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
- 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
- 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
- Compounds
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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
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