Unit 4: Toxins Intro Chemistry

Chemical Toxins Chemistry is the study of matter and the changes that it undergoes. Chemistry is the study of matter and the changes that it undergoes. We have learned about how chemical compounds are formed We have learned about how chemical compounds are formed We have also learned the language of chemistry, chemical formulas We have also learned the language of chemistry, chemical formulas Certain chemicals interact with the human body in a negative way and are known as toxins Certain chemicals interact with the human body in a negative way and are known as toxins Now we will equations for chemical reactions to learn about toxic substances. Now we will equations for chemical reactions to learn about toxic substances.

Keeping Track of Atoms

Law of Conservation of Matter Conservation of Matter: in all chemical and physical changes, matter is neither created or destroyed Conservation of Matter: in all chemical and physical changes, matter is neither created or destroyed The total mass in a chemical reaction remains constantThe total mass in a chemical reaction remains constant Antoine Lavoisier: Antoine Lavoisier: Made accurate and precise measurements during chemical reactionsMade accurate and precise measurements during chemical reactions Found that the total mass at the beginning = total mass at end of reactionFound that the total mass at the beginning = total mass at end of reaction

Chemical Reactions A chemical change is really a chemical reaction A chemical change is really a chemical reaction Has two parts: Has two parts: Reactants: the substances you start withReactants: the substances you start with Products: the substances you end up withProducts: the substances you end up with The reactants turn into the products The reactants turn into the products 4 Fe + 3 O 2  2 Fe 2 O 3 Reactants  products

Ways to Express a Chemical Reaction The way atoms are joined is changed in a chemical reaction. The way atoms are joined is changed in a chemical reaction. Can be described several ways: Can be described several ways: 1. In a sentence Copper reacts with chlorine to form copper (II) chloride. 2. In a word equation Copper + chlorine  copper (II) chloride 3. In chemical formulas: Cu + Cl 2  CuCl 2

Symbols in equations- the arrow  separates the reactants from the products the arrow  separates the reactants from the products (s) or  after the formula = solid (s) or  after the formula = solid (g) or  after the formula = gas (g) or  after the formula = gas (l) after the formula = liquid (l) after the formula = liquid (aq) after the formula - dissolved in water, an aqueous solution (aq) after the formula - dissolved in water, an aqueous solution

Symbols used in equations indicates a reversible reaction indicates a reversible reaction shows that heat is supplied to the reaction shows that heat is supplied to the reaction is used to indicate a catalyst is supplied, in this case, platinum. is used to indicate a catalyst is supplied, in this case, platinum.

What is a catalyst? A catalyst is a substance that speeds up a reaction, without being changed or used up by the reaction. A catalyst is a substance that speeds up a reaction, without being changed or used up by the reaction. Enzymes are biological or protein catalysts. Enzymes are biological or protein catalysts.

Skeleton and Balanced Equations Use formulas and symbols to describe a reaction Use formulas and symbols to describe a reaction Don’t indicate how many of each element/compound Don’t indicate how many of each element/compound Balanced equations: the number of atoms of each element is the same on both sides of the reaction. Balanced equations: the number of atoms of each element is the same on both sides of the reaction. Use coefficients to balance equation Use coefficients to balance equation

Coefficients and Subscripts Coefficients: large whole numbers placed in front of formula which represents number of units of that compound Coefficients: large whole numbers placed in front of formula which represents number of units of that compound Subscript: small whole number placed in chemical formula to represent number of atoms of an element in a compound Subscript: small whole number placed in chemical formula to represent number of atoms of an element in a compound

4 Fe + 3 O 2  2 Fe 2 O 3 Coefficient subscript

Study Buddy Review What is the Law of Conservation of mass? What is the Law of Conservation of mass? What does the symbol (l) mean? What does the symbol (l) mean? What does (aq) mean? What does (aq) mean? What is a coefficient? What is a coefficient? What is a subscript? What is a subscript?

How to Balance Chemical Equations

Balanced Equation A balanced equation has the same number of atoms of each element on both sides of the equation A balanced equation has the same number of atoms of each element on both sides of the equation Atoms can’t be created or destroyed Atoms can’t be created or destroyed All the atoms at the beginning must appear in the end All the atoms at the beginning must appear in the end

C + O 2  CO C + O 2  CO We need one more oxygen in the products. We need one more oxygen in the products. Can’t change the formula, because it describes what it is (carbon monoxide in this example) Can’t change the formula, because it describes what it is (carbon monoxide in this example) C + O  C O O

Must be used to make another CO Must be used to make another CO But where did the other C come from? But where did the other C come from? C + O  C O O O C

Must have started with two C Must have started with two C 2 C + O 2  2 CO 2 C + O 2  2 CO C + O  C O O O C C

Rules for balancing:  Assemble, write the correct formulas for all the reactants and products  Count the number of atoms of each type of element appearing on both sides  Balance the atoms of an element one at a time by adding coefficients (the numbers in front) - save H and O until LAST!  Check to make sure it is balanced.

Never change a subscript to balance an equation. Never change a subscript to balance an equation. If you change the formula you are describing a different reaction.If you change the formula you are describing a different reaction. H 2 O is a different compound than H 2 O 2H 2 O is a different compound than H 2 O 2 Never put a coefficient in the middle of a formula Never put a coefficient in the middle of a formula 2 NaCl is okay, Na2Cl is not.2 NaCl is okay, Na2Cl is not.

Balancing Equations Examples H 2 (g)+ O 2 (g)  H 2 O (l) H 2 (g)+ O 2 (g)  H 2 O (l) Zn + HCl  H 2 + ZnCl 2 Zn + HCl  H 2 + ZnCl 2 Pb (NO 3 ) 2 + K 2 S  PbS + KNO 3 Pb (NO 3 ) 2 + K 2 S  PbS + KNO 3