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Introduction to Chemistry – Background for Nanoscience and Nanotechnology Prof. Petr Vanysek
Introduction to measurements Introduction to measurements Distance/size dynamics of the scale – from the wavelength of x-rays to astronomic distances. focus on the “middle” scale size from visible objects – person, hand (where did inch come from?), fingernail thickness, hair diameter, mite, microbe, virus, finally atom and a molecule.
Wide range of dimensions Electromagnetic spectrum Relevant dimensions: kilometers (10+3 m) meters centimeters (2-1/2 = 1 inch) millimeter nanometers Angstroms (10-10 m) – size of an atom Atom: Electrons going around the nucleus
Units of Measurement SI Units • There are two types of units: • fundamental (or base) units; • derived units. • There are 7 base units in the SI system.
Units of Measurement Base SI Units
Units of Measurement SI Units Selected Prefixes used in SI System
Units of Measurement SI Units • Note the SI unit for length is the meter (m) whereas the SI unit for mass is the kilogram (kg). • 1 kg weighs 2.2046 lb. Temperature There are three temperature scales: • Kelvin Scale • Used in science. • Same temperature increment as Celsius scale. • Lowest temperature possible (absolute zero) is zero Kelvin. • Absolute zero: 0 K = -273.15 oC.
Measurements - Distance Standard units: length Meter (a little more than 3 feet) too large for some purpose millimeter, centimeter (multiples of 10, e.g., 1 meter = 1000 cm) Inch – nonstandard unit, thumb (sp. thumb=pulgar, inch=pulgada, greek inch=daktulos=finger)
Why dimensions matter? Nanomaterials – particles of nanometer size Nano-scale materials often have very different properties from bulk materials e.g. color and reactivity • 3nm iron particle has 50% of atoms on the surface • 10nm particle has 20% of atoms on the surface • 30nm particle has 5% of atoms on the surface
Squared and cubed distance Area = distance squared Volume = distance cubed the liter is a basic volume unit in chemistry, is is one decimeter cubed, of 10x10x10=1000 cm cubed. It is somewhat larrer than one quart
Units of Measurement Volume • The units for volume are given by (units of length)3. • SI unit for volume is 1 m3. • We usually use 1 mL = 1 cm3. • Other volume units: • 1 L = 1 dm3 = 1000 cm3 = 1000 mL
Concentration Amount per volume grams per liter moles per liter
Amount of material mass – in kilograms or in grams count of particles 12 = dozen 500 = ream 6.022 x 1023 = mole
Temperature Vigor of movement of paticles – atoms or molecules. Scientific units – Degrees Celsius (water freezes at zero and boils at hundred. Kelvin – same spacing as Celsius, starts at absolute zero and 0 oC is 273.15 K.
Change of volume with temperature Thermal expansion – volumetric thermal expansion.
Conversion of temperature units Some units need to be converted, e.g., centimeters to inches, which is simple multiplication. Lcm = 2.54*Lin Temperature conversiton Fahrenheit to Celsius is a bit more involved Tc = (5/9)*(Tf-32) Tf = ((9/5)*Tc)+32
Why Study Chemistry? Chemistry is the study of the properties of materials and the changes that materials undergo. Chemistry is central to our understanding of other sciences. It is substantial part of nanoscience and nanotechnology .
The Study of Chemistry The Molecular Perspective of Chemistry Matter is the physical material of the universe. Matter is made up of relatively few elements. On the microscopic level, matter consists of atoms and molecules. Atoms combine to form molecules. As we see, molecules may consist of the same type of atoms or different types of atoms.
Classification of Matter States of Matter Matter can be a gas, a liquid, or a solid. These are the three states of matter. Gases take the shape and volume of their container. Gases can be compressed to form liquids. Liquids take the shape of their container, but they do have their own volume. Solids are rigid and have a definite shape and volume.
Classification of Matter Pure Substances and Mixtures Elements consist of a unique type of atom. Molecules can consist of more than one type of element. Molecules that have only one type of atom (an element). Molecules that have more than one type of atom (a compound). If more than one atom, element, or compound are found together, then the substance is a mixture.
Classification of Matter Pure Substances and Mixtures If matter is not uniform throughout, then it is a heterogeneous mixture. If matter is uniform throughout, it is homogeneous. If homogeneous matter can be separated by physical means, then the matter is a mixture. If homogeneous matter cannot be separated by physical means, then the matter is a pure substance. If a pure substance can be decomposed into something else, then the substance is a compound.
Classification of Matter Elements If a pure substance cannot be decomposed into something else, then the substance is an element. There are 114 elements known. Each element is given a unique chemical symbol (one or two letters). Elements are building blocks of matter. The earth’s crust consists of 5 main elements. The human body consists mostly of 3 main elements.
Classification of Matter • Elements
Classification of Matter Elements Chemical symbols with one letter have that letter capitalized (e.g., H, B, C, N, etc.) Chemical symbols with two letters have only the first letter capitalized (e.g., He, Be).
Classification of Matter Compounds If water is decomposed, then there will always be twice as much hydrogen gas formed as oxygen gas. Pure substances that cannot be decomposed are elements. Mixtures Heterogeneous mixtures are not uniform throughout. Homogeneous mixtures are uniform throughout. Homogeneous mixtures are called solutions.
Properties of Matter Physical vs. Chemical Properties Physical properties can be measure without changing the basic identity of the substance (e.g., color, density, odor, melting point) Chemical properties describe how substances react or change to form different substances (e.g., hydrogen burns in oxygen) Intensive physical properties do not depend on how much of the substance is present. Examples: density, temperature, and melting point. Extensive physical properties depend on the amount of substance present. Examples: mass, volume, pressure.
Properties of Matter Physical and Chemical Changes 2 H2 + O2 2 H2O
Properties of Matter Physical and Chemical Changes • When a substance undergoes a physical change, its physical appearance changes. • Ice melts: a solid is converted into a liquid. • Physical changes do not result in a change of composition. • When a substance changes its composition, it undergoes a chemical change: • When pure hydrogen and pure oxygen react completely, they form pure water. In the flask containing water, there is no oxygen or hydrogen left over.
Review of Chemistry • States of Matter • Atoms, Molecules and Ions • Subatomic particles • Periodic Table • Covalent and ionic bonding • Chemical reactions • Inter-molecular forces
Matter • Solution: A uniform mixture of two substances such that molecules are separate from each other and move around randomly. Usually these are liquids. Solutions are usually transparent. • Colloids: A mixture of much larger particles ranging from 20 nm to 100 μm. Milk and paint are colloids. • Grains: Some materials are made up of many small crystals called grains. A grain is an individual crystal of such a solid. Different grains may have the crystal lattice oriented in different directions.
Elements, Atoms and Molecules • Atoms: All matter is made up of tiny particles called atoms. • Molecules: Sometimes two or more atoms are found bound together to form molecules. • The atoms can be categorized into about 115 different types based on the charge of the nucleus. • Elements are made up of only one type of atom. • The element carbon takes the form of graphite, diamond and buckminsterfullerene as well as others. • It is only possible to change one type of atom into another through nuclear processes such as take place in a nuclear power plant, the sun, atomic bombs or particle accelerators. • The elements do not change in ordinary chemical reactions.