Some Notes & Terms to remember about Chemistry

Section 1 of Chemistry Notes Info.

1. Working with the Properties & Changes of Matter
   • Chemical- any substance that has defined composition
   • Everything you see is made up of chemicals
   • Even things you cannot see are made up of chemicals
   • Some exist naturally
   • Some are manufactured
   • Chemical Reaction- the process by which one or more substances change to produce one or more different substances

2. Physical States of Matter
   • Type and arrangement of particles in a sample of matter determine the properties of the matter
   • Most matter is one of the three states of matter

A. Properties of the Physical State

Solids- fixed volume and shape

Rigid structure

Liquids- fixed volume and variable shape

Takes shape of container

Gases- neither fixed volume or shape

Particles move independently

Will fill any container they occupy

3. Changes of Matter

Many changes of matter happen. Changes occur in two different ways:

1.  
   • Physical Changes
   • Chemical Changes

A. Physical Change

Changes in which the identity of a substance doesn’t change

-Changes state

-Dissolving

-Crushing

B. Chemical Changes

Identifies of substances change and new substances form.

Mercury (II) oxide  mercury + oxygen

Reactants Products

-Substance or molecule that -Substance that forms in a chemical

participates in a chemical reaction reaction

Atoms are not destroyed or created, so mass does not change during a chemical reaction.

C. Evidence of Chemical Change

Generally, evidence that a chemical change may be happening falls into one of four categories; you may observe more than one.

1. Evolution of a gas- the production of a gas is often observed by bubbling or by a change in color
2. Formation of a Precipitate- when two clear solutions are mixed and become cloudy, a solid precipitate has formed
3. Release or Absorption of Energy- change in temperature of the giving off of light energy are signs of energy transfer
4. Color Change in the Reaction System- look for a different color when two chemicals react

Section 2 of Chemistry Notes Info.

I. Density

Matter has Mass & Volume

1. Matter- Anything that has mass and takes up space
2. The space an object occupies is its volume
   1. Volume—a measure of the size of a body or region in three-dimensional space
   2. The method used to determine volume depends on the nature of the matter being examined
3. Quantity of Matter is Mass
   1. Mass- a measure of the amount of matter in an object. It is not affected by the gravitational force
   2. Balances measure mass usually in grams
   3. It is the same no matter where it is in the universe
4. Mass is NOT Weight
   1. Weight- the force produced by gravity action on mass
   2. Its value can change with the location of the object in the universe
   3. Measured in Newtons

II. Units of Measurement

1. Mass & volume are properties that can be described in terms of numbers
   1. Numbers alone aren’t enough because their meaning might be unclear
   2. Units of measurement are needed with the numbers

Quantity- something that has magnitude, size, or amount

Unit- a quantity adopted as a standard of measurement

2. System Internationale d’Units
   1. Seven base units
   2. Base units can be modified by attaching prefixes
3. Derived Units
   1. Many quantities you can measure need units other than the seven basic SI Units
   2. These units are derived by multiplying or dividing the base units

4. Properties of Matter

Properties of substances may be classified as physical or chemical

Physical Properties

1. Characteristic of a substance that doesn’t involve a chemical change, such as density, color, or hardness
2. Chemical Properties
   1. A property of matter that describes a substance’s ability to participate in chemical reactions
   2. Examples: reactivity with oxygen, sensitivity to light, exposure to heat
3. Density
   1. Density- the ratio of mass to volume of a substance. Often expressed in grams/cm3 for solids and liquids and g/L for gases

Density= mass/volume or D=m/v

Section 3 of Chemistry Notes Info.

1. Classifying Matter

-From the last section:

-Matter-anything that has mass and takes up space

-All matter is composed of Atoms

-Atom- the smallest unit of an element that maintains the properties of that element

Because matter exists in so many different forms, having a way to classify it is important for study.

It helps you to predict what characteristics a sample will have based on what you know about others like it.

Pure Substances- a sample of matter, either a single element or a single compound that has definite chemical and physical properties

Element- a substance that cannot be separated or broken down into simpler substances by chemical means; all atoms of an element have the same atomic number

There are two types of pure substances:

1.  
   1.  
      • Elements
      • Compounds

1. Elements- are pure substances that contain only one kind of atom
   1. Has its own unique set of physical and chemical properties
   2. Has its own chemical symbol
   3. Molecule- the smallest of a unit of substance that keeps all of the physical and chemical properties that of the substance; it can consist of one atom or two or more atoms bonded together
   4. Diatomic elements- two of the same atom bonded together chemically

2. Pure Substances

-Some elements have more than one form

-Allotrope- one of a number of different molecular forms of an element

-Compounds are Pure Substances

Compound- a substance made up of atoms of two or more different elements joined by chemical bonds