Ch. 3: Matter and EnergyCh. 3: Matter and Energy

Dr. Namphol Sinkaset

Chem 152: Introduction to General Chemistry

I. Chapter OutlineI. Chapter Outline

I. Introduction

II. Classifying Matter

III. Physical/Chemical Properties/Changes

IV. Conservation of Matter

V. Energy

VI. Temperature

VII. Heat Capacity

I. IntroductionI. Introduction

• Everything around you is composed of matter.

• Besides matter, energy is the other major component of our universe.

II. MatterII. Matter

• Matter is anything that occupies space and has mass.

• Some matter is easy to see (water, wood), others are difficult (air, dust).

• The most basic building block of matter is the atom.

II. Atoms and MoleculesII. Atoms and Molecules

• atoms: submicroscopic particles that are the fundamental building blocks of all matter.

• Sometimes, atoms are bonded together to form molecules.

• molecules: two or more atoms joined to one another in specific geometric arrangements.

II. Atomic and Molecular II. Atomic and Molecular MatterMatter

II. Actual Images of Atoms II. Actual Images of Atoms and Moleculesand Molecules

II. States of MatterII. States of Matter

• Matter can be classified by its state.• solid: closely-packed particles with fixed

locations• liquid: closely-packed particles, but free to

move around• gas: great distances between particles with

free movement

II. States of MatterII. States of Matter

II. The Solid StateII. The Solid State

II. Properties of Different StatesII. Properties of Different States

II. Pure Substances and II. Pure Substances and MixturesMixtures

• Matter can be classified by its composition.

• pure substance: matter composed of only one type of atom or molecule

• mixture: matter composed of two or more different types of atoms or molecules which may vary in proportion

II. ElementsII. Elements

• element: a pure substance that cannot be broken down into simpler substances

II. CompoundsII. Compounds

• compound: a pure substance composed of two or more elements in fixed definite proportions.

II. MixturesII. Mixtures• Most matter exists in this form.• heterogeneous: varied composition from one

region to another• homogeneous: uniform composition throughout

II. Classification by II. Classification by CompositionComposition

II. Sample ProblemII. Sample Problem

• Classify the following as a pure substance or mixture. Further classify them as an element, compound, homogeneous, or heterogeneous.a) blood

b) sugar

c) mercury in a thermometer

d) chicken noodle soup

III. Distinguishing MatterIII. Distinguishing Matter

• We use physical and chemical properties to tell the difference between samples of matter.

• physical property: a property a substance displays without changing its composition

• chemical property: a property a substance displays only by changing its composition

III. Boiling Point of WaterIII. Boiling Point of Water

• At the boiling point, water is converted to steam, but steam is just a different form of water.

III. An Iron Nail RustsIII. An Iron Nail Rusts• When iron rusts, it must react and incorporate

oxygen to become a new compound.

III. Sample ProblemIII. Sample Problem

• Identify the following as physical or chemical properties.a) Hydrogen gas is explosive.

b) Silver has a shiny appearance.

c) Dry ice sublimes (goes from solid directly to vapor).

d) Copper turns green when exposed to air.

III. Physical/Chemical ChangesIII. Physical/Chemical Changes

• Physical/chemical changes are closely related to definitions of physical/chemical properties.

• physical change: matter changes its appearance, but not its composition

• chemical change: matter changes its composition

• Chemical changes occur through chemical reactions in which reactants become products.

III. Physical/Chemical ChangesIII. Physical/Chemical Changes

III. Sample ProblemIII. Sample Problem

• Categorize the following as either a physical or chemical change.a) Copper metal forming a blue solution

when dropped in concentrated nitric acid.

b) A train flattening a penny.

c) A match igniting a firework.

d) Ice melting into liquid water.

IV. There is No New MatterIV. There is No New Matter

• In ordinary chemical reactions, matter is neither created nor destroyed.

• Known as Conservation of Mass.

V. EnergyV. Energy

• Physical and chemical changes are accompanied by energy changes.

• energy: the capacity to do work• work: results from a force acting on a distance

V. Two Types of EnergyV. Two Types of Energy

• potential energy (PE): energy due to the position or composition of the object

• kinetic energy (KE): energy due to motion of the object

• An object’s total energy is the sum of its PE and KE

V. Energy ConversionsV. Energy Conversions

• The Law of Conservation of Energy states that energy is neither created nor destroyed.

• Energy can change from one form to another or transferred from one object to another.

V. Specific Types of EnergyV. Specific Types of Energy• Electrical energy is the energy

associated with the flow of electrical charge.

• Thermal energy is the energy associated with motions of particles of matter.

• Chemical energy is a form of PE associated with positions of particles in a chemical system.

V. Energy Unit ConversionsV. Energy Unit Conversions

• There are three common units for energy.

V. Sample ProblemV. Sample Problem

• The complete combustion of a wooden match produces about 512 cal of heat. How many kilojoules are produced?

V. System and SurroundingsV. System and Surroundings

• When describing energy changes, we need reference points.

• system: object of study

• surroundings: everything else

• Systems with high PE tend to change such that their PE is lowered.

V. Energy DiagramsV. Energy Diagrams

• Chemical reactions can either be exothermic or endothermic.

• exothermic: release energy to surroundings

• endothermic: absorb energy from surroundings

V. Sample ProblemV. Sample Problem

• Identify the following changes as exothermic or endothermic.a) Water freezing into ice.

b) Propane burning.

c) Isopropyl alcohol evaporating from skin.

VI. Thermal EnergyVI. Thermal Energy

• Atoms and molecules of matter are in constant, random motion, which is the source of thermal energy.

• More motion = more thermal energy.

• Is there a way to easily measure this motion?

VI. Temperature and HeatVI. Temperature and Heat

• Temperature is the measure of the thermal energy of a substance.

• The hotter an object, the greater the motion of its particles, and the greater the thermal energy.

• Heat is the transfer or exchange of thermal energy caused by a temperature difference.

VI. Temperature ScalesVI. Temperature Scales

VI. Temperature ConversionsVI. Temperature Conversions

• The formulas below allow conversion between different temperature units.

VI. Sample ProblemVI. Sample Problem

• Convert 67 °F to kelvin and degrees Celsius.

VII. Heating a SubstanceVII. Heating a Substance

• When you heat a substance, its temperature changes.

• The amount of change depends on the substance.

• heat capacity: quantity of heat needed to raise the temp of substance by 1 °C

• specific heat capacity: quantity of heat needed to raise temp of 1 g of substance by 1 °C

VII. Specific Heat CapacitiesVII. Specific Heat Capacities

VII. Energy and Heat CapacityVII. Energy and Heat Capacity

• Heat absorbed and temperature change are directly related as shown in the equation below.

VII. Sample ProblemVII. Sample Problem

• Calculate the heat necessary to warm a 3.10 g sample of copper from -5.0 °C to 37.0 °C if the specific heat capacity of copper is 0.385 J/g °C.

VII. Sample ProblemVII. Sample Problem

• A sample of lead (C = 0.128 J/g °C) absorbs 11.3 J of heat, rising in temperature from 26 °C to 38 °C. Find the mass of the sample in grams.

VII. Sample ProblemVII. Sample Problem

• A 328-g sample of water absorbs 5.78 kJ of heat. If the water sample has an initial temperature of 35.3 °C, what will be its final temperature? Note that C = 4.18 J/g °C for water.