Chemical Reactions Page 21 in Unit 1 & 2 Folder

Compounds Compound- substance that contains 2 or more elements chemically combined (can only be separated by chemical means). Ex: H2O or NaCl Molecule- Smallest part of a compound that still displays the properties of that compound. Ex: There are millions of molecules of H2O that make up one drop of water.

Chemical Bonding Chemical Bonding- how 2 or more atoms join or are held together to form a compound (electrons are the “glue” that holds atoms together). Ionic Bond- the transfer of electrons from one atom to another. The result will leave on atom electrically negative (anion) & the other electrically positive (cation) (Ion=charged particle) Sodium atom (Na) Chlorine atom (CI) Sodium ion (Na+) Chloride ion (CI-) Na loses an electron to CI ionic bond gained electron

Chemical Bonding Continued Covalent Bond- the sharing of electrons between 2 atoms (no change in charge occurs) covalent bonds Oxygen atom (O) Carbon atom (C) Carbon dioxide (CO2 ) Chemical Bonds

The red numbers tell us how many individual atoms there are combining. Chemical Reactions Let’s look at that chemical bond a little closer. We had 2 oxygen atoms come together to share electrons with 1 carbon atom. These three atoms are called the reactants because they react together to form something. Together they produced CO2. CO2 is the product – it was produced during the chemical reaction. Oxygen atom (O) Carbon atom (C) Carbon dioxide (CO2 ) 2O + 1C  CO2 The red numbers tell us how many individual atoms there are combining. The brown number tells us how many oxygen atoms there are in the compound.

The red now shows the reactants. The brown now shows the products. Chemical Reactions Reactants – the substances that are changed during a chemical reaction Products – the substances made by a chemical reaction (the arrow always points to the products) 2O + 1C  CO2 The red now shows the reactants. The brown now shows the products. Oxygen atom (O) Carbon atom (C) Carbon dioxide (CO2 )

Now You Try: Chemical Reactions Copy this into your notes: To make a water molecule, you must take 2 hydrogens (H) and combine them with 1 oxygen. What would this chemical reaction look like? Label the reactants. Label the products. Label what each of the numbers mean.

Chemical Reactions Some chemical reactions use energy. These are called endothermic reactions. Bond energy – the amount of energy that it takes to break a bond Activation energy – the amount of energy that it takes to begin a chemical reaction Some chemical reactions also release energy. These are called exothermic reactions.

Enzymes Speed up Reactions Activation energy for a chemical reaction is like the energy someone needs to push a large rock up a hill. Under normal conditions, the hill is steep and requires a lot of energy to push the rock up. Catalysts are substances that decrease the activation energy (size of the hill) needed to start a reaction.

Enzymes Speed up Reactions Enzymes are special catalysts that help speed up processes in living things.

How do Enzymes Work? Enzymes are a special shape that allows them to fit two or more reactants together. The reactants that fit in the enzyme are called substrates. Then, the enzyme holds onto the reactants and lowers the amount of energy needed for them to change into the products. The completed products exit the enzyme and continue on into the body.

Enzyme Jobs Each type of enzyme is responsible for a different chemical reaction. This is because the shape of the enzyme is specifically designed to only fit certain reactants.

Enzyme Names Enzymes almost always end in “-ase” Catalase, invertase, and anhydrase are examples. Some exceptions are pepsin and trypsin which both help with digestion in the body.

Enzyme Shape The Enzyme’s shape is very important. If it is not the right shape, the substrates won’t fit. Changes in pH and Temperature can change the enzyme’s shape, making it not work anymore.

Think About It How could getting a fever affect an enzyme? How could drinking too much soda (which has a lot of acid) affect an enzyme?