1. Atoms, Mixtures, Elements and Compounds
A Matter of Fact
Atoms, Mixtures, Elements and Compounds

2. Matter Anything that has mass and takes up space (volume) Examples:
A brick has mass and takes up space
A desk has mass and takes up space
A pencil has mass and takes up space
Air has mass and takes up space
All of the above examples are considered matter because they have mass and take up space. Can you think of anything that would not be considered matter?

3. Atoms
Smallest possible unit into which matter can be divided, while still maintaining its properties.
Made up of:
protons
neutrons
electrons
The solar system is commonly used as an analogy to describe the structure of an atom - +
For example, what is the
smallest possible unit
into which a long essay can be
divided and still have some meaning? - + + - + + - -

4. Atoms are so small that…
it would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen.
if you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter – about the size of a ping-pong ball
a human hair is about 1 million carbon atoms wide.
a typical human cell contains roughly 1 trillion atoms.
a speck of dust might contain 3x1012 (3 trillion) atoms.
it would take you around 500 years to count the number of atoms in a grain of salt.
C-C-C-C-C-… + 999,995 more
1 trillion atoms  .
Is made of approximately 3 trillion atoms
Just one of these grains

5. + Protons (+) Positively charged particles
Help make up the nucleus of the atom
Help identify the atom (could be considered an atom’s DNA)
Equal to the atomic number of the atom
Contribute to the atomic mass
Equal to the number of electrons + - +

6. Neutrons Neutral particles; have no electric charge+ -
Neutral particles; have no electric charge
Help make up the nucleus of the atom
Contribute to the atomic mass

7. - Electrons (-) Negatively charged particles
Found outside the nucleus of the atom, in the electron orbits/levels; each orbit/level can hold a maximum number of electrons ( 1st = 2, 2nd = 8, 3rd = 8 or 18, etc…)
Move so rapidly around the nucleus that they create an electron cloud
Mass is insignificant when compared to protons and neutrons
Equal to the number of protons
Involved in the formation of chemical bonds + - -

8. + The Atom’s “Center” - - -
Protons and neutrons are grouped together to form the “center” or nucleus of an atom.
Notice that the electrons are not apart of the nucleus + - - -

9. Atomic Number and Atomic Mass
Atomic Number (noun): The number of protons in the nucleus of an atom. In electrically neutral (no charge) atoms, this number is also equal to the number of electrons orbiting around the atom’s nucleus. The atomic number determines its position in the Periodic Table.
Atomic Mass (noun): The mass of a given atom or molecule. Number of protons and neutrons added together.

10. Mixtures, elements, compounds
Scientists like to classify things.
One way that scientists classify matter is by its composition.
Ultimately, all matter can be classified as mixtures, elements and compounds.

11. Why isn’t it a good idea to classify matter by its phases?
Because one kind of substance can exist in more than one phase – such as H20. And matter changes phases rather easily.

12. Why isn’t matter classified according to its physical characteristics, such as color?
Scientists wouldn’t find it very useful to group gold, sunflowers, and the sun together.

13. Scientists ask themselves these questions?
Is the matter uniform throughout?
Can it be separated by physical means?
Can it be separated by chemical means?

14. By asking these questions scientists can classify matter into:
Mixtures – two or more substances that are not chemically combined with each other and can be separated by physical means. The substances in a mixture retain their individual properties.
Solutions – a special kind of mixture where one substance dissolves in another.
Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means.
Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means.

16. Is it uniform throughout?
If the answer is no, the matter is a heterogeneous mixture.
Considered the “least mixed.”
Does not appear to be the same throughout.
Particles are large enough to be seen and to be separated from the mixture.

17. Examples of heterogeneous mixtures
Sand and pebbles
Oil and water
Powdered iron and powdered sulfur

18. Granite is a heterogeneous mixture.

19. Mixtures
A mixture of lead atoms and chlorine atoms. They exist in no particular ratio and are not chemically combined with each other. They can be separated by physical means.
A mixture of PbCl2 and PbCl4 formula units. Again, they are in no particular ratio to each other and can be separated without chemical change.
جمعه، 22 ربیع الأوّل، 1440

21. Is it uniform throughout?
If the answer is yes, the matter is homogeneous (looks the same throughout).
That leads us to another question.

22. Can it be separated by physical means?
If the answer is yes, the matter is a homogeneous mixture or solution.

23. Homogeneous Mixtures A mixture that appears to be the same throughout.
It is “well mixed.”
The particles that make up the mixture are very small and not easily recognizable.

24. Examples of homogeneous mixtures
Milk, toothpaste, and mayonnaise are homogeneous
mixtures. They are also colloids.

25. Colloids
In a colloid the particles are mixed together but not dissolved.
The particles are relatively large and are kept permanently suspended.

26. Colloids A colloid will not separate upon standing.
The particles are constantly colliding, and this allows a colloid to scatter light – thus colloids often seem cloudy.

29. Solutions
A solution is a type of homogeneous mixture formed when one substance dissolves in another.
It is the best mixed of all mixtures.
A solution always has a substance that is dissolved and a substance that does the dissolving.
The substance that is dissolved is the solute and the substance that does the dissolving is the solvent.

30. Ocean water is a solution

31. The universal solvent: Water

32. Water as a solvent Many liquid solutions contain water as the solvent.
Ocean water is basically a water solution that contains many salts.
Body fluids are also water solutions.

33. Metals dissolved in metals are called alloys.
Types of solutions
Solute
Solvent
Example
Gas
Air (oxygen in nitrogen)
Liquid
Soda water (carbon dioxide in water)
Solid
Ocean water (salt in water)
Solid
Gold jewelry (copper in gold)
Metals dissolved in metals are called alloys.

34. Air is a solution of oxygen and other gases dissolved in nitrogen

36. Can it be separated by physical means?
If the answer is no, the matter is a pure substance.
An element
Or a compound

37. Elements Elements are the simplest pure substance.
An element can not be changed into a simpler substance by heating or any chemical process.
The smallest particle of an element that has the properties of that element is called an atom.
An atom is the basic building block of matter.
There are more than one hundred known elements in the universe listed on the periodic table of elements.
These elements combine in such a way to create millions of compounds.

38. Elements All elements are made of atoms.
Atoms of the same element are alike.
Atoms of different elements are different.

39. Elements
In 1813, a system of representing elements with symbols was introduced.
Each symbol consists of one or two letters.
Two letters are needed for a chemical symbol when the first letter of that element’s name has already been used.

40. Common Elements Aluminum Al Bromine Br Calcium Ca Carbon C Gold Au
Helium He
Hydrogen H
Nitrogen N

41. Elements
A sample of lead atoms (Pb). All atoms in the sample consist of lead, so the substance is homogeneous.
A sample of chlorine atoms (Cl). All atoms in the sample consist of chlorine, so the substance is homogeneous.
جمعه، 22 ربیع الأوّل، 1440

42. Compounds Compounds are also pure substances.
But compounds are made from more than one element.
Water is a compound.
Water can be broken down into simpler substances – hydrogen and oxygen.

43. Compounds
Lead has two charges listed, +2 and +4. This is a sample of lead (II) chloride (PbCl2). Two or more elements bonded in a whole-number ratio is a COMPOUND.
This compound is formed from the +4 version of lead. This is lead (IV) chloride (PbCl4). Notice how both samples of lead compounds have consistent composition throughout? Compounds are homogeneous!
جمعه، 22 ربیع الأوّل، 1440

44. DIFFERENCE BETWEEN COMPOUNDS & MIXTURES
S. No.
MIXTURE
COMPOUNDS 1 2 3 4
The substance are mixed together, no reaction take place.
Composition can be varied
Properties of the constituents present, remain same.
Can be separated by physical method such as filtration, distillation etc.
Substance chemically react to form a new compound.
Composition of new compound is always same.
The properties of new compound are very different from those of the element in it.
Cannot easily be separated into its elements.
جمعه، 22 ربیع الأوّل، 1440