2/24/2010. Mr. Puccetti Spring What toxins have you encountered in your life? 2. How can toxins enter the body? 3. How can toxins harm you?

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Mr. Puccetti Spring 2010 how toxins are defined how chemists determine toxicity the mechanisms by which toxic substances act in our bodies and what this has to do with chemical reactions 1.

Consider the following chemical equation: HCl (aq) + NaHCO 3 (aq) NaCl (aq) + H 2 O(l) + CO 2 (g) 1) Predict what you might observe if this reaction was carried out.

1 Mr. Puccetti Spring 2010 how toxins are defined how chemists determine toxicity the mechanisms by which toxic substances act in our bodies and what this has to do with chemical reactions 1. What toxins have you encountered in your life? 2. How can toxins enter the body? 3. How can toxins harm you? Consider the following chemical equation: HCl (aq) + NaHCO 3 (aq) NaCl (aq) + H 2 O(l) + CO 2 (g) 1) Predict what you might observe if this reaction was carried out. Note: The chemical equation represents a change in matter using symbols and formulas. What types of information does a chemical equation give you? Consider the following chemical equation: HCl (aq) + NaHCO 3 (aq) NaCl (aq) + H 2 O(l) + CO 2 (g) Chemical equation: A chemical sentence that describes change. HCl (aq) + NaHCO 3 (aq) NaCl (aq) + H 2 O(l) + CO 2 (g) Reactants: Substances that combine with another in a chemical change. Products: Substances that are produced after a chemical reaction. Group Toxin type Effect on body Reacts with Products Molecular compounds Molecular compounds Molecular and ionic compounds Molecular and ionic compounds eyes, nose, throat, lungs Blood Acidosis Nerve Damage Kidney stones Water, H 2 O(l), in mucous O 2 (g) we breathe in HCl (aq) in stomach CaCl 2 (aq) acids and hydroxide compounds acids Metal chlorides Solid calcium compounds 1

Toxins can only enter the body in a limited number of ways. ingestion (eating or swallowing) inhalation (breathing) contact with skin Once in your body they can react in a variety of ways.

Write an interpretation (in words) of the chemical equation. b. Sodium cyanide is highly toxic. What is the most likely way it will enter the body? How do chemists keep track of changes in matter?

They also show what phase a compound is in. Toxins are substances that interact with living organisms and cause harm.

2 Toxins can only enter the body in a limited number of ways. ingestion (eating or swallowing) inhalation (breathing) contact with skin Once in your body they can react in a variety of ways. Toxins may be molecular, ionic or metallic substances. Consider this reaction between sodium cyanide and a solution of hydrochloric acid: NaCN(s) HCl(aq) NaCl(aq) HCN(g) a. Write an interpretation (in words) of the chemical equation. b. Sodium cyanide is highly toxic. What is the most likely way it will enter the body? How do chemists keep track of changes in matter? Chemical equations help chemists keep track of the substances involved in chemical changes. Chemical equations use chemical formulas to indicate the reactants and products of chemical changes. They also show what phase a compound is in. Toxins are substances that interact with living organisms and cause harm. Consider the following chemical equation: AgNO 3 (aq) + KCl (aq) KNO 3 (aq) + AgCl (s) 1. What do you expect to observe if you carry out the procedure? 2. Translate the above chemical equation into writing, describing what is taking place. Work in groups of four. Wear safety goggles at all times. Do not touch the dry ice with your fingers. It causes burns. NaOH, Ca(OH) 2, and NH 4 OH can irritate or burn skin. In case of a spill or contact with skin, rinse with large amounts of water. CaCl 2 (s) + 2 NaOH (aq) Ca(OH) 2 (s) + 2 NaCl (aq) Chemical equations allow you to predict and track changes in matter on an atomic level. You can translate the chemical symbols into chemical names. Chemical Names: calcium chloride sodium hydroxide calcium hydroxide sodium chloride Phase Symbols: (g) (l) (s) (aq) 2

The (aq) tells you if a dissolved ionic substance is present and that water is present. The (s) on the product side means that you can see the ionic solid.

How can you predict what you will observe based on a chemical equation? Chemical equations allow chemists to predict and track changes in matter.

3 The (aq) tells you if a dissolved ionic substance is present and that water is present. The (s) on the product side means that you can see the ionic solid. A solid that forms in the solution of water is called a precipitate. There is some information that a chemical equation can t provide. Ex s? How can you predict what you will observe based on a chemical equation? Chemical equations allow chemists to predict and track changes in matter. They indicate how many products are formed, what those products are, and the phase of each product. CaCl 2 (s) + 2 NaOH (aq) Ca(OH) 2 (s) + 2 NaCl (aq) Examine this chemical equation. Write an interpretation of the chemical equation, describing what is taking place. Is there a precipitate in the products? Explain. CaCl 2 (aq) + 2NaOH(aq) Ca(OH) 2 (s) 2NaCl(aq) The following two equations both describe what happens when dry ice is placed in water: CO 2 (s) CO 2 (g) CO 2 (s) + H 2 O (l) H 2 CO 3 (aq) 1. What differences do you see in these two equations? 2. Why do you think two equations are needed to describe what happens? Physical changes are changes in the appearance or form of a substance. CO 2 (s) CO 2 (g) Chemical changes produce new substances with new properties. CO 2 (s) + H 2 O (l) H 2 CO 3 (aq) CO 2 (s) CO 2 (g) H 2 O (s) H 2 O (l) Physical changes are changes in the appearance or form of a substance. Physical changes do not produce new substances. The formulas are the same on both sides of the equation but the phase changes. 3

4 CO 2 (s) + H 2 O (l) H 2 CO 3 (aq) Chemical changes produce new substances with new properties. Chemical changes result from chemical reactions. The chemical formulas on either side of the equation change. The products are different than the reactions. Is dissolving a physical or chemical change? Sugar dissolving: C 6 H 12 O 6 (s) C 6 H 12 O 6 (aq) Calcium chloride salt dissolving: CaCl 2 (s) CaCl 2 (aq) CaCl 2 (s) Ca 2+ (aq) + 2 Cl - (aq) Is dissolving a physical or chemical change? Sugar dissolving: C 6 H 12 O 6 (s) C 6 H 12 O 6 (aq) Calcium chloride salt dissolving: CaCl 2 (s) CaCl 2 (aq) CaCl 2 (s) Ca 2+ (aq) + 2 Cl - (aq) Does the following chemical equation describe a physical change or a chemical change? Explain how you can tell. C 17 H 17 O 3 N(s) + 2C 4 H 6 O 3 (l) C 21 H 21 O 5 N(s) + 2 C 2 H 4 O 2 (l) Dissolving is most often classified as a physical change. It is clearly a special case that could be considered in a gray area between physical and chemical change. It is possible to argue that dissolving a substance in water changes the properties of that substance. How does mass change during a chemical or physical change? Reaction A: Na 2 CO 3 (aq) + CaCl 2 (aq) NaCl (aq) + CaCO 3 (s) 1. Describe what you will observe when Na 2 CO 3 (aq) and CaCl 2 (aq) are mixed. 2. Will the mass increase, decrease, or stay the same after mixing? Explain your reasoning. >? g Reactants > <? g Products? g? g Reactants < Products 4

Lab Materials: Law of Conservation of Mass: Matter can be neither created nor destroyed in physical and chemical changes.

On the planet there is essentially an unchanging number of atoms. How does mass change during a physical or chemical change?

g < 2 NaCl (aq) + H 2 O (l) + CO 2 (g) How does mass change during a physical or chemical change?

Na 2 CO 3 (aq) + 2 HCl (aq) Mass is conserved.? g? g 2 NaCl (aq) + H 2 O (l) + CO 2 (g) How does mass change during a physical or chemical change?

5 Lab Materials: Law of Conservation of Mass: Matter can be neither created nor destroyed in physical and chemical changes. NaCl CaCl 2 C 2 H 4 O 2 Na2 CO 3 This means that atoms do not come in and out of existence. They are simply rearranged. Since atoms have mass, the mass does not change. On the planet there is essentially an unchanging number of atoms. How does mass change during a physical or chemical change? Mass is conserved in chemical reactions: the total mass of the products equals the total mass of the reactants. Gases have mass. Na 2 CO 3 (aq) + 2 HCl (aq) >? g? g < 2 NaCl (aq) + H 2 O (l) + CO 2 (g) How does mass change during a physical or chemical change? Individual atoms are conserved in chemical reactions and physical changes: the number of atoms of each element remains constant from start to finish. Atoms are conserved. Na 2 CO 3 (aq) + 2 HCl (aq) Mass is conserved.? g? g 2 NaCl (aq) + H 2 O (l) + CO 2 (g) How does mass change during a physical or chemical change? The Law of Conservation of Mass states that matter can be neither created nor destroyed in physical and chemical changes. Atoms are conserved. Na 2 CO 3 (aq) + 2 HCl (aq) Mass is conserved. 2 NaCl (aq) + H 2 O (l) + CO 2 (g) Consider this reaction: CuCO3(s) + H2SO4(aq) CO2(g) + CuSO4(aq) + H2O(l) a. Describe what you will observe when copper (II) carbonate, CuCO 3 (s), and sulfuric acid, H 2 SO 4 (aq), are mixed. b. Will the mass increase, decrease, or stay the same after mixing? Explain.? g? g 5

How do you balance atoms in chemical equations? Write the following equation: CuCl 2 (aq) + Na 2 S (aq) CuS (s) + NaCl (aq) Does this equation obey the law of conservation of mass? Why or why not?

6 How do you balance atoms in chemical equations? Write the following equation: CuCl 2 (aq) + Na 2 S (aq) CuS (s) + NaCl (aq) Does this equation obey the law of conservation of mass? Why or why not? C 3 H 8 (g) + 5 O 2 (g) 3 CO 2 (g) + 4 H 2 O (l) The numbers in blue are subscripts. They do not change. The numbers in red are coefficients. They can change to balance the equation. C 3 H 8 (g) + 5 O 2 (g) 3 CO 2 (g) + 4 H 2 O (l) CH 4 (g) + O 2 (g) CO 2 (g) + H 2 O(g) The molecular formulas indicate the number of atoms that combine to form a molecule. The coefficients show the number of molecules involved in a chemical equation. Inventory of Atoms Reactants Products 1 C 1 C 4 H 2 H 2 O 3 O CH 4 (g) + O 2 (g) CO 2 (g) + 2H 2 O(g) Inventory of Atoms Reactants Products 1 C 1 C 4 H 4 H 2 O 4 O CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(g) Inventory of Atoms Reactants Products 1 C 1 C 4 H 4 H 4 O 4 O 6

How do you balance atoms in chemical equations? CuCl 2 (aq) + Na 2 S (aq) CuS (s) + 2 NaCl (aq) In order to conserve matter, the number of atoms on both sides of a chemical equation must be equal.

Balance the following equation: Ca + O 2 CaO Consider the following reactions: Tl 2 O (s) + 2 HCl (l) 2 TlCl (aq) + H 2 O (l) 2 CH 2 O (aq) + O 2 (g) 2 CH 2 O 2 (aq) How are these two reactions

Thallium Poisoning (Tl) Formaldehyde Poisoning (CH 2 O) H 2 O 2 N 2 F 2 I 2 Cl 2 Br 2 HONFIClBr Diatomic molecules are 2 atom molecules. They are found paired to complete their octet of electrons.

7 How do you balance atoms in chemical equations? CuCl 2 (aq) + Na 2 S (aq) CuS (s) + 2 NaCl (aq) In order to conserve matter, the number of atoms on both sides of a chemical equation must be equal. When an equation is balanced it tells you how many molecules or moles of each substance take part in a reaction and how many molecules or moles of product(s) are produced. Balance the following equation: Ca + O 2 CaO Consider the following reactions: Tl 2 O (s) + 2 HCl (l) 2 TlCl (aq) + H 2 O (l) 2 CH 2 O (aq) + O 2 (g) 2 CH 2 O 2 (aq) How are these two reactions different from each other? How would you describe, in words, what happens to the reactants in each case? Thallium Poisoning (Tl) Formaldehyde Poisoning (CH 2 O) H 2 O 2 N 2 F 2 I 2 Cl 2 Br 2 HONFIClBr Diatomic molecules are 2 atom molecules. They are found paired to complete their octet of electrons. They need to be written as a pair in chemical equations before you balance. H O N F Cl Br I How do atoms rearrange to form new products? Chemical reactions can be sorted into categories depending on how the atoms in the reactants rearrange to form the products. The four most general types of chemical change are combination reactions, decomposition reactions, single exchange reactions, and double exchange reactions. CO 2 (g) + NaOH (aq) NaHCO 3 (aq) Combination Reaction: Several reactants combine to form a single product. There is only one compound on the product side of the equation. 7

8 Decomposition Reaction: The compound you are starting with is broken into pieces as a result of a chemical change. There is only one reactant. CaCO 3 (aq) CaO (aq) + CO 2 (g) Cl 2 (g) + CaI 2 (s) CaCl 2 (s) + I 2 (s) Single exchange: A compound breaks apart and one piece combines with the other reactant. Typically one of the reactants is an element. AgNO 3 (aq) + KCl (aq) AgCl (s) + KNO 3 (aq) Double exchange: Both reactants break apart then the parts recombine into two new products. The two reactants exchange ions. Combination Decomposition Single exchange CO 2 (g) + NaOH(aq) NaHCO 3 (aq) CaCO 3 (aq) CaO(aq) + CO 2 (g) Cl 2 (g) + 2NaBr(s) 2NaCl(s) + Br 2 (l) Double exchange 2AgCl(s) + BaBr 2 (aq) 2AgBr(s) + BaCl 2 (aq) Combination Decomposition Single exchange A + B AB AB A + B A + BC AC + B Examine the following chemical equation describing a double exchange reaction. Predict the products. Make sure the equation is balanced. CaCl 2 (aq) + NaCO 3 (aq) Ca (s) + (aq) Double exchange AB + CD AD + CB 8

Classifying Chemical Reactions

1 Classifying Chemical Reactions Analyzing and Predicting Products Introduction The power of chemical reactions to transform our lives is visible all around us-in our cars, even in our bodies. Chemists