Chapter 2: Energy and Matter

Chapter 2:Energy and Matter “Does energy really matter?” Sept. 2006

Chapt. 2 Objectives • Learn the three basic forms of energy. • State the “Law of Conservation of Energy.” • Compare Fahrenheit, Celsius & Kelvin temperature scales. • Explain what is meant by “Absolute Zero.” • Name & describe the four states of matter. • Compare the physical & chemical properties of matter. • State the “Law of Conservation of Matter.” • Explain the difference between elements & compounds. • Compare homogeneous and heterogeneous mixtures. • Describe techniques to separate mixtures.

2-1 ENERGY • Energy is the capacity to do work or to produce heat. • Forms of energy • Kinetic (motion) • Potential (position, gravity, chemical, electrical) • Radiant (infrared, ultraviolet, X-rays)

Measuring Energy One calorie = Energy needed to raise 1 gram water by 1 degree Celsius • 1,000. calories = 1 Calorie (food) • 1.00 calorie = 4.182 Joules

Law of Conservation of Energy • States that… • In any process, energy is neither created nor destroyed, but… • …energy may be converted into other forms. (Can you give any examples?)

2-2 TEMPERATURE • Heat and temperature are not the same! • Heat is a form of energy. • Temperature is a measure of heat energy. • Thermometers (invented by Galileo) measure temperature. • Fahrenheit, Celsius or Kelvin scale? • SI scale is the kelvin (K) scale (no ° sign) • 1°C = 1 K • K = °C + 273 • Water freezes at 273 K & boils at 373 K • Zero kelvin is known as “Absolute Zero.”

What happens as energy is removed from matter? • Consider steam (water vapor) at 150°C (or 423 kelvins): • First it becomes a liquid (water). (100°C or 373 K) • Water particles slow down & get closer together. • Liquid water continues to cool as energy is removed. • Water particles continue to slow down. • Eventually it freezes to a solid (ice). (0°C or 273 K) • Same thing continues to occur as more kinetic energy is lost. • But as more energy is removed, what happens? • Temperature drops more, well below 0°C (or 273 K). • Particles move more slowly (losing kinetic energy) until… • …at -273°C (or 0 K) motion stops! (Zero kinetic energy!) • Zero kelvin is known as “Absolute Zero.”

Absolute Zero • Zero kelvin or -273°C • The temperature at which all motion theoretically ceases. • Material at 0 K would have NO kinetic energy. • Zero kelvin has not been reached, but scientists have come very close to it. • Materials have very unusual properties at Absolute Zero!

Problems • Sheets 2-2A, 2-2PP, 2-2RR

2-3 What is “Matter”? • “Matter” is anything that has mass and volume (that is, it takes up space).

Categories to Consider • Matter • Not Matter • Not Sure Words will appear on the slide. You decide the category to which they belong, and write it in your notebook (left side).

The List • Soda Can • Water • Fish • Garbage • Time • Motion • Computer • Carbon Dioxide Gas • The Middle of a Full Balloon • An Idea • Tree • Energy Jump Ahead

Mass • The quantity of matter in an object. • Measured in kilograms, kg (SI unit). • Also measured in grams, g, for convenience in chemistry labs. • Exactly 1,000 grams = 1 kilogram. • A “Balance” measures mass, but a “Scale” measures weight. (What’s the difference?)

Weight • The effect of gravity on an object. • An object may be weightless, but it always has mass. • If you were hit by a moving brick while you were deep in outer space, it would still hurt!

Volume • A derived unit that measures the amount of space an object occupies. • Measured in cubic meters (m3 is SI Unit), but Liters (L) and milliliters (mL) are more commonly used in chemistry lab. • 1 cm3 = 1 mL • Exactly 1000 mL = 1 L.

Properties of Matter • Electrical Conductivity - ability to carry an electrical current. (Copper) • Heat Conductivity - ability to transfer thermal energy. (Steel) • Density - “mass-to-volume ratio”; how tightly matter is packed. (Cement is very dense; air is not.) • Melting Point – solid-to-liquid (or liquid-to-solid) change; same as freezing point.

Properties of Matter (cont) • Boiling Point – liquid-to-gas (or gas-to-liquid change); same as condensation point. • Malleability – able to be hammered, rolled or beaten into thin sheets. (Aluminum foil) • Ductility - ability to be drawn into a wire. (Copper, tungsten)

Physical Can be observed without changing the identity of the substance. Boiling & all phase changes, color, temperature, size. Chemical Involve changing the substance into a new substance. Flammability, rusting, digesting, aging. Properties of Matter (cont)

Intensive – a property that does not depend upon how much you have. Flammability, color, hardness, crystal shape, temperature. Extensive– a property that does depend upon how much you have. Volume, mass, height, weight. Intensive vs. Extensive Properties

Problem • “Observing a Candle” Experiment. • Follow the procedure on page 70 very carefully. • Be sure to list the physical & chemical properties of the candle (before, during & after the experiment). • Record as many observations as you can! • Note Part 5.

Class Activity: Sorting Materials • Sort 20 materials listed on signs. • Column A has oxygen & neon. • Column B has apple & sand. • Where does iron go? • Where does water go? • Continue sorting the rest. • What are your criteria? • What definitions can we derive from this?

Pure Substances vs. Mixtures • A pure substance is matter that is uniform, has unique chemical and physical properties, and has a definite composition. • Elements • Compounds • A mixture is a blend of two or more pure substances that are not chemically combined. • Homogeneous Mixtures • Heterogeneous Mixtures

Elements • An element is a substance that cannot be separated into simpler substances by a chemicalchange. • An atom is the smallest particle of an element that retains the chemical identity of that element. • Element names are logical, often named after locations, discoverers or historical roots (Latin, German etc.). • Over 110 elements; only 92 occur in nature. • Chemists use symbols to abbreviate element names. • Written with one capital letter and possibly one lower case letter. • Example: “CONI” differs from CoNi, CONi, CoNI. (Why?)

Elements to Learn You must learn the names and correct chemical symbol for Elements 1 to 20 of the Periodic Table. Also know Cr, Mn, Fe, Cu, Zn, Br, Kr, Ag, Sn, I, Xe, Au, Hg, Pb, W. • Be able to give the name from the symbol and the symbol from the name. • Practice and test yourself! (Flash cards?)

Elements vs. Compounds Recall that an element is a substance that cannot be separated into simpler substances by a chemicalchange. But a compound is a substance containing two or more differentelements combined in a fixed ratio. Examples: H20 and AlCl3

Mixtures • A mixture is a blend of two or more pure substances that are not chemically combined. • Heterogeneous mixtures have visibly different parts. • EXAMPLES? • Oatmeal raisin cookies, salad dressing • Homogeneous mixtures do not contain visibly different parts. • EXAMPLES? • Salt water, air

CLASSIFICATION OF MATTER MATTER MIXTURE Two or more substances not chemically combined. PURE SUBSTANCE HETEROGENEOUS ELEMENTS HOMOGENEOUS COMPOUNDS

CLASSIFICATION OF MATTER MATTER NO YES Separate by physical means? MIXTURE Two or more substances not chemically combined. PURE SUBSTANCE NO YES YES NO Uniform Composition? Decompose by chemistry? HETEROGENEOUS HOMOGENEOUS ELEMENTS COMPOUNDS

Problem • How would you separate a sample of sandy sea water from Surf City into all of its components? • Devise a scheme in your notebook.

Separating Mixtures • Filtration • Example: making coffee • Distillation • Example: boiling water • Crystallization • Example: Salt Flats, UT • Chromatography • Example: ink running when wet

Did we meet the Chapt. 2 Objectives? • Learn the three basic forms of energy. • State the “Law of Conservation of Energy.” • Compare Fahrenheit, Celsius & Kelvin temperature scales. • Explain what is meant by “Absolute Zero.” • Name & describe the four states of matter. • Compare the physical & chemical properties of matter. • State the “Law of Conservation of Matter.” • Explain the difference between elements & compounds. • Compare homogeneous and heterogeneous mixtures. • Describe techniques to separate mixtures.

Chapter 2: Energy and Matter