2 Overview Learn about the composition of matter Learn the difference between elements and compoundsDistinguish between physical and chemical properties and changesDistinguish between mixtures and pure substancesLearn 2 methods of separating mixtures
3 Did you ever wonder?... How do plants grow & why are they green? Why is the sun hot?Why does a hot dog get hot in a microwave?Why does wood burn and rocks do not?How does soap work?Why does pop fizz?What’s happening when iron rusts?Why doesn’t aluminum foil rust?How does a hair permanent work?
4 The Particulate Nature of Matter Matter: the “stuff” the universe is composed ofHas mass and occupies spaceComes in many forms: the stars, your chair, brain tissueComposed of tiny particles called atomsScanning tunneling microscope produces images of atomsCan’t see with naked eye, similar to looking at beach from far away; can only see sand particles when you get close
5 Elements and Compounds Atoms: all matter is composed of these tiny particlesOver 100 different atomsSimilar to words, all made from 26 different lettersAll matter made from about 100 different atomsCompounds: substances made by bonding atoms together in specific waysContain 2 or more different types of atomsSame throughoutMolecule: made up of atoms that are “stuck” together
7 ElementsSome atoms can combine with like atoms to form molecules: H2 & O2Carbon bonds forming large groupsElements: substances that contain only one type of atomCompound: always contains atoms of different elements (water = H2O)
13 Figure 2. 7: The three states of water: Solid Figure 2.7: The three states of water: Solid. Solids: Rigid; have a fixed shape and volume
14 Figure 2.7: The three states of water: Liquid Liquid: has a definite volume but takes the shape of its container
15 Figure 2. 7: The three states of water: Gas Figure 2.7: The three states of water: Gas. Gas: has no fixed volume or shape; uniformly fills any container
16 Physical and Chemical Properties and Changes Physical Properties: Odor, color, volume, state, density, melting point, and boiling pointChemical properties: refer to a substances ability to form new substancesExamples: wood burning, rusting of steel, digestion of food, growth of grassGiven substance changes to a fundamentally different substance or substances
17 Chemical vs. Physical change in water Physical changessolid → liquid → gasChange of state: H2O molecules still presentChemical change = electrolysiswater changed into different substances (water decomposes to hydrogen & oxygen)
18 Electrolysis, the decomposition of water by an electric current, is a chemical process.
19 Physical & Chemical Changes Physical change involves a change in one or more physical properties, but no change in fundamental components of substance. Most common are changes in state.Chemical change involves a change in the fundamental components of the substance. Chemical changes are called reactions.
20 Mixtures and Pure Substances Mixture: something that has variable compositionExamples: soda, coffee, tap water, airComposition of mixtures varies, but composition of compounds is always the sameComposition depends on how much of each component is used when mixture is formedCan be separated into pure substances: elements and/or compounds
23 Mixtures: Alloys Alloys: mixtures of metals Many gold alloys: mixture of gold, copper, and silverThey are not compounds! (like water)Composition varies
24 Figure 2.10: Twenty-four-karat gold is an element Eighteen-karat gold is an alloy Fourteen-karat gold is an alloy.
25 Homogeneous and Heterogeneous Homogeneous mixture is the same throughout, & also called a solutionExamples: salt water, air, brass (mixture of copper and zinc)Heterogeneous mixture contains regions that have different properties from other regionsExamples: sand/water mixture, rocky road ice cream, chocolate chip cookie dough
27 Distillation: Separation Process Boil water (or other liquid)Vaporizes (turns into gas = steam)Condense (cool steam in tube) – turns back to liquidMinerals are left behindPure water collectedPhysical change
28 The solution is boiled and steam is driven off.