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Classification of matter

Chapter 15: Classification of matter, Section 1: Composition of matter

Physical Science textbook

Section 1: Composition of Matter

 

I. Building blocks – if you closely enough, everything is made of atoms and molecules!

(here we see water molecules, made of H, H and O)

Atom: The smallest, stable building blocks of matter in the universe. Wicked tiny. A single sheet of aluminum foil is 50,000 atoms thick!

   Ex: Hydrogen, Carbon, Oxygen, Iron

Molecule: A group of two or more atoms bonded together

     Some molecules are all made of the same atom:

          O2, O3, N2, H2

     Some molecules (“Compounds“) are made of 2 or more different types of atoms

          water H2O, sugar  C6H12O6

So: Not all molecules are compounds. Some molecules (like H2) consist only of one type of atom.

Let’s look at this graphically:

atom molecule compound mixture

II. All atoms are “matter” – matter is anything that has mass and takes up space.

Matter can be found all over the Universe. We find it in many forms on Earth. The most common states of matter are:

III. Pure Substances vs. Mixtures

A pure substance is just something with a “fixed” composition. That means as you look through it, all parts appear exactly the same. Examples include:

Air

Water

Iron (a very common metal, made of only one kind of atom)

Steel (a very common metal alloy, made mostly of iron, but also some carbon, and a tiny percent of other metals such as manganese, chromium, nickel)

Copper (metal made of only one kind of atom)

Brass (metal alloy made of copper and zinc)

Mixtures are 2 or more things mixed together

* not chemically combined, easy to separate by physical means.

Examples:

Tea, Coffee – how can you separate the H2O from the solids?

Most sands (usually made up of a number of different types of grains)

Dirt

Foods (pizza, salad, soup, etc)

Granite, Concrete,

2 types of mixtures:

Homogenous mixture all the substances are evenly distributed throughout the mixture (salt water, air, blood, Coca Cola)

Heterogeneous mixture the substances are not evenly distributed (chocolate chip cookies, pizza, rocks)

 

______________________________________________

Solutions: Mixtures in a liquid

Solution –  2 substances evenly mixed together.

Solute – the substance to be dissolved (ex: sugar)

Solvent – the substance doing the dissolving (ex: water).

There is usually more solvent than solute.

Amount of solute that can be dissolved by the solvent = solubility.

solution solvent

Technically, even a solid can be a solution:

Consider the metal brass – it is a solid solution made of copper & zinc

 

____________________________________

Colloids – A solution with bigger particles.

  • They scatter light, so they are often foggy or milky when you look at them.

Source: http://www.chem4kids.com/files/matter_solution.html

Argon gas in H2O solution

Argon gas dissolved in water solution

Examples of colloids: (http://chemistry.about.com/od/solutionsmixtures/fl/Colloid-Examples.htm)

Aerosols

  • fog
  • insecticide spray
  • clouds
  • smoke
  • dust

Foams

  • whipped cream
  • shaving cream

Solid Foams

  • marshmallows
  • Styrofoam

Emulsions

  • milk
  • mayonnaise
  • lotion

Gels

  • gelatin
  • butter
  • jelly

Sols (solid particles floating in a liquid)

  • ink
  • rubber
  • liquid detergent
  • shampoo

Also see: What is a solution? Visualization and Problem Solving for General Chemistry

Suspensions – a heterogeneous mixture containing a liquid

  • the solid particles will settle (fall to the bottom)

____________________________

This flowchart shows us pure substances (left) vs mixtures (right)

Pure substance vs Mixture

Solutions/Colloids/Suspensions?

Comparison of properties

How to detect colloids

Tyndall effect

“Tyndall effect is seen here using a laser pointer. The glass on the left contains 5 ppm of HVAC colloidal silver and the one on the right is from the tap after the bubbles have settled out. “

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How do we use math in chemistry?

 


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