Chapter #2 – Lecture Notes

SECTION #1 – WHAT IS MATTER

Everything in the world is made of matter.  Matter is anything that has volume (takes up space), and mass. On earth, matter exists in three states, solids, liquids, and gases.  There is a forth state of matter that exists in space called plasma.

Volume can be measured for all three states of matter.

1)          SOLIDS – The volume of a solid can be calculated by multiplying the length by the width by the height.

2)          LIQUIDS – The volume of a liquid can be found by pouring it into a graduated cylinder and reading the meniscus.  The meniscus is the curved surface of a liquid in a glass container.

3)          GASES – If you know the volume of the container, you know the volume of gas that’s in it because gases expand to fill their containers.

Mass can be found in all forms of matter.  Mass and weight are different things.  Mass is the amount of matter in an object.  Weight is a measure of the force of gravity on an objects mass.  Gravity is the force of attraction between objects due to their masses.  Objects with large masses have large a gravitational force.  Objects with small masses have a small gravitational force.  Gravitational force decreases as the distance between the objects increases.

Inertia – is the tendency of objects to resist any change in motion.  Due to inertia, objects at rest remain at rest until something causes it to move.  Mass is a measure of inertia, because objects with larger masses have greater inertia.

SECTION #2 – DESCRIBING MATTER

I) PHYSICAL PROPERTIES

A physical property of matter can be observed without changing the identity of the matter.  Physical properties can be used to identify matter.

EXAMPLES OF PHYSICAL PROPERTIES

1)      Color

2)      Odor

3)      Thermal Conductivity (ability to conduct heat)

4)      State (solid, liquid, gas)

5)      Malleability (ability to be hammered into thin sheets)

6)      Ductility (ability to be drawn into a thin wire)

7)      Density (amount of matter in a given space)
Density can be calculated using the formula D=M/V.
Density can be used to identify different substances.  This happens for 2 reasons, first, the density of a particular substance is always the same at a given temperature and pressure, and second, the density of one substance is different than the density of other substances.

 II) CHEMICAL PROPERTIES

 A chemical property describes a substance based on its ability to change into a new  substance with different properties.  Examples, flammability, reactivity with oxygen, reactivity with an acid, reactivity with water.  Reactivity means that when 2 substances get together, something happens.

  ***The characteristic properties of a substance are always the  same no matter what the size of the sample is.***

 TYPES OF CHANGES

1)      PHYSICAL CHANGES

A physical change is a change that affects one or more physical properties of a substance.  Physical changes do not change the identity of the substance.  Because of this, physical changes are easy to undo.

***DURING A PHYSICAL CHANGE, NOTHING NEW IS FORMED***

2)      CHEMICAL CHANGES

A chemical change occurs when one or more substances are changed into entirely new substances with different properties.  Whenever you have a chemical change you will also have a physical change.  Chemical changes and chemical properties are not the same thing.  A chemical property describes a substances ability to go through a chemical change.  A chemical change is the actual process by which the substance changes into another substance.  Because new substances are formed, you cannot reverse chemical changes using physical means, but some chemical changes can be reversed under the right conditions by using other chemical means.

WORKING WITH DATA

Before we can use the data we collect during an experiment, it must be organized. We do this using data tables and graphs.  When we make a data table, the first piece of information relates to the X value on a graph.  The second piece of information relates to the Y value. 

There are many different types of graphs, the most common one is the line graph.  A line graph is made up of 2 number lines that intersect at 0.  The horizontal line is the X-axis, the vertical line is the Y-axis.  When you set up the axis, the divisions should be equal and consistent.  You plot the points using the X and Y coordinates from your data table.  Data points will go on a line, not in a box.  When all points are plotted, connect the dots with a straight line from one point to the next until all points are connected.  You may or may not connect the first point to 0 depending on the instructions.