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Chemistry Overview
• Chemistry = The study of matter and how it changes
• Matter = anything that has mass and occupies space
Matter Not Matter
Categorizing Matter
Stuff
Matter Energy
Mixture Pure substance
Heterogeneous mixture
Homogeneous mixture
compound Element
2-1 What is Matter?
Matter
- made of atoms – the smallest particles that have the properties of an element.
-The properties and characteristics of matter all depend upon what atoms the matter is made of.
Classifying MatterPure Substances – has a constant
composition
1. Elements – made of only one type of atom
- cannot be separated by ordinary chemical or physical means
- ex: iron (Fe), copper (Cu), aluminum (Al)
Note: A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements. All compounds are molecules but not all molecules are compounds. Oxygen gas (O2) is a molecule, but not a compound.
Chemical Formulas
- C16H10N2O2 is the formula for a molecule of indigo, a dye
- It has 16 carbon atoms, 10 hydrogen atoms, 2 nitrogen atoms, and 2 oxygen atoms
- If a number appears before the formula, 6 C6H12O6 it means there are 6 molecules of glucose
Mixtures – blend of pure substances
- 2 or more combined substances in no definite amounts
- each substance keeps its original properties
Liquid Mixtures
Miscible – gasoline is made of more than 100 compounds dissolved
Immiscible – oil and water do not mix together well
Note: gases can mix with liquids – carbonated drinks - homogeneous
States of Matter
There are three basic components or parts to each state of matter that can vary:
1. Temperature
2. Closeness of particles
3. Energy of particles (E)
These components are closely related. Think about how the kinetic theory explains the relationships.
“Most matter found naturally on Earth is either a solid, a liquid, or a gas, but matter also exists in other states” (p46).
Plasma
– free electrons and ions of element; electrically charged gas
Temperature – higher than gases
Particle closeness – far apart; little or no order
Energy – High energy
Examples – fluorescent light bulb, neon signs, stars, lightning, plasma TV screens
Gases
Temperature
• Above the boiling point of the substance
• Steam burns are worse than water burns because boiling water = 100°C where steam can be 125°C
Particle Closeness
• With available space, gas particles spread apart as more Energy is added
• Distance between particles allows for a lot of movement
Other
• Gases take the shape of their containers.
• Gases exert pressure on closed containers
• Molecules of gas moving fast in balloon constantly hitting each other and sides of balloon.
Particle Closeness
• Particles are close together, but not as attracted to each other as in solid form
• Particles can move independently of each other
Energy Level
• Energy is absorbed or released to form solid or gas
Other• Liquids vary in rate at which they spread• This property is called viscosity• If liquid molecules have a strong attraction to
each other slower spread like molasses• Both liquids and gases can spread, so are called
fluids• Some substances do not have a liquid form at
normal temperature and pressure
Particle Closeness
• Particles are close allowing almost no movement… particles can vibrate in place
• Organized arrangement because molecules bond
• Solids maintain their own shape
Energy’s Role in Phase Changes
Energy is the ability to change or move matter
• Examples: electricity, batteries (stored), candles, food, etc
• Energy must be added to cause melting or evaporating. The molecules gain E and then move faster. Think of the kinetic theory.
• Energy is transferred from substance to surroundings when condensing and freezing.
Sublimation – change from solid directly to gas
• Dry ice = CO2 solid to smoky gas
• Ice in freezer will sublime and ice gets smaller
Law of Conservation of Mass
Mass cannot be created or destroyed.
• Mass before change = Mass after change
4. Chemical reaction
• XXX + YYY ZZZ
• Reactants Products
• 3 atoms + 10 atoms 13 atoms
• The amount of atoms entering into a reaction will be the amount that come out of the reaction.
Law of Conservation of Energy
Energy cannot be created or destroyed.
• Energy before change = Energy after change
• Energy is stored in many ways = food, gasoline, batteries