SEPT 28 + 30, 2009 [JOANNE]

SEPTEMBER 28, 2009

Today we watched a video.
The class was to identify any chemical / physical changes shown in the video.
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PAGE 73: SECTION REVIEW 2-3
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LAW OF CONSERVATION OF MATTER:
- Matter can neither be created nor destroyed

A. CLASSIFICATION OF MATTER

• We can divide matter into two types:
• Homogeneous Substances
  
• Heterogeneous Substances

• HOMOGENEOUS: consists of only one visible component
  -distilled water, oxygen, graphite


• HETEROGENEOUS: contain more than one visible component
  -chocolate chip cookie, granite

B. PURE SUBSTANCES

there are two types of pure substances:
-Elements: substances cannot be broken down into simpler substances by chemical reactions (oxygen, iron, magnesium)
-Compounds: substances that are made up of two or more elements and can be changed into elements (or other compounds) by chemical reactions (water, chocolate chips, sugar)

FOUR STATES OF MATTER:

STATE:	EXAMPLE:	CHARACTERISTICS:
1.) SOLID	Gold	- High density - Density little affected by pressure - Holds its own shape in a container
2.) LIQUID	Water	- High density + little affected by pressure - Adopts shape of its container
3.) GAS	Nitogen	- Low density - Density depends on pressure - Expands to fill its container
4.) PLASMA	Interior of the sun	- Density depends on pressure - Expands to fill its container - Exists only at high temperature

CHEMICAL PROPERTIES
-Substance cannot be observed without altering the substance
- Ex. Flammability

CHEMICAL CHANGES:
Ex.// wood burning, food cooking, rust

PHYSICAL PROPERTIES
-Substance can be observed without altering the identity of the substance
Ex.// Density, colour, melting point

PHYSICAL CHANGES:
Ex.// crushing, tearing

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SEPTEMBER 30, 2009

ELEMENT:
-Substance can not be separated into simpler substances

COMPOUND:
- Two or more elements combined together in a chemical reaction

ELECTROLYSIS: - "to tear apart with electricity"
-An electric current passes through a substance. If the substance is a compound, it will split into two or more elements
Ex.// Waster ---> Hydogen + Water

Elements and compounds are pure substances because it has a unique set of chemical and physical properties.

Posted by: Joanne