02 matter, change and energyPresentation Transcript
CHEM-111 General Chemistry Unit-2 Matter, Change and Energy بسم الله الرحمن الرحيم by CHEMISTRY DEPARTMENT
CONTENTS 1. DEFINITION OF CHEMISTRY 2. THE SCIENTIFIC METHOD 3. TEMPERATURE 4. PHYSICAL STATE OF MATTER 5. MIXTURES 6. PHYSICAL PROPERTIES & PHYSICAL CHANGES 7. CHEMICAL REACTION & CHEMICAL PROPERTIES 8. ELEMENTS & COMPOUNDS 9. MASS CONVERSION 10. ENERGY INTERCONVERSION 11. EXOTHERMIC AND ENDOTHERMIC PROCESS Matter, Change, and Energy
Chemistry is the study of, mainly the composition, structure, reactions and properties of matter . Some main branches are- Biochemistry Study of biological chemicals Organic chemistry Carbon based compounds Inorganic chemistry All other elements Analytical chemistry Methods of analysis Physical chemistry Theory and concepts Branches of Chemistry
Anything that occupies space and has mass is called matter .
Specific kind of matter is called material.
Mass is the measurement of amount of matter present in an object.
All the chemicals that make up our world are example of matter,
whether they may be found in medicines, pencils, food or people.
Materials Specific kind of matter Steel, ocean water, glass, sand, blood Homogeneous Uniform distribution of particles Heterogeneous Non uniform distribution of particles Homogeneous mixtures Two materials present in uniform Composition throughout Heterogeneous mixture Two materials present in non uniform Composition throughout Substances Homogenous material with the Same composition, pure, Non mixtures Elements Composed of one kind of atoms Compounds Composed of more than one Kind of atoms Solutions Uniform distribution of two materials
What are elements? All matter are made up of elements ,which are primary substances, cannot be broken down by chemical means . There are now 115 different kinds of elements. Of these, 92 elements occur naturally and are found in different combinations. Hydrogen (H), carbon (C), nitrogen (N) and oxygen (O) are the elements that make up most living organisms . Some other elements found in living organisms are: Magnesium (Mg), calcium (Ca), phosphorus (P), sodium (Na), potassium (k) .
Elements and Compounds Iron (Fe) and Compounds Mercury (Hg) and compounds Two or more elements chemically combined to form new substance called a compound . Proteins, carbohydrates, lipids, water, salt, carbon dioxide and hemoglobin are few examples of compounds.
disorder short range order Solid States of Matter Gas Liquid long range order have vibration motion .
are in constant random motion .
free to move randomly Molecules Molecules Molecules
Characteristics of Matter States of Matter Fluidity or Rigidity Compres-sibility Volume Shape Inter-molecular space Inter-molecular forces Solids Rigid No Fixed Fixed Very Less Strong Liquids Fluid Very Low Fixed Not Fixed Slightly more Less strong or Weak Gases Fluid Very High Not Fixed Not Fixed More Extremely Weak
Change of State of Matter
H 2 O
Ice Vapor Water Water changes from solid to liquid & then gas by heating. It is a physical change which changes the arrangement of water molecules only, not the formula of water. solid gas liquid
The mixing or combination of two or more substances is known as a mixture .
There is no chemical bonding exists among the substances present in mixtures .
Air is a mixture of many gases.
Plasma, urine and blood are also few examples of mixtures.
Mixture of gases constituting the earth's atmosphere. Some gases occur in steady concentrations. The most important are molecular nitrogen (N 2), 78% by volume, and molecular oxygen (O 2), 21%. Small amounts of argon (Ar; 1.9%), neon (Ne), helium (He), methane (CH 4), krypton (Kr), hydrogen (H 2), nitrous oxide (N 2 O), and xenon (Xe) are also present in almost constant proportions. Other gases occur in variable concentrations: water vapour (H 2 O), ozone (O 3), carbon dioxide (CO2 2), sulfur dioxide (SO2 2), and nitrogen dioxide (NO2 2).
Two categories of mixtures are: 1- HOMOGENEOUS (Uniform composition) Example – Plasma, sugar solution etc. 2-HETEROGENEOUS ( Non-uniform composition) Example – Blood, Urine, Oil with water etc. Mixtures: Oil and water forms a heterogeneous mixtures before shaking after shaking Oil water
Difference between Compound and Mixture 1- The temperature of compound will stay constant as it melts but temperature, in mixture of a substance will change gradually. Example: Ice melts at 0 0 C. While mixture of ice with NaCl melts, at lower temperature than 0 0 C. 2- The identity & chemical properties of substances are changed in preparation of compound. While component of a mixture retain their chemical properties. Example: A mixture of Cu and S can be observed before and after chemical change.
Formation of compound is a chemical change , Mixture is formed by physical change coil of red –colored copper wire and yellow powdered sulfur. When mixed in the crucible, the copper and sulfur retain their individual properties When the mixture of copper and sulfur is heated a reaction takes place and a new substance called copper sulfide is formed., CuS compound
Physical Property Property which is observed without changing the chemical makeup of a substance. For example melting point of ice is 0 0 C and boiling point of water is 100 0 C which is always found same in normal conditions. Formula of water , water vapors and ice remains same,H 2 O, in all these physical sates.. Qualitative Property Quantitative Property color density odor melting point taste boiling point feel or touch compressibility
The change that does not change the chemical structure of a substance. e.g.
Change of ice to liquid, does not affect chemical formula of H 2 O .
A beaker and broken beaker -composition remains same, so physical change.
Melting of wax on heating and again solidification on cooling .
Sublimation of iodine is also a physical change
Sublimation of iodine Physical Change
The study of changes that occur when chemicals interact with each other to form entirely different substances.
The symbolic representation of a chemical substance in form of assembled symbols MOLECULAR REPRESENTATIONS H 2 O-water
Formula are used to represent :
How many are there of each element
How the elements are connected to each other.
The names of elements in a compound.
CH 3 CH 2 OH-ethyl alcohol 2 hydrogen 1 oxygen 2 carbon, 6 Hydrogen 1 oxygen Chemical Formula Examples
Chemical Change In, a chemical change the reacting substances change into new substances that have different formulas and different properties. For instance , when silver tarnishes, the bright silver metal becomes dull because it changes into Ag 2 S. Tarnishing of silver 2 Ag + S Ag 2 S silver sulphide Rusting of iron 4 Fe + 3 O 2 2Fe 2 O 3 iron oxygen iron oxide
Evidences of Chemical Change
New substances produced, old substances destroyed
Heat added or absorbed
Light added or absorbed
Precipitation (solid formed)
Explosion (fast gas)
Light Gas Explosion
Comparison of Some Chemical and Physical Changes Chemical Changes Physical Changes Rusting nail Melting ice Bleaching a stain Boiling water Burning wood cutting wood Tarnishing silver Tearing paper Fermenting grapes Breaking a glass Souring of milk Pouring milk
Energy and Heat Energy: is defined as the ability to do work . Classification of Energy 1-Potential energy (stored energy) 2-Kinetic energy (energy of motion) The food you eat has potential energy. When you digest, you convert its potential energy to kinetic energy to do work in the body.
Kinetic Theory of Matter Matter is composed of small particles; atoms, molecules. They are in constant & random motion. Particles due to continuous motion possess kinetic energy. K.E=1/2mv 2 K.E ( av ) T ( abs ). molecule s Magnified view of
Energy in Chemical Reactions
Heat Capacity of Matter Heat is the energy associated with the motion of particles in a substance
An energy change often shows that a chemical reaction is happening.
Sometimes heat energy is given out and the chemicals get hot .
These reactions are called Exothermic reactions.
In other reaction, heat energy is taken in and the chemicals get colder .
These are called Endothermic reactions.
Exothermic and Endothermic Reactions
Heat of Reaction:
Energy difference between reactants and the products
Energy of the product is lower than the reactant and heat is given out .
Energy of the product is higher than the reactant and heat must be absorbed for products to form.
Exothermic and Endothermic Reactions Examples
CH 4 + 2O 2 CO 2 + 2H 2 O + 213kcal
H 2 + I 2 + 12 kcal of heat 2HI
Reaction Energy Change Heat in the Equation
Exothermic Heat released Product side
Endothermic Heat absorbed Reactant side
Heat absorbed Methane Heat released
1. Which are homogeneous or heterogeneous mixtures?