Catalyst What kind of bonds would these chemicals in the human body make? How can we tell? What are the other two kinds and what types of elements do they involve?

Unit 2 Exam Review

BBC Clip

Death Penalty Reading

Unit 3 Theme – Why does the same chemical both help and Hurt me?

Balancing Equations Exploration With your partner, complete the simulator on the computer Complete the entire handout. Be sure to defend your reasoning!

Lecture 3.1 – Balancing Chemical equations

Today’s Learning Targets LT 3.1 – I can discuss the law of conservation of mass and how it relates to chemical reactions. LT 3.2 – I can explain how to balance a chemical reaction.

What is the law of conservation of mass?

I. Law of Conservation of Mass The law of conservation of mass states that matter cannot be created or destroyed, it can only change forms. Therefore, we cannot destroy something. All we can do is change the form.

How are states indicated in chemical reactions?

TNT!

TNT Explosion C 7 H 5 N 3 O 6 → N 2 + H 2 O + CO + C

I. Chemical Reactions Substances react to form new substances Chemical equations are used to explain a reaction that occurs.

TNT Reaction C 7 H 5 N 3 O 6 → N 2 + H 2 O + CO + C ElementBefore Reaction? After Reaction? C ✔✔ H ✔✔ N ✔✔ O ✔✔

I. Chemical Reactions Reactants  Products ReactantsProducts C 7 H 5 N 3 O 6 → N 2 + H 2 O + CO + C

II. States of Molecules A molecule can be in a solid, liquid, gas, or aqueous state Aqueous means dissolved in water We abbreviate these as: – (s) = solid – (l) = liquid – (g) = gas – (aq) = aqueous

Table Talk With your table, label the products, the reactants, and the state of each compound. NH 4 OH (aq) + FeCl 3 (s)  NH 4 Cl (s) + Fe(OH) 3 (aq)

Stop and Jot For the following reaction, label the products, the reactants, and the state of each compound: H 2 O 2 (aq) + NaBr (s)  NaOH (aq) + H 2 O (l) + O 2 (g)

How do you balance chemical reactions?

I. Balancing Chemical Reactions Need same amount of products and reactants to satisfy law of conservation of mass We balance chemical equations to achieve this

II. Tips for Balancing Chemical Reactions We CANNOT change the subscripts. We can change the number in front of the substance, known as the coefficient. 2 NaCl Coefficient This means we have 2 Na and 2 Cl

III. Organizing Our Thoughts

Uh oh…something is wrong here

Why is this one better?

Class Example Balance the following chemical reaction: ____H 2 O 2  ___ H 2 O + ____O 2

Class Example Balance the following equation: __AgNO 3 + ___Na 2 CrO 4  __ Ag 2 CrO 4 +___ NaNO 3

Table Talk Balance the following equation: Mg + FeCl 3  MgCl 2 + Fe

Extra Examples ___ C 3 H 6 + ____ H 2 O  ___ C 3 H 8 + __ O 2 ___ Mg + ___ FeCl 3  ___ MgCl 2 + ___ Fe __ H 2 O + __ Fe 2 (SO 4 ) 3  __ Fe 2 O 3 + __ H 2 SO 4 + ___ H 2 O + ___ H 2

Balancing Chemical Reactions with Candy Each candy piece represents one element or atom. The problem will tell you what each candy represents.

Exit Ticket 1. What does the law of conservation of mass state? 2. Label the products and reactants in the following reaction NaOH + HCl  NaCl + H 2 O 3. Balance the following equation. __ NH 4 OH + __ FeCl 3  __ NH 4 Cl +___ Fe(OH) 3

Closing Time Homework 3.1 Quiz on Balancing Equations