Chemical Changes

Physical Change When matter changes size, shape, or phase Particles are not taken out or added into the substance The position of the particles can change Making a bat out of wood

Physical properties Properties that you can observe just by looking and touching Can you think of any examples? Color Texture Toughness

What is a chemical change A change in a substance that you can’t get it back to the original state once it has been changed Driving in a car and using gasoline for fuel is a chemical change Rust

Chemical Properties: Properties that can be observed only when substances interact with each other Chemicals mix and they pop or release heat What happens when you heat up a can that has flammable gas in it?

Chemical Reaction The reaction between two different atoms that creates chemical bonds A chemical bond is formed from sharing electrons

Reactants and products The substance that disappears after the chemical change Products The substance that appears after the chemical change

Reactants and products picture

Reactions requires energy This energy is called activation energy For a reaction to take place a reaction must get a certain amount of energy to take place If the energy doesn’t reach this point the reaction does not take place

Reactions sometimes need help Help comes from catalysts These are chemicals that lowers the energy rate so a reaction can occur It allows the reaction to proceed more quickly or at a lower temperature You can look at it like building a railroad tunnel instead of going over a mountain

Two types of chemical bonds Covalent bond A bond where the electrons are equally shared Ionic bond A bond where one atom gains the electrons that are being traded in the chemical bond This changes the atom’s charge

Ionic Bonding

Ionic Bond causes two products Cation The atom that loses the electron The charge of that atom becomes positive “Plussy Cat” Anion The atom that gains the electron The charge of that atom becomes negative “Negative Annie”

Types of chemical reactions Decomposition Reaction Spontaneous Reaction Substitution Reaction Synthesis Reaction Endothermic Reaction Exothermic Reaction

Decomposition Reaction This is a reaction that breaks down the compounds into it’s simple form For example H20  H2 + O In this cartoon the egg (the reactant), which contained the turtle at one time, now has opened and the turtle (product) and egg shell (product) are now two separate substances

A synthesis reaction Two or more simple substances combine to form a more complex substance In other words, two or more reactants yielding one product For example The skinny bird (reactant) and the worm (reactant) combine to make one product, a fat bird.

Spontaneous Reaction A reaction that occurs without being driven by some outside force. They may occur quickly or slowly For example Carbon turning into diamonds Combustion of hydrogen

Substitution reaction When one atom is switched or replaced by another atom in a reaction For example CH3Cl + -OH  CH3OH + Cl-

A chemical reaction requires the transfer of energy There are two types of reactions when looking at the transfer of energy Exothermic Endothermic

A reaction can be either exothermic or endothermic Exothermic reaction Gives off energy in forms of heat or light Endothermic reaction Needs energy for the reaction to take place or requires heat This reaction feels cold

Activity Series This is a list based on how reactive a metal might be Lithium Li --> Li+ + e- Potassium K --> K+ + e- Barium Ba --> Ba2+ + 2 e- Calcium Ca --> Ca2+ + 2 e- Sodium Na --> Na+ + e- Magnesium Mg --> Mg2+ + 2 e- Aluminum Al --> Al3+ + 3 e- Manganese Mn --> Mn2+ + 2 e- Zinc Zn --> Zn2+ + 2 e- Chromium Cr --> Cr3+ + 3 e- Iron Fe --> Fe2+ + 2 e- Cobalt Co --> Co2+ + 2 e- Nickel Ni --> Ni2+ + 2 e- Tin Sn --> Sn2+ + 2 e- Lead Pb --> Pb2+ + 2 e- Hydrogen H2 --> 2 H+ + 2 e- Copper Cu --> Cu2+ + 2 e- Silver Ag --> Ag+ + e- Mercury Hg --> Hg2+ + 2 e- Platinum Pt --> Pt2+ + 2 e- Gold Au --> Au3+ + 3 e Activity Series This is a list based on how reactive a metal might be On this list the most reactive metals are on the top needing only one electron

A metal that is not likely to react is called a stable metal These metals are usually found in the middle of the periodic table The non-stable metals are found on the edges of the periodic table Like Alkali Metals Activity Series will help determine if a metal is more likely to react than another