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AZ State Standards
• Concept 1: Structure and Properties of Matter • Understand physical, chemical, and atomic
properties of matter. • PO 1. Describe substances based on their
physical properties. • • PO 2. Describe substances based on their
chemical properties. • PO 4. Separate mixtures of substances based on
their physical properties.
Content Objectives
• SWBAT differentiate between pure substances and mixtures by examining whether they can be separated by physical means.
• SWBAT determine the type of mixture by physical properties and whether they separate over time.
Pure Substances
• Substances that contain only one type of element or compound.
Quartz crystals made of pure silicon dioxide (SiO2)
Mixtures • Containing two or more different substances
• Containing multiple types of compounds or elements
Types of Mixtures
• If it is distributed equally it is homogenous.
• If it is unevenly distributed, it is heterogeneous
Mixtures Can Be Separated by Physical Means
• Think about what kinds of physical ways you could separate two substances.
Heterogeneous Mixture • Particles are large enough to be seen, or not
mixed thoroughly enough so that textures and colors can be discerned.
Homogeneous Solution
• Small particles so evenly mixed that individual particles, textures, or colors can not be determined.
Solution • A homogeneous mixture involving an
electromagnetic interaction between molecules.
• Solutions are by definition transparent.
They can be colored, but if you can see through them they are a solution
Colloids • Particles are small enough that they remain
suspended indefinitely.
• But, they are large enough to deflect light making them opaque.
Fog is a colloid of water droplets mixed in air
Milk contains fat droplets in water
Suspension
• Substances separate out over time due to differing densities.
Mud will settle out of water
Oil is less dense than vinegar and rises to the top
Dust will settle out of the air
Can be homogeneous or heterogeneous depending on the particles involved
Precipitate • Precipitates are solids that form during a
chemical reaction between two solutions.
Mixtures • Iron and Sulfur powder in a the mixture
• So, it is hypothesis time:
How can we separate the iron from the sulfur?
Remember, Mixtures Can Be Separated by Physical Means
• Think about what kinds of physical ways you could separate two substances.
Mixtures
• How can we separate the iron from the sulfur?
• Use a magnet!
• Iron is magnetic, sulfur is not...
Mixtures • How can you separate the salt and water?
• So, it is hypothesis time:
Evaporating the Water Off
• Using a change in the state of matter of one, the water turns from liquid to gas, but the salt remains a solid.
Chemical Compounds Are Not Mixtures; They Are Pure Substances
• When two substances combine chemically, they become a new pure substance that can not be separated by physical means.
Turning an iron-sulphur mixture into a Compound
Fe + S FeS Heat
Compounds form as a result of chemical reactions
Iron Sulfide is Not Magnetic
• They can not be separated into iron and sulfur through any physical means.
Differences between compounds and mixtures
MIXTURES COMPOUNDS
1. Mixtures can be separated easily
1. Compounds can not be separated
Differences between compounds and mixtures
MIXTURES COMPOUNDS
1. Mixtures can be separated easily
2. Mixture have the properties of the substances present in it
1. Compounds can not be separated
2. Compounds do not have the properties of the elements
Differences between compounds and mixtures
MIXTURES COMPOUNDS
1. Mixtures can be separated easily
2. Mixture have the properties of the substances present in it
3. No chemical change takes place when a mixture is made
1. Compounds can not be separated
2. Compounds do not have the properties of the elements
3. A compound is always formed due to a chemical reaction
Differences between compounds and mixtures
MIXTURES COMPOUNDS
1. Mixtures can be separated easily
2. Mixture have the properties of the substances present in it
3. No chemical change takes place when a mixture is made
4. There is no heat taken in or given out when a mixture is made
1. Compounds can not be separated
2. Compounds do not have the properties of the elements
3. A compound is always formed due to a chemical reaction
4. Heat is either taken in or given out when a compound is made
Differences between compounds and mixtures
MIXTURES COMPOUNDS
1. Mixtures can be separated easily
2. Mixture have the properties of the substances present in it
3. No chemical change takes place when a mixture is made
4. There is no heat taken in or given out when a mixture is made
5. A mixture can contain elements in any proportion
1. Compounds can not be separated
2. Compounds do not have the properties of the elements
3. A compound is always formed due to a chemical reaction
4. Heat is either taken in or given out when a compound is made
5. A compound always contains the elements in fixed proportions, e.g. FeS contains 7g of iron to 4g of sulphur