Look around you. You can see a variety of objects—books, desks,
chairs, and perhaps trees or buildings outside. All those things are made up of matter, but exactly what is matter?
Explaining what matter is involves finding properties that all matter
has in common. That may seem difficult, given that matter takes so
many different forms. For example, consider a rock. It takes up space. In other words, it has volume. Volume is the amount of three dimensional space that an object occupies. All matter has volume.
All matter also has a property called mass. Mass is a measure of the amount of matter. Mass is the measurement you make using a balance. Matter can thus be defined as anything that has mass and takes up space. These two properties are the general properties of all matter.
Matter comes in many forms. The fundamental building blocks of matter are atoms and molecules. These particles make up elements and compounds.
An atom is the smallest unit of an element that maintains the chemical identity of that element.
An element is a pure substance that cannot be broken down into simpler, stable substances and is made of one type of atom.
Example: Carbon is an element and contains one kind of atom.
(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:
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:
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.
Tea, Coffee – how can you separate the H2O from the solids?
Most sands (usually made up of a number of different types of grains)
Foods (pizza, salad, soup, etc)
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.
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.
Examples of colloids: (http://chemistry.about.com/od/solutionsmixtures/fl/Colloid-Examples.htm)
- insecticide spray
- whipped cream
- shaving cream
Sols (solid particles floating in a liquid)
- liquid detergent
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)
Comparison of properties
How to detect colloids
“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. “
How do we use math in chemistry?
Online textbook from American Chemical Society
Students are introduced to the idea that matter is composed of atoms and molecules that are attracted to each other and in constant motion. Students explore the attractions and motion of atoms and molecules as they experiment with and observe the heating and cooling of a solid, liquid, and gas.
- Molecules Matter
- Molecules in Motion
- The Ups and Downs of Thermometers
- Moving Molecules in a Solid
- Air, It’s Really There
Students help design experiments to test whether the temperature of water affects the rate of evaporation and whether the temperature of water vapor affects the rate of condensation. Students also look in more detail at the water molecule to help explain the state changes of water.
- Heat, Temperature, and Conduction
- Changing State—Evaporation
- Changing State—Condensation
- Changing State—Freezing
- Changing State—Melting