Notes—Physical and Chemical Properties and Changes Physical and Chemical Properties are used to identify a substance and help us figure out how materials are suited for different uses (based on their physical and chemical properties). Some physical properties and ALL chemical properties are considered to be characteristic properties; this means that no matter how much of the substance is present, those properties always stay the same.

Label blocks as shown below: Directions: Divide notebook page into 4 blocks Label blocks as shown below: Physical Properties Chemical Properties Physical Changes Chemical Changes

PHYSICAL PROPERTIES ARE: characteristics that can observed without changing it; observations are made using one’s senses and with measurement tools. For example: shape Length Mass Volume Weight Density Boiling point Melting/freezing point Hardness State of matter Luster Color Texture Solubility (ability to dissolve) Taste Odor Malleability Ductility

CHEMICAL PROPERTIES: are properties that describes matter’s ability to react to to form new & different substances this means that the original substances is chemically altered. For example, the ability to rust is a chemical property. The iron has reacted with oxygen and the original iron metal is changed. It now exists as iron oxide (rust), a different substance.

Sample chemical properties: Flammability Ability to rust (oxidize) Ability to bleach Combustibility (burning of fuel and oxidant) Ability to react with an acid or base Ability to react with water, forming a gas

A Physical Change: is a change in the physical properties of matter does not chemically change or alter the substance -One type of physical change: Is a phase change. The matter changes its phase or state (solid, liquid and gas.) what the substance is made of (composition) does not change during a phase change; only its physical appearance changes Examples: Melting, freezing, condensation, vaporization

Phase changes are physical changes

Chemical Changes: Chemical changes occur when: occur when one or more substances are changed to a new substance Chemical changes occur when: 2 or more reactants  new products For example: combustion of Isopropyl alcohol 2C3H7OH + 9 O2  6 CO2 + 8 H2O (alcohol + oxygen)  carbon dioxide + water)

Clues or signs that show that a chemical change may have occurred are: Gas bubbles are produced A change in color A change in temperature (not due to an external heat or cooling source) A precipitate forms (when 2 liquids are combined, a solid is formed—it precipitates out of solution) Light and sound energy are produced

Nitric acid and copper produces gas bubbles and new color The copper of the Statue of Liberty has reacted with oxygen and acid (rain) creating a new green chemical. Combustion is defined as the burning of a fuel and oxidant to produce heat and/or work.

Precipitates: Solids form when 2 liquids are combined! Precipitate (Solution A + Solution B  Insoluble solid + solution D) Precipitates: Solids form when 2 liquids are combined!

CHEMICAL REACTIONS Chemical reactions are written as a chemical equation which identifies the reactants combined and the products created. Reactants are the substances that will be combined (THEY ARE THE “INGREDIENTS”) Products are the new substances that are formed after the reaction

Representation of chemicals and elements Elements are represented by chemical symbols, such as H for hydrogen and O for oxygen (the symbols are used on periodic table of elements) A chemical formula is used to represent a compound. For example, H2O represents water and C6H12O6 represents glucose. A compound is a substance made up of atoms of two or more different elements joined by chemical bonds.

CHEMICAL PROPERTIES THE ABILITY FOR A SUBSTANCE TO GO THROUGH A CHEMICAL REACTION

FLAMMABILITY

Reaction with an Acid Reaction with oxygen (oxidation)

Reaction with a Base

Reaction with Water

Oxidation (rusting)

Reaction with Light (bleaching)

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CHEMICAL REACTIONS Chemical formulas are used to represent the reactants and products in a chemical reaction. For example: CuSO4 + Fe  FeSO4 + Cu + heat (Reactants)  (products) When writing a chemical equation, the reactants are always on the left of the arrow. The products are always on the right. An arrow is used to show that a change has occurred. (It’s read as “changes to”)

LAW OF CONSERVATION OF MASS This states that, in a closed system, the mass of the products in a chemical reaction is the same as the mass of reactants in that reaction. Mass of reactants = mass of products. All of the atoms contained in the reactants will be present in the atoms of the products (what “goes in” must “come out”)

A “closed system” means that matter can not get in or out of the system. An example is a sealed can of vegetables. For example: if you performed a chemical reaction between an iron and oxygen, it may look like this: 4Fe + 3O2 --> 2Fe2O3 Notice that all atoms of Fe and O are the same on left as the right