitors on the speed of chemical reactions Catalyst – substance that speeds up a chemical reaction without being permanently changed itself Catalyst can be recovered and reused Some reactions proceed too slowly to be useful Increase rate of chemical reactions Inhibitor – used to slow down a chemical reaction Food preservatives, BHT, BHA, prevent food spoilage Decrease rate of chemical reactions Do not change amount of product produced, only change rate of production

Study Guides Test (Th 1/12) – 100 pts 10 chemical equations to balance, ID type of reaction Mult Choice/Matching on Types of Reactions 1st set Language of Science Packet pages, notes, vocab Similar, not same, examples Quiz (Fri 1/13) – 15 pts Mult Choice/Matching on 2nd set of Language of Science Vocab