The Study of Matter and Energy CHEMISTRY The Study of Matter and Energy

I. Chemistry: Definition: the branch of science that deals with the study of matter, energy, and their interaction. a) Matter: defined as anything that has mass and occupies volume. Mass – is the measurement of the amount of matter in an object OR is the quantity of matter an object has. The fundamental unit for mass is the gram (g). The instrument used in chemistry to measure the mass of an object is the triple beam balance or the digital scale.

Figure 1: Triple Beam Balance From: http://www.kirkwood.k12.mo.us/parent_student/khs/BartinJ/sci%20skills%20book/using_a_3beam_bal.jpg

From: http://www.electrickiva.com/quiz/exam03/meniscus.gif Volume: defined as the amount of space an object occupies. The fundamental unit for volume is the liter (l). Other units used to measure the volume of substances include the cubic centimeter (cm3) or the (cc). The instrument used in chemistry to measure the volume of a substance is the graduated cylinder. Fig 2: Graduated Cylinder showing the meniscus From: http://www.electrickiva.com/quiz/exam03/meniscus.gif

b) The States of Matter: Gases, liquids and solids are all made up of microscopic particles, but the behaviors of these particles differ in the three phases. 1. SOLID: state of matter that has BOTH A DEFINITE VOLUME and a DEFINITE SHAPE.  Fig 3: Arrangement of Particles in a Solid From: http://www.ul.ie/~walshem/fyp/solid.gif

Fig. 4: Arrangement of Particles in a Liquid  2. LIQUID – state of matter that has DEFINITE VOLUME but NO DEFINITE SHAPE.  A key property of a liquid is that they FLOW and can be POURED. Fig. 4: Arrangement of Particles in a Liquid From: http://www.ul.ie/~walshem/fyp/states%20of%20matter.htm#liquid

From :http://www.ul.ie/~walshem/fyp/gas.gif 3. GAS – state of matter that has NO DEFINITE VOLUME and NO DEFINITE SHAPE.  A Gas ALWAYS TAKES BOTH THE VOLUME AND THE SHAPE OF ANY CONTAINER INTO WHICH IT IS PLACED.  If a gas is NOT in a container, it will spread out as far as it can. Fig. 5: Arrangement of Particles in a Gas From :http://www.ul.ie/~walshem/fyp/gas.gif

Ex: #1 Under the same conditions of temperature and pressure, a liquid differs from a gas because the particles of the liquid: a) are in constant straight-line motion b) take the shape of the container they occupy c) have no regular arrangement d) have stronger forces of attraction between them

II. The Classification of Matter a) Substances: Elements and Compounds 1. ELEMENTS ARE PURE (homogeneous) SUBSTANCES THAT CANNOT BE BROKEN DOWN (decomposed) CHEMICALLY INTO SIMPLER KINDS OF MATTER. More than 100 elements have been identified, though Fewer than 30 are Important in Living Things.  All of the Elements are arranged on a Chart known as THE PERIODIC TABLE.  Among the information provided in The Periodic Table are the ATOMIC NUMBER, THE CHEMICAL SYMBOL, AND THE ATOMIC MASS FOR EACH ELEMENT.

Figure 12: Atomic Mass, Number, and Chemical Symbol More than 90 Percent of the Mass of living things is composed of JUST FOUR ELEMENTS:  OXYGEN, O, CARBON, C, HYDROGEN, H, AND NITROGEN, N. Each Element has different Chemical Symbol which consist of One or Two Letters. Figure 12: Atomic Mass, Number, and Chemical Symbol

2. Compounds: Substances that consist of two or more elements that are combined chemically by bonds. The elements in a compound can only be separated chemically by breaking the bonds that hold them together. Compounds have fixed ratios of their components. Water will always have 2 hydrogen atoms for every one oxygen atom. Compounds are homogeneous – one cannot distinguish between the components of the compound. If given a sample of water, you could not determine what is hydrogen and what is oxygen. Examples of Compounds water carbon dioxide glucose

Two or more substances that are combined physically; the components can be easily separated. b) Mixtures In homogeneous mixtures, the substances are completely mixed. This means that you cannot see the individual components. The mixture appears to be only one substance. In heterogeneous mixtures, the substances are not completely mixed. This means that you can see the individual components. The mixture appears to be only two different substances in the same container. Figure 14: Heterogeneous Mixture: SOIL Figure 13: Homogeneous Mixture: Salt Water

III. Energy: a) Definition: The capacity for doing work. b) Energy has several forms including: potential energy - the energy stored in the chemical bonds that exist between particles of matter. kinetic energy – the energy of motion. Temperature is a direct measure of the average kinetic energy of particles. c) Law of Conservation of Mass and Energy: This scientific law states that neither mass nor energy can be created or destroyed. They can only be converted from one form into another. Units: Joule (J) or Kilojoules (KJ), calorie (cal) or Kilocalorie (Kcal).

d) Types of Energy Light Energy: the energy associated with light waves and other forms of electromagnetic radiation. Electrical Energy: the energy associated with electrical current (flow of electrons). Chemical energy: the energy associated with chemical changes (the breaking and reformation of chemical bonds). Heat Energy: the energy associated with the temperature of substances. Heat energy is the least useful form of energy. Mechanical Energy: the energy associated with doing work. Atomic and Nuclear Energy: the energy associated with changes in the mass of atoms and the energy that binds atoms together.

A compound differs from a mixture in that a compound always has a Ex: #5 A compound differs from a mixture in that a compound always has a a) homogeneous composition b) maximum of two components c) minimum of three components d) heterogeneous composition Ex: #6 Which substance cannot be decomposed into simpler substances? a) ammonia (NH3) b) aluminum (Al) c) methane (CH4) d) methanol (CH3OH)

e) Energy and Chemical Change All chemical reactions require energy to occur. Chemical bonds are forces of attraction that hold atoms, elements, compounds, and molecules together. Chemical bonds store energy. For a reaction to occur, a chemical must absorb enough energy to break the bonds that hold it’s atoms together. The amount of energy that must be absorbed by a chemical to begin a reaction is called the Activation Energy (Ea).

IV. Free Energy and Spontaneity a) Spontaneous Reactions: chemical reactions that occur without the addition of an outside source of energy. b) Non-spontaneous Reactions : chemical reactions that require an external energy source to occur.

Ex: The burning (oxidation or combustion) of gasoline.                                                                                                                                                 V. Types of Reactions Exothermic Reactions Energy releasing processes, ones that "generate" energy, are termed exothermic reactions. Figure 6 Ex: The burning (oxidation or combustion) of gasoline.

Figure 7: Exothermic Reaction

b) Endothermic Reactions: Reactions that require energy to initiate the reaction are known as endothermic reactions. Figure 8: Endothermic Reaction Ex: The melting of ice.

NOTE: Enthalpy (H) indicates whether a reaction is exothermic or endothermic. If DH = (+), the reaction is endothermic and energy is absorbed. If DH =(-), the reaction is exothermic and energy is released.

Note: All natural processes tend to proceed in such a direction that the disorder or randomness of the universe increases. Endergonic = Endothermic Exergonic = Exothermic

Label the following diagram and indicate what each arrow stands for.

VI. Measuring Energy a) Temperature Temperature is a measure of the average kinetic energy of matter. The greater the average kinetic energy, the greater the velocity of the particles of matter, the greater the temperature (and vice versa). The instrument used to measure the temperature (average kinetic energy) of matter is the thermometer.

1. Thermometer: A thin glass, capillary tube that contains a fluid (mercury (Hg)) that when heated will expand. When the fluid expands, it rises. This correlates to an increase in temperature. 2. Temperature Scales: There are several scales that are used to represent the temperature of substances. They include: Fahrenheit, Celsius, and Kelvin. Scientists most frequently use the Celsius and Kelvin scales.

212° 100 ° 373 Boiling Point 32 ° 0 ° 273 Freezing Point Absolute Zero Fahrenheit Celsius Kelvin Figure 9: Temperature Scales and the Boiling/Freezing Points of Water at Standard Conditions

Ex: #2 As ice cools from 273 K to 263 K, the average kinetic energy of its molecules will: a) decrease b) increase c) remain the same

Conversion Formulas: C = Celsius K = Kelvin 1. C = K – 273 2. K = C + 273 Ex: #3 What Kelvin temperature is equal to 25°C? a) 248 K b) 298 K c) 100 K d) 200 K

VII. Heating/Cooling Curves Heating/Cooling curves shows the change in kinetic and potential energies of substances. In addition, the curves indicates the points of phase change. a) Kinetic Energy: the energy associated with the velocity of the particles of matter. Temperature is a direct measure of the average kinetic energy of matter. As temperature increases, so does the average kinetic energy of matter (and vice versa). Note: During phase changes, the KE of matter remains the same. b) Potential Energy: the stored energy found within substances. The potential energy of a substance increases as it is converted to a phase of matter having greater entropy (and vice versa). Note: When KE changes, PE remains the same.

Figure 15: The Heating Curve of Water

Explanation of Figure 15 Point State Kinetic Energy Potential Energy A Solid Increases RTS B (s) to (l) melting RTS Increases C Liquid Increases RTS D (l ) to (g) boiling RTS Increases E Gas Increases RTS RTS = remains the same

c) Phase Changes Substances must either gain or lose energy for a change of phase to occur. Increase in Enthalpy (and Entropy) Process Solid to liquid Melting Liquid to gas Boiling (vaporization) Solid to gas Sublimation Decrease in Enthalpy (and Entropy) Process Gas to Liquid Condensation Liquid to solid Freezing Gas to solid Deposition