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Let’s review what we know already!. atom. An atom is the smallest particle of an element that has the chemical properties of the element All atoms of a particular element are the same. Chemical symbols. Scientists use chemical symbols to represent the elements - PowerPoint PPT Presentation
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Let’s review what
we know already!
atom An atom is the smallest particle of an
element that has the chemical properties of the element
All atoms of a particular element are the same
Chemical symbols Scientists use chemical symbols to
represent the elements They are one or two letter that stand for
the name of an elementExample:H is for hydrogenCa is for CalciumO is for oxygen
Periodic table Russian chemist, Mendeleev published
the table as a way to organize the elements
Ordered by their weights of their atoms and their properties
The elements in column are similar in property
Using the periodic table of elements
In order by atom weight Columns are their group (metals,
nonmetals, semimetals, and noble gases)
Each column has similar properties
Helium 2
He4. 003
Element name
Atomic number
Atom mass
When is a metal not an element?
When it is an Alloy! An alloy is a solution of two or more metals with its own properties.
Example:Steel (iron, carbon, chromium, nickel)Bronze ( copper, tin and sometimes zinc)
Why Alloy?Alloys are useful because their properties
are different from those of the metals from which they are made.
Some common uses:Hardware, plumbing, dentistry, tableware,
artwork, building materials
Is an Alloy a mixture or solution?
An alloy is both, a mixture and a solution!
• Mixture because the elements mixed together can be different amount (kind of like the fruit salad)
• Solution because the metal elements are evenly mixed throughout
Classifying Matter
How can matter be classified?
VocabularyPhysical propertiesChemical propertiesSubstanceMixtureElementCompoundAtomChemical symbol
Look around the classroom at different objects?
What materials do you think make up these objects?
Matter
All of the materials you mentioned are made of matter. They are all different kinds of matter.
Matter can be identified by its properties, or characteristics.
Physical properties Are characteristics that can be measured
or detected by the senses.
Examples:ColorSizeOdordensity
Chemical properties Describe how matter changes when it
reacts with other matter
Example: the fact that paper burns is a chemical property of paper
All matter can be divided into two major groups-Substances and Mixtures
Elements and Compounds
Other important words to know
Substance- is a material that always has the same makeup and properties, wherever it may be found
Mixture- is a combination of two or more substances.
Elements An element is a substance that cannot be
broken down by simple means into any other substance
There are 118 elements (90 found in nature, 22 not found in nature)
Examples:Aluminum Copper
compounds Is made up of two or more elements that
are chemically combined
Examples:WaterSugar
Compounds- how are they formed?
When elements combine to form compounds they are linked with chemical bonds
Water molecule
Atom of Oxygen and two atoms of Hydrogen boned together
Salt molecule
Sodium and chloride bonded together
Na is a soft metal that reacts explosively with water
Chlorine is a poisonous gas
When atoms combine to form molecules they loose their property and together with what they bind with create new properties for at molecule
This explains why we can eat table salt!
Chemical formula Chemical formula is a group of symbols
that show the elements in a compound. The numbers tell us how many of that
element.
Example: water, H2 O Two hydrogen and one oxygen
Living vs nonliving things We know that all things are made of
matter We also know that all things have atoms
and elements, either mixed together or pure
* **ALL Living things have Carbon ! ****This is also called organic material!
Organic compounds- “living things”
Example:Cholesterol which is found in cells of living
things. C 27 H 45 OH
How many atoms are in this molecule of Cholesterol?
Lesson review: Elements and compounds are both
substances, they cannot be broken down into other substances.
Elements contain only one kind of atom. Compounds are made up of two or more
elements that are chemically combined.
Review cont… Two hydrogen atoms and one oxygen
atom have combined to form a single molecule of a compound of water.
Use a periodic table to locate certain elements ( try: Iodine, chlorine, oxygen)
Lesson Part 2
Mixtures vs. compounds
Mixtures and compounds Both are made up of more than one
element
But, they are different…
Mixtures Elements keep their original propertiesExample: Iron shavings and sand mixture – iron is
magnetic so we could use a magnetic to separate the sand
Mixtures cont… Different composition- which means
different amounts of each element every time. They may be different depending on location and time.
Example: Fruit salad- all recipes(formulas) are different. Some fruit salad had 2
apples, 3 oranges, 1 banana, 12 strawberries. Another one may have 1 apple, 2 oranges, 5 bananas and 2 strawberries. But they
are both called fruit salad.
Some common mixtures Window glass Most building material- bricks, cement,
asphalt Air Human body contains many mixtures-
blood, sweat, tears, saliva
Separating mixtures Using the physical properties like size, appearance,
texture, color, odor, melting point, boiling point, density, solubility, and magnetic attraction
Example: Marbles and sand
compounds Always have the same composition They are chemically bonded, so the
original elements loose their properties and new properties are created
Example:Water because it has two hydrogen and
one oxygen and that will never be different.( same composition)
Review Lesson part 2
Q: Explain why a mixture cannot be represented by a chemical formula?
A: A mixture does not have a constant
makeup. It cannot be represented by a chemical formula because the proportions of the components can vary.
Review cont…
Q: What is the difference between a mixture and a substance?
A: A substance has a constant makeup and a set of constant properties; a mixture does not.
Review cont..
Q: Suppose you has a mixture of iron pellets, pebbles, and small wood pieces of all about the same size.
A: Magnet to attract the iron, add water to the other two and the wood will float and the pebbles will sink.
Investigation 3What is a solution?
Vocabulary:SOLUTIONSOLVENTSOLUTESURFACE TENSIONCOHESION
Remember mixtures?
The main non-living parts of our planet are mixtures
Air, Rocks, Water
Facts about mixing:even mixing vs. uneven mixing
Uneven-If we mixed sand, salt and water together
we would have an uneven mixture This means that no matter how hard we tried we could
not take two samples of the mixture and it would have an even amount of salt, sand and water in each.
One sample might have more sand and the other more salt … it is impossible to get them even
What happens if a mixture is spread evenly?
They are called solutions.
Solution-
A solution has two main parts ( solvent, and solute)
Solvent is the material that is present in the greater amount
Solute is the material present that is the smaller amount
Most common solutionsSugar dissolved in water.
Rate of solution-Which would dissolve faster, a cube of
sugar or loose sugar grains?
Stuff only can dissolve if the liquid touches the surface of the sugar.
So the loose sugar would dissolve faster because all of the grains would have the surface touched.
The sugar cube would have to dissolve a little at a time as the liquid dissolved the surface bit by bit.
What else can effect the rate of solution?
Increased temperature (heat it up)- Causes the particles to move faster and have more energy
Increasing the movement of the particles (stir it up)
-causes the particles to mix together quicker because it bounces the particles around
Suspension- Sometimes a mixture can mix for just a
limited amount of time
A suspension is a liquid mixture in which some particles are temporarily suspended in the mixture
Suspension example:Salad dressing
Suspensions ProjectAt home use household products to create
a suspension bottle with as many layers as you can. Write down how much of each material you used.
Remember –• density is a factor• Insolubility is another factor
?
Lesson part 3 review
Q : Explain why salad dressing is not a solution?A: particles of oil are unevenly distributed in the
mixture. The oil and vinegar will separate with time
Q: What do compounds and mixtures have in common?
A: Compounds and mixtures are both made with two or more substances
Lesson part 3 review continue…
Q: why is an alloy both a mixture and a solution?
A: It is a mixture because the components can be present in different amounts. It is a solution because the metal components are evenly mixed.
Lesson part 1 summary:
An element is made up of only one kind of matter; a compound is made up of two or more kinds of matter that are chemically combined and can be represented by a chemical formula.
Lesson part 2 summary:
Mixtures are made up of two or more kinds of matter that are physically combined; most mixtures can be separated into their components, using physical means.
Lesson part 3 summary:
Solutions are mixtures in which the parts are evenly distributed at the particle level; an alloy is a solution of two or more metals.
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