What are we really studying here anyway?

 The study of the structure of matter and the changes that it undergoes  Matter – anything which occupies space and has mass

Physical Properties - a quality of a substance that can be observed or measured without changing the composition of the substance

 Chemical Properties ◦ The ability of a substance to undergo chemical reactions to form new substances

1.Physical 2. Chemical Changes in Matter

Physical Changes -Any change in a property of matter that does not result in a change in identity -No new stuff formed -Typically reversible Examples: Melting Freezing Boiling Evaporation Condensation Sublimation Deposition Dissolving

Chemical Changes -Any change in which one or more substances are converted into different substances with different characteristics -Referred to as chemical reaction -Starting materials called reactants -Resulting materials called products Reactants → Products “yields”

Chemical Changes -During chemical reactions atoms are rearranged in different combinations -Law of Conservation of Mass – the products of a reaction must have the same total mass as the reactants that formed them

How do we know when a Chemical Change has taken place? -Color change -Odor change -Energy change (typically heat change) -Endothermic – energy is taken in - surroundings get cooler -Exothermic – energy is given off - surrounding get warmer -Gas or solid produced -Precipitate – a solid that forms from the mixing of 2 solutionsPrecipitate

Matter Pure Substances Mixtures Heterogeneous Homogeneous Compounds Elements

Types of Matter Mixtures Def: a combination of two or more substances each which retain their own properties -Can be separated by physical means

 Definition:  the composition of the mixture varies throughout the sample - can see different components (phases) - Ex) soil, concrete

 the composition and properties are the same throughout the mixture (uniform) - also called solutions - substances dissolved in water have (aq) following their formula Ex) NaCl (aq), brass, air

 Filtration  Evaporation  Distillation  Chromatography  Magnets

 Def: any variety of matter that has the same properties and composition throughout the sample  Types: ◦ Elements ◦ Compounds

 Def: simplest form of matter - Cannot be broken down by normal chemical change Atoms – smallest particle of an element that retains the properties of that element Zoom in

 shorthand way of identifying an element  First letter of symbol always capitalized, second letter never capitalized  Some symbols taken from Latin names for element  Ex) Sodium – Na for name natrium

 Most elements are monatomic  Meaning they are found in nature as single uncombined atoms (like the silicon before)  7 elements are diatomic in nature (found as pairs of atoms linked together, molecules) H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2

Metals – left of “staircase” General Properties: good conductors of heat and electricity, ductile, malleable, luster, high MP, lose electrons in reactions

Nonmetals – right of “staircase” General Properties: poor conductors solids are brittle gain electrons in reactions

 Metalloids – (6) found along the “staircase” General Properties: show properties of metals and nonmetals B = Boron Si = Silicon Ge= Germanium As= Arsenic Sb= Antimony Te= Tellurium

 Noble Gases – Group 18 General Properties: nonreactive monatomic gases

Def: substances made up of 2 or more elements chemically combined in a definite ratio - Can be decomposed by a chemical change (heat, electricity)decomposed  Ex) NaCl – sodium chloride  MgO – magnesium oxide  NH 4 – ammonia  CH 4 – methane

 Molecules – individual particles of compounds, which exhibit properties of the compound  Binary compounds – compounds that consist only of 2 different elements Zoom in

– A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or the source. Ex) Table Sugar is called sucrose and is composed of 42.1% C, 51.4 % O, 6.5 % H

 Def: the ability to cause change or do work Types of Energy 1. Thermal total amount of internal energy an object has, related to the motion of the particles that make up the substance

2. Chemical – energy associated with chemical change, stored in chemical bonds 3. Electrical – associated with moving charged particles 4. Electromagnetic (light) – energy of electromagnetic radiation

5. Nuclear – associated with the changes in mass of atomic nucleiNuclear

– Energy may be changed from one form to another transferred from one form to another or one body to another but the total amount of energy remains constant - Energy in = Energy out