Transcript Notes Unit 2-1

Warm Up
9-1-16
1. The smallest particle in the world is called the
___________
2. Draw a picture of the atom, from your memory
3. Why are atoms hard to see?
Agenda
Homework
Go over Test results
Notes Unit 2-1
Lab Density Engineering
Finish lab
Test Questions
• To determine the density of an irregularly
shaped object, a student immersed the object
in 21 milliliters of H2 O in a graduated
cylinder, causing the level of the H2O to riseto
27 milliliters. If the object had a mass of 24
grams, what was the density of the object?
• 4g/ml
Test Questions
• A physical change occurs when a
A. copper bowl tarnishes.
B. peach spoils.
C. bracelet turns your wrist green.
D. glue gun melts a glue stick.
• glue gun melts a glue stick.
Test Questions
In the diagram, which picture best represents
a compound?
Unit 2-1
Substances Are Made of Atoms
Atomic Theory
• States that atoms are building blocks of all
matter.
• Three laws that support the current atomic
theory
Atomic Theory
Current Model
Electron cloud instead of orbital
The atom model will change when new/better data come out
Scanning Tunneling Microscope
(Skip)
Atomic Theory
• Law of definite proportions - chemical
compound always contain the same elements in
the exact same proportions by mass.
Oxygen
Carbon
Hydrogen
C2H6O2
Atomic Theory
• Law of conservation of mass – mass cannot be
created or destroyed. Mass in reactants equal
the mass in products.
baking
soda
CO2 gas
vinegar
solution
Sodium
bicarbonate +
2 grams
acetic
acid
2 grams
-------->
carbon
dioxide
+
4 grams total
Sodium
acetate
and water
sodium
acetate
+
H 2O
Atomic Theory
• Law of multiple proportions - the masses of
one element which combine with a fixed mass
of the second element, are in a ratio of whole
numbers.
Chemical Name
Nitrogen monoxide
Nitrogen dioxide
Nitrous oxide
Water
Hydrogen peroxide
Formula
NO
NO2
N2O
H2O
H2O2
Ratio
1:1
1:2
2:1
2:1
1:1
Atomic Theory
• Elements combine in whole numbers
Dalton’s Atomic Theory
• 1808 – John Dalton combined the three laws
and revised the early Greek idea of atoms
• Part of his theory are
incorrect by today’s
standards because of
our technology
Dalton’s Atomic Theory
1. Matter is made of atoms, which cannot be
subdivided into smaller components
2. Atoms of a element are identical in their
physical and chemical properties
3. Atoms of different elements differ in their
physical and chemical properties
4. Atoms combine in simple, whole-number
ratios to form compounds
5. Atoms are rearrange in a reaction but not
created, destroyed or changed (transformed)
Engineering Challenge
• Density and Archimedes’ Principle
-Create a boat to hold as much pennies as
possible without sinking
-Due next class
• Summary: Why and how does the atomic
model change over the years?