Matter I. What is Matter?

Matter Anything that has mass and takes up space

A. Kinetic Molecular Theory KMT Particles of matter are always in motion. The kinetic energy (speed) of these particles increases as temperature increases.

B. Pure Substances Element composed of identical atoms Atom is the smallest unit of element that maintains the properties of the element EX: copper wire, aluminum foil

B. Pure Substances Compound composed of 2 or more elements in a fixed ratio properties differ from those of individual elements EX: table salt (NaCl)

B. Pure Substances Compound Every compound is different from the elements it contains Atoms can join together to make molecules like letters of the alphabet combine to form different words

B. Pure Substances Chemical Formulas Shows how many atoms of each element are in a unit of a substance The subscripts (little numbers on the bottom) tell you how many atoms of each are present Sugar has 6 Carbon atoms, 12 Hydrogen atoms, and 6 oxygen atoms

B. Pure Substances Law of Definite Composition A given compound always contains the same, fixed ratio of elements. Law of Multiple Proportions Elements can combine in different ratios to form different compounds.

Two different compounds, each has a definite composition. B. Pure Substances For example… Two different compounds, each has a definite composition.

C. Mixtures Variable combination of 2 or more pure substances. Heterogeneous Homogeneous

C. Mixtures particles don’t settle EX: rubbing alcohol, sugar water Solution homogeneous very small particles particles don’t settle EX: rubbing alcohol, sugar water

C. Mixtures particles DO settle EX: flour and water Solution heterogeneous Substances are not evenly distributed or uniform particles DO settle EX: flour and water

Can it be physically separated? A. Matter Flowchart MATTER yes no Can it be physically separated? MIXTURE PURE SUBSTANCE Is the composition uniform? no yes Can it be chemically decomposed? no yes Homogeneous Mixture Heterogeneous Mixture Compound Element Colloids Suspensions

C. Mixtures Examples: element graphite hetero. mixture pepper compound Homogenous mixture Examples: graphite pepper sugar (sucrose) paint soda

C. Mixtures Liquids can either be miscible or immiscible Miscible Homogenous Only looks like one liquid when combined Ex. Gas (really about 100 liquids) Immiscible Heterogeneous Liquids don’t mix and they form layers Ex. Oil in water; italian salad dressing

B. Density A measure of mass per unit of volume, remains constant for pure substances How much matter is contained in a certain volume The higher the object’s density, the higher its mass per volume. This is what decides if something floats or sink… If you have to substances, the one with the larger density will sink and the one with the smaller density will float SI Unit: kg/m3 Common units in problems: g/mL, g/cm3

B. Density M Mass (g) D V Volume (cm3)

Problem-Solving Steps 1. Analyze 2. Plan 3. Compute 4. Evaluate

B. Density V = 825 cm3 M = DV D = 13.6 g/cm3 M = (13.6 g/cm3)(825cm3) An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass. GIVEN: V = 825 cm3 D = 13.6 g/cm3 M = ? WORK: M = DV M = (13.6 g/cm3)(825cm3) M = 11,200 g

B. Density D = 0.87 g/mL V = M V = ? M = 25 g V = 25 g 0.87 g/mL A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid? GIVEN: D = 0.87 g/mL V = ? M = 25 g WORK: V = M D V = 25 g 0.87 g/mL V = 29 mL

II. Properties & Changes in Matter Physical vs. Chemical

A. Physical vs. Chemical Properties Physical Property can be observed or measured without changing the identity of the substance Chemical Property describes the ability of a substance to undergo changes in identity

A. Physical vs. Chemical Examples: physical melting point chemical flammable density magnetic tarnishes in air reactivity

More examples of chemical and physical properties Melting pt Boiling pt Freezing pt Density (mass, vol.) Buoyancy Color Texture Change in Physical State (solid, liquid, gas, plasma) Reactivity Fermentation Flammability Oxidation pH Toxicity electronegativity

C. Physical vs. Chemical Changes Physical Change changes the form of a substance without changing its identity properties remain the same Chemical Change changes the identity of a substance products have different properties

C. Physical vs. Chemical Changes Signs of a Chemical Change- How you know if a reaction occurred… change in color or odor formation of a gas formation of a precipitate (solid) change in light or heat

C. Physical vs. Chemical Changes Examples: rusting iron dissolving in water burning a log melting ice grinding spices chemical physical

Quick Summary of Physical and Chemical Changes Physical changes are changes in the physical properties of a substance that do not change the identity of a substance Physical changes are often easily reversed Chemical Changes form new substances that have new properties. Chemical changes can be reversed ONLY through chemical reactions Chemical changes often cause changes in color, smell, or produce sound, light, odor, heat