3 Pure SubstancesPure substance – matter that always has exactly the same compositionTable salt and table sugar are two examples of pure substances.Substances can be classified into two categories—elements and compounds.
4 ElementsElement – a substance that cannot be broken down into simpler substancesAn element has a fixed composition because it contains only one type of atomExamples: The elements oxygen and nitrogen are the main gases in the air you breathe.
5 ElementsChemists use symbols of one or two letters to represent elements. The first letter is always capitalized. If there is a second letter, it is not capitalized.C represents carbon.Al represents aluminum.Au represents gold.
6 CompoundsCompound – a substance that is made from two or more simpler substances and can be broken down into those simpler substancesEx. – Water is composed of the elements hydrogen and oxygen. Oxygen and hydrogen are gases at room temperature, but water is a liquid.
7 MixturesHeterogeneous mixture – the parts of the mixture are noticeably different from one anotherThe sand is a heterogeneous mixture of different kinds of grains.
8 MixturesHomogeneous mixture – the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from anotherThe spoon is stainless steel, a homogeneous mixture of iron, chromium, and nickel.
9 SolutionsSolution – The mixture that forms when substances dissolve and form a homogeneous mixture
11 Matter – anything that has mass and volume Properties – characteristics of matterEx. – Color, odor, shape, texture, and hardness
12 Mass – The amount of matter in an object The mass of an object does not change unless some matter is either added to or removed from an object
13 Weight – response of mass to the pull of gravity Gravity – force of attraction between all objects in the universe
14 Volume – the amount of space an object takes up Measured in liters (L), milliliters (mL), and cubic centimeters (cm3)1 L = 1000 mL or 1000 cm3______ mL = 3.5 L3500 mL = 3.5 L
15 Densities of Some Common Substances Density – the mass per unit volume of an objectDensities of Some Common SubstancesSubstancesDensity (g/cm3)Air0.0013Gasoline0.7Wood (oak)0.85Water (ice)0.92Water (liquid)1.0Aluminum2.7Steel7.8Silver10.5Lead11.3Mercury13.5Gold19.3
17 Phase – state in which matter can exist: solid, liquid, gas or plasma
18 Sodium Chloride (Table Salt) Solid – matter with a definite shape and a definite volumeCrystal – solid in which the particles are arranged in a regular, repeating patternQuartzSodium Chloride (Table Salt)
19 Amorphous solid – solid that loses its shape under certain conditions Sealing Wax
20 Liquid – matter with no definite shape but with a definite volume Viscosity – the resistance of a liquid to flowHoney has a higher viscosity than water
21 Gas – matter with no definite shape or volume Plasma – high-energy phase of matterPlasma is one of the most common phases of matter in the universe
23 Solid-Liquid Phase Changes Melting – the change of a solid to a liquidMelting point – the temperature at which a solid changes to a liquid
24 Solid-Liquid Phase Changes Freezing – the change of a liquid to a solidFreezing point – the temperature at which a liquid changes to a solidThe freezing point of a substance is equal to its melting point
25 Liquid-Gas Phase Changes Vaporization – the change of a substance from a liquid to a gasEvaporation – vaporization at the surface of a liquid
26 Liquid-Gas Phase Changes Boiling – the process in which particles inside a liquid as well as those on the surface change to a gas
27 Liquid-Gas Phase Changes Boiling point – temperature at which a substance changes from the liquid phase to the gas phaseBoiling point of water – 100 degrees CelsiusBoling point of a diamond – 4200 degrees Celsius
28 Liquid-Gas Phase Changes At high altitudes, air pressure is lower, so the boiling point is reduced.Water will boil at a temperature lower than 100 degrees Celsius at high altitudes
29 Liquid-Gas Phase Changes Condensation – the change of a gas to a liquidWater vapor in the surrounding air loses heat energy when it comes in contact with the cold glassWater vapor condenses and becomes liquid
30 Solid-Gas Phase Changes Sublimation – the surface particles of a solid escape directly into the gas phaseEx. – snow turns to water vaporEx. – dry ice
31 Heat, Temperature, and Phase Changes Heat is energy that causes the particles of matter to move faster and farther apart. As the particles move faster, they leave one phase and pass into another.
33 Observing Chemical Properties Chemical property – any ability to produce a change in the composition of matter
34 Observing Chemical Properties Two chemical properties:Flammability – a material’s ability to burn in the presence of oxygenReactivity – The property that describes how readily a substance combines chemically with other substancesIron + Oxygen = Rust
35 Chemical ChangesChemical changes – the changes that substances undergo when they change into new and different substances
36 Chemical ChangesA change in color is a clue that a chemical change has produced at least one new substance (most of the time)As a match burns, it shrivels up and turns black.
37 Physical PropertyPhysical property can be observed with senses and can be determined without destroying matter
38 Physical ChangesPhysical change – a change in size, shape, or state of a substance but no new substance is formed