video 1.4 classifying matter. matter anything that takes up space (has a volume) and has mass!
TRANSCRIPT
Video 1.4
Classifying Matter
Matter
Anything that takes up space (has a volume) and has mass!
Substances
A substance has a uniform and definite composition.
Elements are the simplest form of matter which cannot be broken down chemically. They are listed by name on Table S.
Compounds are made up of two or more elements that are chemically combined in a fixed ratio.
Mixtures
A mixture is comprised of two or more substances.
Homogeneous: a uniform mixture also known as a solution. You can not see its parts. Sometimes gets the symbol (aq) for aqueous which means dissolved in water.
Heterogeneous: non uniform mixture. You can see the parts.
Mixtures
Mixtures have two parts: Solute: The substance(s) dissolving. Solvent: The substance that does the
dissolving.
What is the “universal solvent”?
Element, Compound or Mixture?
Homogeneous or Heterogeneous?
Rules of thumb:
If a single symbol, with one capitol letter is given or can be used to name the species, it is an element.
If two or more combined symbols, with two more more capitol letters are given or can be used to name a species, it is a compound.
All elements and compounds are homogeneous.If no chemical formula is given or can be found,
it doesn’t have a fixed ratio and must be a mixture. These species can be homogeneous or heterogeneous.
Separating Mixtures
There are many ways to separate a mixture. If it is heterogeneous, you many be able to just sort them with your hands. If not, you can use:
1.Decanting: The least accurate way to separate; you can pour off the top layer of liquid from the bottom layer. (You have probably done this at the beach with water and sand mixtures.)
2. Filtering: To separate a solid from a liquid, filter it using a funnel and filter paper. The solid stays on top, liquids pour through. (What happens if the solid is completely dissolved in the liquid?)
Separating Mixtures
Separating Mixtures
3. Distillation: When two or more liquids are mixed homogeneously, you can boil off each liquid separately using the following apparatus:
This is how
many water
bottling companie
s clean their
water.
Separating Mixtures
4. Chromatography: Mixtures can be dissolved and small samples can be placed on filter paper. The filter paper will be placed in a wet container, and the sample will rise to the top, separating each component out.
This method is usually used to determine of the sample is pure or not. It is not used to completely separate
the sample.
List observations for the solutions:
Video 1.5
Phases
Solids Liquids and Gases
Solids
Definite shapeDefinite volumeConstant
vibrationMolecules are
packed tightly in a geometric (crystalline) pattern
Liquids
No definite shapeDefinite volumeConstant motionNo arrangementMolecules are
closer together than a gas but further than a solid
Gases
No definite shape
No definite volume
No arrangement
Spread outCompressable
Pressure
Gases exert a pressure on surrounding substances because they are constantly moving and colliding with other surfaces.
Only in a vacuum, where there are no molecules, there is no pressure.
Gas pressure can be measured in atmospheres or kilopascals, according to reference table A.
1. Which represents a liquid? Solid? Gas?
2. Which has the highest melting point?3. Which has the weakest IMF?4. Which has the lowest boiling point?5. Which has the strongest IMF?6. Which has a definite shape?7. Which have a definite volume?
What is a vapor?
Vapors are the gaseous form of a substance that is normally a liquid or solid at room temperature.
Heat transfers from areas of high to low temperature
Endothermic reaction require you to put heat in.
Exothermic reactions require you to take heat out; heat exits.
Phase Changes
Identify the phase change and if it’s endothermic or exothermic:
EvaporationCondensationMelting FreezingSublimationDeposition
Liquid to gas endothermicGas to liquid exothermicSolid to liquid endothermicLiquid to solid exothermic
gas to solid exothermic
Solid to gas endothermic
Describe the following:
Melting point
Boiling Point
Freezing Point
MP and FP are the same Temperature for a pure substance since it uses the same phases!
Thermochemistry
The study of energy changes that occur in chemical reactions.
Kinetic Energy refers to energy of motion. (Temperature)
Potential Energy refers to stored energy.
Phase Change Diagrams
Where is the KE increasing? Where is the PE increasing? Where is KE stable? Where is the melting and boiling point?
1. Which line segment represents a liquid? A solid?
2. What is the boiling point?
3. What is the freezing point?
4. On what line segments is the PE increasing?
5. What is PE doing when it is not increasing?
6. Describe KE and PE.7. Where is the solid/liquid
equilibrium?8. What would happen if it was
heated further?
B C
ED
A
Cooling Curve
Identify the lines for solid, liquid and gas.Where is the KE decreasing? Where is the PE decreasing? Where is PE stable? Where is the melting and boiling point?
B
E
D
C
A
F
Video 1.6
Changes in the Lab
Changes in the Lab
Physical Changes require that the chemical not change composition. (Breaking, grinding, etc.)
Chemical Changes require that the chemical changes into a new substance. (Burning, reacting, etc.)
Physical or Chemical Changes?
Observations
Observations are made many ways. They can be either:
Qualitative: appearance or behaviors: not measured Quantative: a mathematical description.
and either
Extensive: dependant on the amount of matter Intensive: dependant on type of matter
Qual or Quant and Intensive or Extensive?
Rough or smooth
Shiny or dull
Large or small Kinetic energy
Classroom Slides
Name Observations ElementCompound
Homogeneous Mixture
Heterogeneous Mixture
Why?
Copper
Copper Sulfate
Sand
Magic Sand
Magnesium
Magnesium Nitrate
Salt
Sugar
Soap
Oil and Water
Tap Water
Purified Water
Hand in when finished: A student heats an unknown pure
solid until it remains a gas and obtains the following data:
1.Draw and label a graph with time on the x axis and temperature on the y axis.
2.What is the freezing point?3.What is the boiling point?4.At what time do you first see a
sign of the liquid phase?5.At what time do you last see a
sign of the liquid phase?6.Explain what would happen if
the student continued heating for another 30s.
Time (s)
Temp (C)
0 0
30 10
60 20
90 20
120 20
150 30
180 40
210 50
240 50
270 50
300 50
330 50
360 60