Chemical Interactions Cliff Notes
Chemistry is the scientific inquiry into the properties, composition and interactions of matter (stuff).
Matter is anything that has mass and takes up space.
Investigation 1 Substances
Goal: In investigation 1, students identify the two substances in a mystery mixture by observing the
characteristics of the reactions that occur when pairs of known substances are mixed.
Substance: a type of matter defined by a unique (one of a kind) particle. (e.g. water, salt, baking soda)
A substance is a form of matter. There are millions of different substances on Earth. Each substance
is different from every other substance.
This label is for one of the substance in the 9 substances investigated. The first one is a chemical
name, second is the common name, and third is the chemical formula.
Chemical Reaction: change that occurs when
2 or more substances combine and create new
substances.
Common signs of a chemical reaction include a color change, a temperature change, a new gas
(bubbling) produced, a new solids produced, light is produced, or a change in smell.
Resources: Fossweb multimedia Two substance reactions (username: msb1st, msb2nd, msb3rd
password: Bacon123)
Investigation 2 – Elements
Goal: In Investigation 2, students learn that elements are the basic substance from which all common
matter is made.
This is the Periodic Table of Elements. The periodic
table is a display of fundamental substances called
elements. There are over 100 elements, over 90
naturally occurring ones. They are ultimately the
basic substances from with all matter/other
substances/stuff are made of.
Element: a fundamental substance that cannot be
broken into simpler substances by chemical or
physical process.
Each element has a name and is represented by a one or two letter symbol. Hydrogen has the symbol
H. Calcium has the symbol Ca. Element symbols are used as a kind of shorthand when writing the
names of elements. The symbols need to be written exactly. Students need to be careful when using
symbols: CO is not cobalt (symbol Co) but two elements: carbon and oxygen. Additionally, some
symbols reflect ancient names, usually Latin. For instance gold’s symbol is Au for the Latin name
aurum.
In Investigation 2, part 2, students examine the lists of ingredients on consumer product labels to
discover the elements present. Students should realize that most of the ingredients are not simple
elements but substances composed of elements.
Resources: Fossweb multimedia Periodic Table. Reading Elements
Investigation 3 Particles
Goal: In Particles students investigate the macroscopic properties of gas and develop a
particulate model to explain the invisible interactions that account for the observable behaviors
of a gas.
In this investigation, students focus on the gas produced from combining citric acid,
sodium bicarbonate, and water. Students devise a procedure to capture the gas
produced and accurately measure the volume of gas produced.
Students hypothesize, based on the chemical formulas of the starting substances what
the gas could be. They settle on carbon dioxide (CO2) as the most likely gas.
C6H8O7
NaHCO3
H2O
Students discuss gas in general, especially the mixture of gases, air. Air is composed of the substances
nitrogen, oxygen, plus some miscellaneous gases. Students confirm that air has mass and takes up space.
(video). Therefore, air is matter.
Students investigate the behavior of gases using air. They put together a closed
syringe system to observe and record observations of airs behavior when a
push or pull force is added.
Air can be forced into a smaller space (volume). Air that is forced (pushed)
into a smaller space is compressed air.
Compressed: reduced in volume as a result of applied force (push)
When the force holding the air in a smaller space is removed, the air expands.
When matter expands, it occupies more space (volume).
Expansion: an increase in volume
A given mass of compressed air occupies less space than the same mass of air when it is expanded.
Particle: The smallest piece of a substance that is still that substance (e.g. water particle, air
particles)
Some basic info about gases & air…
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Air, like all matter, is composed of tiny particles too small to see.
The air particles are not touching on another. There is space between them.
Particles are in constant motion, they bounce off one another and the sides of the their containers
all the time.
Air is a mixture of gases that form Earth’s atmosphere. It is mostly nitrogen (N2), some oxygen
(O2) and a very small amount of carbon dioxide (CO2), a few argon (Ar), and water (H2O) particles.
Gas particles are really, really, really small. A cubic centimeter contains 27 quintillion particles
(that is the number 27 followed by 18 zeros (27, 000,000,000,000,000,000)
Particles of gas are fairly far apart. If the air particles in a room were the size of basketballs, they
would be about 2.3 meters apart (7.5 feet).
Gas particles move fast, averaging 300 m/x (670 mph).
Every particle crashes into another particle 10 billion times per
second.
There is nothing between gas particles…nada, zip, absolutely
nothing!!
Because there is so much space, air particles can be forced closer
together (compressed)
Why can’t you push the particles until they touch? Because the fastmoving particles push back on the syringe plunger with a force
when they hit it. As the particles of gas get pushed closer together,
they hit the plunger more frequently.
When you stop applying force to the syringe plunger, the air
particles inside the syringe push up on the plunger and it moves out
of the syringe barrel. It moves out until the force applied by the air
particles pushing the plunger up is equal to the force applied by the
air particles outside pushing the plunger down.
Resources: FOSSweb multimedia – gas in a syringe (see notes above); Reading Particles and Particles
in Motion; Practice vocabulary words with Investigation 1-3 Quizlet