let’s review what we know already!

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.