ch1: general chemistry
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CH1: General Chemistry
The Heart of the Matter
Bring out ½ sheet of paper
Name the three states of matter (bonus of a half-point each if you can name the two others)
In outer space, would an apple have less mass?
Back on Earth, if we cut this apple into segments, what type of changes would occur? (physical or chemical?)
Problem Solving
I have a glass jar filled with a mixture of mineral oil and acetone, both of which are colorless. Oil and acetone do not mix, and thus form two layers in the jar.
Liquid A
Liquid B
Problem Solving
You want to know which of the liquids is acetone and which is mineral oil, but you can’t tell by the appearance alone. Thus, you conduct an experiment and find that:– 2.00 ml of acetone weighs 1.58 grams– 1.50 ml of mineral oil weighs 1.26 grams
What are the densities (in g/ml) of mineral oil and acetone? Based on this, which liquid floats on top?
The Heart of the Matter
MATTER – the stuff the universe is made of. It’s anything that has mass and occupies space
MASS – the amount of matter an object contains
Mass vs. Weight
Mass is constant for a given sample of matter
Weight depends on the strength of gravitational force
Will an apple have less mass in outer space?
NO
Classifications of matter
SOLID – definite volume,
definite shape
LIQUID – definite volume,
no permanent shape
GAS – no definite volume or shape
urea
chlorine
Titration setup
Atoms and molecules wiggle?
Matter moves on an atomic level – even solids.
– Solids are held in rigid structures;
their atoms vibrate– Liquid molecules slip and slide
against each other
– Motion and other forms of energy
Energy and state changes
Why does heating a substance result in state changes (e.g. ice to water to steam)?
Thermal to kinetic energy
Plasma: the fourth state of matter
So much energy, the electrons are ejected.
“ion soup”
Plasma
Examples of Plasma
Absolute Zero
-273 degrees C Outer space? Technology: less
than 1 millionth of a degree above absolute zero
Bose-Einstein condensates
BEC, briefly
Atoms occupy the same space
Atoms are indistinct from each other and form one blob
Test yourself
Steam Fluorescent light Gravel Milk Mercury (room temp)
Classifying by composition
Pure substances vs. Mixtures– Substances: fixed composition and distinct
properties (e.g. salt, water)– Mixtures: combos of 2 or more substances, each
retaining its own properties (e.g. sand, milk)
HETEROGENOUS
HOMOGENOUS
MIXTURES
COMBINATION OF TWO OR MORE SUBSTANCES IN WHICH EACH SUBSTANCE RETAINS ITS OWN CHEMICAL IDENTITY
– Homogenous– heterogenous
ALLOYS : Mixtures of metalseg. YELLOW BRASS (Cu, Zn)
STAINLESS STEEL (Fe, Cr, Ni, C) PLUMBER’S SOLDER (Pb, Sn) STERLING SILVER (Ag, Cu) GOLD ALLOYSAMALGAMS : Metal mixtures with mercuryCOLLOIDS: Intermediate dispersions or suspensions (Borderline)
COLLOIDS EVERYWHERE
ALL MATTER
Can it be separated by physical means?
PURE SUBSTANCE
HeterogeneousMixture
Homogeneous
Can it be decomposed into other substances by chemical processes?
Element Compound
Is it uniform throughout?
YES
YES
YESNO
NO
NO
Homogeneous Mixture (SOLUTION)
Classification “pachinko”
e.g. SAND
e.g. seawater
Pure Substances
ELEMENTS – cannot be decomposed into simpler substances.
Pure Substances
Elements – composed of only one type of atom Compound – composed of two or more different
types of atoms
Classification Recap
States: solid, liquid, gas, plasma, BEC Composition
– Mixtures: homogenous and heterogenous– Pure substances
Elements Compounds
Properties of Matter
PHYSICAL PROPERTIES- Measurable without changing the identity and composition of the substance
CHEMICAL PROPERTIES- Describe the way a substance may change or react to form other substances
INTENSIVE PROPERTIES-Do not depend on the amount of sample being examined.-Useful in identification Eg. Temp., Melting point, Density
EXTENSIVE PROPERTIES- Depend on the amount of sample being examined. Eg. Mass, Volume
Some Physical Properties
Temperature Color Boiling point Freezing point Hardness Density
Some chemical properties
Oxidation (rusting and tarnishing) Flammability Inertness
Changes in matter
Physical change – doesn’t entail any change in chemical composition
Chemical change – entails change in chemical structure
BOTH physical and chemical change
What type of change is this?
Next meeting
Read about atomic theory
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