Developing Ideas about Matter Section A1.3. Objectives describe examples of practical applications...
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Transcript of Developing Ideas about Matter Section A1.3. Objectives describe examples of practical applications...
Objectivesdescribe examples of practical
applications of chemistry in food storage
identify and explain early forms of chemistry
outline the development of our understanding of the atomic model as consisting of protons, neutrons and electrons
give examples of chemistry based careers in the community
ReviewLast class:
◦Physical and chemical properties (what is the difference? Examples?)
◦What is the difference between a pure substance and a mixture?
◦What are signs of a chemical reaction? Which ones did we see in the demo?
Hand in: MSDS worksheet
Back in the day…People have been using chemical
properties of substances for centuries
First Nations people had extensive knowledge of plant use
Our ancestors began to understand relationship between temperature and states of matter
Food Chemistry
How do physical changes apply to food? Chemical changes? Examples?◦Physical changes: freezing (chemical
components stay the same)◦Chemical changes: baking (formation
of new substance)
Food Chem: Heating and FreezingHeating- temporary sterilization
◦Kills micro-organisms◦Canning- heat sterilization
Freezing- preserve almost indefinitely◦Prevents growth of micro-organisms
SaltingWay to preserve meat and fishMethod of dryingDraws water out of meat and
bacteriaUsed by sailors
FermentationBiochemical preservation
techniqueBacteria convert starches and
sugars into alcohol & carbon dioxide; others into acids◦Prevents growth of bacteria◦More digestible and higher vitamin
content◦Helpful in preventing scurvy
More Early ChemistryMetallurgy
◦Producing and using metals◦Early peoples used gold, copper,
silver, lead, and iron◦Used copper for weapons by
hammering it into shapes◦Annealing- heating copper so not
brittle when hammered
Metallurgy continued…Smelting- separating metal from
other elements in a compound ◦Way to get copper◦Done in Egypt by 4000 B.C.
Alloy- mixture of metals◦What is bronze an alloy of?◦Tin and copper◦Steel?◦Iron and carbon
Aristotle and MatterAristotle thought matter
composed of combinations of fire, earth, water, and air
Continuous (no such thing as a smaller piece)
Democritus- proposed tiny particles (atomos)
Didn’t test their ideas
AlchemyScience and magicExperiments to turn cheap
metals into goldMany important scientific
discoveries made◦Mercury, procedures for making
acids, developed lab equipment
Atomic TheoryTheory: a major idea that
explains a large amount of data; based on many experiments; may be changed when new data is collected
Atomic Theory: explains what the structure of the atom is like
Developing Theories about MatterFour classic models of atoms Examples of the scientific
processFounded on experimentsDalton, Thomson, Rutherford and
BohrModern model of the atom:
based on quantum mechanics
ThomsonDiscovered the electronExperimented with beams of
particles in a vacuum tubeFound that all elements produced
the same type of beam made of negative charges
Atoms made of smaller subatomic particles in different combinations
Electrons imbedded in positive sphere
RutherfordDiscovered the nucleusGold foil experiment
◦ Shot positively charged particles at a thin piece of gold foil
◦ Expected all particles to go right through, though some deflected and some reflected right back
◦ Unexpected result: like firing a cannon ball at tissue paper and having it bounce back!
◦ What does this mean?◦ http://www.youtube.com/watch?v=Q8RuO2ekN
Gw◦ http://www.youtube.com/watch?v=5pZj0u_XMb
c&safety_mode=true&persist_safety_mode=1&safe=active
Rutherford continued…What this means:
◦There is a strong, dense positively charged core
◦Called the nucleus◦Most of the atom empty space◦Nucleus very small (1/10 000 size of
atom)
BohrProposed that electrons
surrounded nucleus in specific energy levels
Found evidence based on light released by hydrogen atoms (gaps between energy levels)
Falling from higher to lower energy levels releases particular color of light
Bohr continued …Discovered every element has its
own unique pattern, and thus unique atomic structure
http://jersey.uoregon.edu/vlab/elements/Elements.html
Quantum Mechanical Model of the AtomElectron cloud around nucleusOccupy whole space all at once
at different energy levelsNucleus contains nucleons
◦Protons- positively charged◦Neutrons-no electrical charge
Atomic Models Activity: Summary Chart
Using your textbook, complete a chart with the following headings for the 5 models discussed
Atomic Models Activity: JigsawIn groups of 5, you will become
“experts” on a particular model of the atom
In your group, make a poster which explains the particular model you are given
Poster must teach concept in a way to answer the questions on the worksheet and be useful to your fellow classmates
You will teach your classmates about the topic so be comfortable with it!