Section 1 of Chemistry Notes Info.
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
Physical 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
Changes of Matter
Many changes of matter happen. Changes occur in two different ways:
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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.
Evolution of a gas- the production of a gas is often observed by bubbling or by a change in color
Formation of a Precipitate- when two clear solutions are mixed and become cloudy, a solid precipitate has formed
Release or Absorption of Energy- change in temperature of the giving off of light energy are signs of energy transfer
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
Matter- Anything that has mass and takes up space
The space an object occupies is its volume
Volume—a measure of the size of a body or region in three-dimensional space
The method used to determine volume depends on the nature of the matter being examined
Quantity of Matter is Mass
Mass- a measure of the amount of matter in an object. It is not affected by the gravitational force
Balances measure mass usually in grams
It is the same no matter where it is in the universe
Mass is NOT Weight
Weight- the force produced by gravity action on mass
Its value can change with the location of the object in the universe
Measured in Newtons
II. Units of Measurement
Mass & volume are properties that can be described in terms of numbers
Numbers alone aren’t enough because their meaning might be unclear
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
System Internationale d’Units
Seven base units
Base units can be modified by attaching prefixes
Derived Units
Many quantities you can measure need units other than the seven basic SI Units
These units are derived by multiplying or dividing the base units
Properties of Matter
Properties of substances may be classified as physical or chemical
Physical Properties
Characteristic of a substance that doesn’t involve a chemical change, such as density, color, or hardness
Chemical Properties
A property of matter that describes a substance’s ability to participate in chemical reactions
Examples: reactivity with oxygen, sensitivity to light, exposure to heat
Density
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.
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:
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Elements- are pure substances that contain only one kind of atom
Has its own unique set of physical and chemical properties
Has its own chemical symbol
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
Diatomic elements- two of the same atom bonded together chemically
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