the science of chemistry
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The Science of Chemistry. Chapter 1 Chemistry I 5.0. Alchemy. How do you picture a chemist?. What is chemistry?. Chemistry is the study of all things and the changes they can undergo. Chemistry is called a central science because it overlaps so many sciences. - PowerPoint PPT PresentationTRANSCRIPT
The Science of Chemistry
Chapter 1
Chemistry I 5.0
Alchemy
How do you picture a chemist?
What is chemistry?
l Chemistry is the study of all things and the changes they can undergo.
l Chemistry is called a central science because it overlaps so many sciences.
l Chemical – is any substance with a definite composition.
What is chemistry?
l Changes in chemicals (A.K.A.) chemical changes
l The process in which one or more substances change to produce one or more different substances.
l Matter – The stuff in which everything is made up of. Matter can be defined as anything with mass and volume.
States of Matter
State Shape Volume Movement Structure
Solid
Liquid
Gas
Definite Definite
DefiniteIndefinite
Indefinite Indefinite
Vibrate Slightly
Move More
Move the fastest
Most Rigid
Less Rigid
Least Rigid
States of Matter
States of Matter
melting
freez
ing
condensing
evaporating
depositionsublimation
Solid
Liquid Gas
Physical Changes
l Do NOT change the identity
l Often change what the substance looks like
l Examples: mixing ice tea in water, crushing a rock, freezing water
Chemical Changes
l Alter the identity of the substance.
l The new substance has a different composition than the beginning substances.
l Examples: rusting and burning
l A shorthand way to express a chemical reaction is with a chemical equation.
Chemical Equations
l The substances on the left side of the arrow are called the reactants. They are the starting materials in the reaction.
l The substances on the right side of the arrow are called the products. They are the ending materials in a reaction.
A + B C + D
Examples of Chemical Equations
2 2 2
2 2 2 2
2 2 3
2 2
3 2
H O H O
H O H O
N H NH
Signs of a Chemical Change
l Gas production – bubbles, odor, fizz, smoke
l Color change
l Release or absorption of energy – light or temperature change
l Formation of a precipitate – a solid substance that falls out of solution
Law of Conservation of Matter
l Matter is neither created nor destroyed, it just changes forms.
l Ex.: Where does matter go when you burn a piece of paper?
Describing Matter
l Volume – The amount of space an object takes up
l Measurement Device: ruler or graduated cylinder
Describing Matter
l Mass-The amount of matter in an objectl Measurement Device: Balance
Describing Matter
l Weight – a measure of the gravitational force exerted on an object
l Changes with your location in the universe
l Compare mass and weight of a person on earth and on the moon
Weight vs. Mass Demo
Types of Measurements
l Qualitative: Describes something using the 5 senses
l Quantitative: Uses numbers in the description
¡ Quantity – something that has magnitude, size, or amount.
¡ Unit – a quantity adopted as a standard of measurement
International System of Measurements
l Based upon multiples of 10l 7 metric units are base units.
Origin of the Metric System
l During the18th century scientists measured the distance from the earth’s equator to the North Pole and divided it into ten million parts.
l This number is equal to exactly 1 meter.
Metric Units
l Mass kilogram kg balance
l Length meter m ruler
l Timesecond s clock
l Temp. Kelvin K thermometer
The Meter
l The original standard for the meter was kept in a safe in France.
l The meter stick is a replica of that standard.
l A meter is made up of 100 centimeters and 1000 millimeters.
l Lasers are now used to determine the standard for a meter.
The Gram
l Mass is the amount of matter in an object.
l 1 cm3 of water = 1 gram.
l The standard kilogram is kept under lock and key in Washington, DC and other cities around the world.
Derived Units: Units that come from other unitsl Area meters squared m2
ruler l x w
l Volume meters cubed m3
ruler or graduated cylinder l x w x h
The Liter
l The liter is 1000 mLl 10cm x 10cm x 10cml 1 liter = 1000 cm3 = 1 dm3
l 1 milliliter = 1 cm3 = 1 cc = 20 drops
=
Metric (SI) Prefixesl Mega M 1,000,000l Kilo k 1,000l Hecto h 100l Deka da 10l BASE UNITl Deci d .1l Centi c .01l Milli m .001l Micro µ .000001l Nano n .000000001l Pico p .0000000000001
Properties of Matter
l Physical = A characteristic of a substance that does not involve a chemical change
l Examples: texture, state of matter, density, hardness, boiling point
l Density = The ratio of the mass of a substance to the volume of the substance.
l D = mass / volume
Density Column
Density
Which is more dense: Diet or Regular Soda?
Density of an Irregular solid:
1- Find the mass of the object2- Find the volume if the object by water
displacement!
Properties of Matter
l Chemical = A property of matter that describes a substance’s ability to participate in chemical reactions.
l Examples: reacting with oxygen, light sensitivity
Classification of Matter
Classification of Matter
l Pure substances: A sample of matter with a definite composition; means definite chemical and physical properties.
l Includes: Elements and Compounds
Elements
l Made up of one type of atom.
l An atom is defined as the smallest unit of an element that maintains the properties of that element.
l Cannot be separated into similar substances by chemical means.
l Represented by symbols.
Elements (cont.)
l Can exist as atoms or molecules. A molecule usually consists of two or more atoms.
l Ex. N2, O2, F2, Cl2, Br2, I2, H2
l Elements that have more than one form are called allotropes.
l Ex. Carbon (graphite and diamond)
Compounds
l Made up of 2 or more different elements combined in a fixed position.
l Can be separated through chemical means.
l Represented by formulas.
l Electrolysis allows chemists to distinguish between elements in compounds.
l Examples: CO2 and H2O
Elements Vs. Compounds
Mixtures: A combination of 2 or more substances that are not chem. combined.
l Heterogeneous Mixture: Composed of dissimilar components; Can see the parts
l Ex. Cookie, salad, asphalt
l Homogenous Mixture: Uniform structure or composition throughout
l Ex. Lemonade, steel, air
l Alloy: A solid homogeneous mixture (14 caret gold, steel, pewter)
Examples of Alloys
Brass is an alloy of copper and zinc.
Steel is an alloy of carbon and iron.
Bronze is an alloy of copper and tin.
Microscopic look at mixtures
Separating Heterogeneous Mixtures
l Filtration: Pour liquid through paper and collect residue (solid)
Separation of Homogeneous Mixtures
l Distillation: Separation based on a difference in boiling points
Another Look at Distillation
l Distillation Demol A Closer Look at Distillation
Separation of Homogeneous Mixtures
l Crystallization: Evaporate liquid and solid will recrystallize
Separation of Homogeneous Mixtures
l Chromatography: Separation of pigments of dye