1. Physical & Chemical – Properties & Changes

2. Physical Properties Physical Property :
Characteristic of a material that can be observed or measured without changing the composition of the substances in the material.
Examples:
Viscosity
conductivity
malleability
hardness
melting point
boiling point
density

3. Examples of Physical Properties
Viscosity –
Tendency of a liquid to keep from flowing
Thick liquids  high viscosity.
Thin liquids  low viscosity.

4. Examples of Physical Properties
Conductivity -
Ability to allow heat or electricity to flow
Materials that have a high conductivity, such as metals, are called conductors.
Good conductors of heat are usually also good conductors of electricity.

5. Examples of Physical Properties
Malleability -
The ability of a solid to be hammered without shattering
Most metals, such as gold, are malleable.
Solids that shatter when struck are brittle, not malleable.
An ice cube or piece of glass breaks into small pieces when struck with a hammer.

6. Examples of Physical Properties
Hardness - resistance to scratching
One material can scratch another material if it is harder than the other material.
Examples:
A kitchen knife can scratch a copper sheet because stainless steel is harder than copper.
The material used to sharpen the knife blade must be harder than stainless steel.
Diamond is the hardest known material.

7. Examples of Physical Properties
Melting and Boiling Points -
Temperature at which material changes state
Melting point (freezing is same temperature)
Melting  solid to liquid
Freezing  liquid to solid
Boiling point (condensing is same temperature)
Boiling  liquid to gas
Condensing  gas to liquid

8. Examples of Physical Properties
Density –
the ratio of the mass of a substance to its volume (i.e. mass/volume)
Characteristic Property
Density can be used to test the purity of a substance.
Silver has a density of 10.5 g/cm3. A coin with a density of 9.9 g/cm3 is not made from silver, or it contains substances in addition to silver.

9. Physical properties are used to:
Examples of Physical Properties
Physical properties are used to:
Identify materials
Choose materials for a specific purpose
Separate the substances in mixtures.

10. Using Properties to Separate Mixtures
Filtration and distillation are two common separation methods.
Distillation – separates the substances in a solution based on their boiling points.
Examples: gasoline, moonshine

11. Recognizing Physical Changes
Substances in the material remain the same.
Some of the properties of a material change, properties such as: Size, Shape, State of matter (solid, liquid, or gas)
Examples include:
Water going from a liquid to a gas during boiling
Melting butter in a pan
Crumpling a piece of paper
Slicing a tomato

12. Some but not all physical changes can be reversed.
Braiding hair is a reversible change.
Cutting hair cannot be reversed.
Both are physical changes.

13. Chemical Properties
As a candle burns, its compounds combine with oxygen in the air to form water and carbon dioxide.
Chemical property –
ability to produce a change in the composition of matter.
Examples:
Flammability
Reactivity

14. Chemical Properties Flammability Reactivity
A material’s ability to burn in the presence of oxygen.
Materials that burn can be used as fuel.
Reactivity
How readily a substance combines chemically with other substances

15. Chemical Change
Rust forms when oxygen reacts with iron and water. Rust is a brittle, reddish-brown compound. Because iron is highly reactive, you would not choose iron to make jewelry or coins.

16. Recognizing Chemical Change
A chemical change occurs when a substance reacts and forms one or more new substances.
Example:
The color change in a banana peel is caused by chemical changes that are taking place in the cells of the banana.

17. Recognizing Chemical Change
3 common types of evidence for a chemical change:
Change in color
Production of a gas
Formation of a precipitate.

18. Recognizing Chemical Change
Change in Color – a clue that a chemical change may have produced at least one new substance.
Examples:
A shiny silver bracelet that is exposed to air will darken.
As a match burns, it shrivels up and turns black.
A new copper roof and an old copper roof have different colors.

19. Recognizing Chemical Change
A new copper roof has a reddish color.
The green patina on an old copper roof is a mixture of copper compounds.

20. Recognizing Chemical Change
Production of a Gas
Vinegar + Baking Soda  bubbles of carbon dioxide form immediately.
A similar chemical change happens when you use baking powder as an ingredient in a cake recipe.
Bubbles of carbon dioxide expand and cause the cake to rise.

21. Recognizing Chemical Change
Formation of a Precipitate
Precipitate – any solid that forms and separates from a liquid mixture.
Example:
When an acid is added to milk, proteins in the milk undergo a chemical change that causes them to stick together in clumps and form a precipitate  cottage cheese.

22. Chemical Changes
Color change, a gas, or a precipitate DO NOT guarantee that a chemical change has taken place.
When an iron horseshoe is heated, its color changes from gray to red, but the iron is still iron. That means the change is physical, not chemical.

23. Chemical Changes Chemical change:  composition of the matter changes.
Are different substances present after a change takes place? If not, then the change is physical, not chemical.
Chemical change:
 composition of the matter changes.
You got something NEW
Physical change:
 composition of the matter stays same.