CHEMISTRY NOTES Chapter 6

No need to copy! Section 1 Atoms, Elements, Compounds Atoms Elements Compounds Chemical Bonds van der Waals Forces Section 2 Chemical Reactions Reactants and Products Energy of Reactions Enzymes

Section 3 Water and Solutions Water Polarity Mixtures with Water Section 4 The Building Blocks of Life Organic Chemistry Macromolecules

Section 1 Chemistry: the study of matter, it’s composition and properties. Atoms: The building blocks of matter. Matter: Anything that has mass and takes up space Elements: Made of only 1 type of atom. (oxygen, hydrogen, gold)

ATOMS Smallest particle of element having the element’s properties Nucleus contains protons and neutrons. Electron cloud surrounds nucleus and contains electrons. # of protons = # of electrons

Know this! Carbon has 6 protons, 6 neutrons and 6 electrons!

Number of protons = number of electrons and the number of neutrons.

Electron Cloud Energy levels: 2 electrons in first level, 8 in second, 18 in third. Valence electrons: electrons in outer energy level Valence electrons create bonds with other atoms.

You must imagine it in 3 dimensions!

Carbon has 2 electrons in the first shell and 4 in the second. It can form 4 bonds because it can have 8 electrons in the 2nd shell.

Elements Everything is made of elements. Elements are substances that cannot be broken down into simpler chemical substances. Only 25 elements are needed by humans. C, H, O, & N make up 96% of your mass! (Carbon, hydrogen, oxygen and nitrogen.)

Know what the atomic number and atomic mass represent! (8th grade benchmark.)

Compounds Atoms bond together to become more stable and form compounds. NaCl sodium chloride (salt) H2O water HCl hydrochloric acid C6H12O6 glucose

Compounds always form from a specific combination of elements in a fixed ratio. Ex: water is always 2 H’s and 1 O = H2O Glucose = 6 C’s 12 H’s 6 O’s = C6H12O6 Compounds form when 2 or more elements combine by bonding together.

Bonds between Atoms Forming bonds stores energy.

2 types of Chemical Bonds Covalent bond = when atoms share electrons Ex: H2O (water)

Examples of covalent bonds.

Can you have more than one covalent bond? Yes!

When an electron is transferred to another atom. This creates a bond! Ionic Bonding: When an electron is transferred to another atom. This creates a bond! Remember the first shell needs 2, the 2nd shell needs 8!

Example of ionic bonding Ions are created in ionic bonding. One atom will be positive and one atom will be negative. Pg 153

Magnesium chloride

van der Waals Forces Elements in a covalent bond do not always share electrons equally. Some molecules will have areas that are more positive and areas that are more negative. This causes molecules to be attracted to each other.

The bonds between water molecules are an example! These are called hydrogen bonds.

Van der Waals forces allow the toes of a gecko to stick to surfaces.

Section 2 Chemical Reactions The process by which atoms or groups of atoms of substances are reorganized into different substances. EX: photosynthesis

Chemical Equations Substances that undergo chemical reactions are called reactants. Substances formed by chemical reactions are called products REACTANTS  PRODUCTS

2H2 + O2  2H2O What do the numbers mean? The number before each chemical formula represents the number of molecules. Called the coefficient. The subscripts indicate the number of atoms of each element. A chemical equation is balanced when the numbers of atoms of each element are equal on each side of the arrow.

2H2 + O2  2H2O Practice: How many atoms of H? 2 x 2 = 4 Coefficient = number of molecules Subscript = number of atoms Multiply the coefficient time the subscript! 2H2 + O2  2H2O How many atoms of H? 2 x 2 = 4 How many atoms of O? 1 x 2 = 2

Law of Conservation of Mass Why must chemical equations be balanced? Law of Conservation of Mass In a chemical reaction, matter is neither created nor destroyed. You can change matter but you can’t create or destroy matter! 2H2 + O2  2H2O

How do you check to see if an equation is balanced? Count the atoms! N2O + NO2 3NO balanced N = 3 N = 3 O = 3 O = 3

How do you balance an equation? K + H2O H2 + KOH unbalanced K = 1 K = 1 H = 2 H = 3 0 = 1 O = 1 Change the coefficient, not the subscript! 2K + 2H20 H2 + 2KOH balanced! K = 2 K = 2 H = 4 H = 4 0 = 2 O = 2

Energy of Reactions You need energy to start a chemical reaction! This is called activation energy. Ex: Candles don’t burn on their own…they need a spark

Exothermic = releases energy 2 types of reactions: Exothermic = releases energy Endothermic = absorbs energy Pg 158

Exothermic Reaction Lighting a candle: the flame from the match is the activation energy Candle releases energy in the form of heat and light!

Endothermic Reaction Absorb more energy than they release!

Is this endothermic or exothermic? You will need to be able to tell the difference on the test!!!!

Enzymes Enzymes lower the amount of activation energy for the biochemical reactions in cells. Enzymes are catalysts—they increase the rate of reactions. Words that end in –ASE are enzymes.

This is what happens when you add an enzyme to a reaction! The green line represents the amount of energy needed when there is an enzyme!

Examples of enzymes: Amylase – breaks down amylose, one of the components of starch This speeds up digestion!

Note! Different enzymes require different pH levels!

Example 2: Lactase helps break down lactose which is a type of sugar found in milk! If you are lactose intolerant, it means you don’t have lactase in your small intestines.

Enzyme (glucoamylase) breaking down starch.

How do enzymes work? Enzymes are special proteins that speed up biological processes. They are specific to the reaction they are affecting. They have an active site that matches the substrate. The active site and substrate connect and then help break bonds in the reactants.

Know these: Enzyme Active Site Substrate

pH and temperature changes can affect the shape of an enzyme pH and temperature changes can affect the shape of an enzyme. The enzyme may become inactive!

Section 3 Water Polarity Mixtures with water

Water 70% of your cells mass is water Water is polar Polarity: areas of unequal charge Water molecules attract each other and other polar molecules

Hydrogen bonding occurs between water molecules. Remember van der Waals forces!

the molecules are attracted to each other Water is cohesive. Cohesive: the molecules are attracted to each other because of the hydrogen bonds. Cohesion is the reason water makes a ball shape.

This creates surface tension!

Water is adhesive. Adhesion: Water is attracted to polar surfaces.

Capillary action is the result of adhesion.

Water has a high specific heat. It absorbs alot of heat before it gets hot. The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius. This makes water important in keeping the temperature of your body stable. Also true for oceans, lakes and rivers.

Why is the specific heat so high? Because of the hydrogen bonds between water molecules. The molecules don’t move much as they are heated!

Water is a universal solvent. a substance in which another substance (solute) is dissolved. It will dissolve compounds that are polar, like salt!

pH Measure of how acidic or basic a substance is. Acid: any substance that forms H+ ions in water (stomach acid) Base: any substance that forms OH- ions in water (Draino)

Homework: pg 164 Data Analysis Lab pH and Biological Processes Most biological processes occur between pH 6.5 and 7.5. Buffers: Mixtures that react with acids and bases to control the pH. This helps maintain homeostasis! Your blood has buffers that keep the pH about 7.4 Homework: pg 164 Data Analysis Lab

Section 4 The Building Blocks of Life Organic Chemistry Macromolecules

Organic Chemistry Life on earth is carbon-based. Carbon has 4 electrons in its outer shell and can form 4 covalent bonds.

Macromolecules Large molecules that are formed by joining smaller molecules. Also called polymers which are repeating units of compounds called monomers.

Macromolecules 4 major categories of biological molecules: Carbohydrates Lipids Proteins Nucleic acids

1.Carbohydrates Store short term energy (glycogen) Think carb loading for a marathon! Provide support (cellulose in cell walls) Composed of carbon, hydrogen and oxygen - 1:2:1 ratio Monosaccharides = one sugar, like glucose, C6H12O6 Disaccharides = 2 chained monosaccharides

C6H12O6 monosaccharide disaccharide C12H22O11

2. Lipids Mostly carbon and hydrogen, less oxygen. Fats, oils, waxes. Hydrophobic – don’t dissolve in water. Provide more energy than carbohydrates! Energy is used during migration or hibernation! Basic structure includes fatty acid tails.

This will be important when we study the cell membrane!

3. Proteins C, H, O, Nitrogen, and sometimes Sulfur Amino acids: building blocks of proteins Proteins provide structure for body parts Enzymes: proteins that speed up the rate of chemical reactions!

Enzymes are a protein made of amino acids.

Proteins in your body!

4. Nucleic acids Stores information in cells in the form of a code Nucleotides: subunits of nucleic acids 2 types of nucleotides DNA: hereditary information RNA: important in making proteins

Nucleotide : the smallest unit of nucleic acids. (remember this shape!)

The nucleotides connect together to make DNA or RNA.