Chemical vs physical properties

State of matter (solid, liquid, gas) Melting, freezing, boiling point Elements and compounds can be described by their chemical and physical properties Physical property: characteristic of a substance you can observe (using your senses) without changing it into something else State of matter (solid, liquid, gas) Melting, freezing, boiling point Magnetism Density Color Shape Malleability Solubility Specific heat

Chemical properties: properties of an element or compound in a chemical reaction pH Reactivity Flammability/Combustion Rusting Bond

Practice on Identifying Chemical and Physical Properties Water boils at 100 degrees Celsius. Diamonds are capable of cutting glass. Water can be separated by electrolysis into hydrogen and oxygen. Sugar is capable of dissolving in water. Vinegar will react with baking soda. Yeast acts on sugar to form carbon dioxide and ethanol. Wood is flammable. Aluminum has a low density. Ammonia is a gas at room temperature. Bromine has a red color.

Most types of matter heat up at the same rate Which of the following conclusions can be drawn from the information shown? Most types of matter heat up at the same rate Most types of matter cool at the same rate It takes less energy to heat 1g of silver than 1g of gold It takes more energy to heat 1g of water than 1g of copper Material Specific Heat Aluminum 0.899 Copper 0.387 Gold 0.129 Silver 0.234 Water 4.182 Wood 0.176

Magnesium melts at 650°C. If a 100g sample of magnesium melts at 650°C, then a 75g sample would melt at: 325°C 650°C 487.5°C 162.5°C

Chemical change: atoms are rearranged, I have different substances at the end of a chemical reaction/change Change in color Formation of precipitate (L+LS) Formation of a gas Creation of light Burning Change in temperature (exothermic, endothermic)

Changes can be physical or chemical Physical changes do not rearrange atoms, I have the same substance I started with. I can reverse a physical change Change in shape Change in phase Dissolving Reversable

Practice on Identifying Chemical and Physical Changes Dry ice, solid carbon dioxide, is sublimed at room temperature. Salt is dissolved in water. Iron rusts in a damp environment. Gasoline burns in the presence of oxygen. Hydrogen peroxide decomposes to water and oxygen.

Combustion: reacting with oxygen frequently producting CO2& water C3OH + O2  CO2 + H2O + heat 2Mg + O2  2MgO + Heat ______________________________________ 2H2 + O2  2H2O + heat NH4 + NO2  N2O + H2O

Compounds or molecules are represented using a chemical formula Subscripts (little number) tell you the number of atoms in the 1 molecule of the compound Coefficients (big number out front) tell you how many molecules (no number means the number is 1!)

Calculate the number of atoms of each element AgMnO4 AlBO2 CH3OH BaSi2O5

Calculate the total number of atoms of each element 2AgMnO4 6AlBO2 7CH3OH 2BaSi2O5 KNO3

Conservation of Mass Mass on the reactant side of the equation equals the mass on the product side of the equation Number and type of atoms on the reactant side of the equation equals the number and type of atoms on the product side of the equation. Reactants Products

To check for balance, multiply coefficient x subscript __H₂ + __O₂  __H₂O A. 1, 1, 1 B. 2, 1, 2 C. 2, 1, 2 D. 2, 2, 2 __K + __B2O3  __K2O + __B A. 3, 2, 3, 2 B. 6, 1, 3, 2 C. 6, 2, 3, 2 3, 2, 2, 2 To balance an equation its cool to change coefficients, do not change subscripts….don’t mess w/the little people (you’ll change the molecule’s identity!)

Calculate the mass of the product of 6. 40 g of magnesium with 1 Calculate the mass of the product of 6.40 g of magnesium with 1.32 g of oxygen . Calculate the mass of the zinc that reacts with 4.11 g of hydrochloric acid to form 9.1 g of zinc chloride and 3.97 g of hydrogen gas. During the combustion of 5.00 g of Butane in the presence of oxygen, 4.01 g of carbon dioxide and 3.55 g of water is given off. How much oxygen was needed to totally combust the butane?

Review…..

Compound: Made when two or more elements combine during a chemical reaction Examples: Water Salt Sugar Chemical Change

Compounds are formed or separated through chemical reactions… What is evidence that a chemical reaction is happening again? Fire, Combustion, Explosion A new color appears/disappears Temperature change Production of Gas, gas bubbles Production of Precipitates

Mixture Combines 2 or more substances without producing a chemical reaction NOT the same throughout - heterogeneous Can be separated easily Examples: Soil Fruit salad Physical Change

Solution: A type of MIXTURE that IS the same throughout - homogenous Solute- substance being dissolved Solvent- substance doing the dissolving Examples: Salt water Lemonade Physical Change Salt = Solute Water= Solvent Salt Water= Solution