1. Unit 1: (2) Physical & Chemical Properties
PHYSICAL SCIENCE 1

2. Physical Property
A characteristic of a substance that can be observed without changing its identity.
can be used to separate mixtures
We use physical properties to help ID materials, choose a material for a specific purpose, or to separate the substances in a mixture.

3. Physical Properties Examples of physical properties:
Viscosity = resistance of a substance to flow
Conductivity = ability of a substance to allow heat or electricity to flow through it
Malleability = ability of a solid to be hammered flat without shattering
Melting point = temp. that a substance changes from a solid to a liquid
Boiling point = temp. that a substance boils
Density = mass per unit volume of a substance (previous notes)

4. Density: The ratio of the mass of a substance to its volume.
Remember:
Density =
Units = g/ml or g/cm3
mass
volume

5. Density is a physical property that can be used to determine a substance’s identity or purity..
METAL
DENSITY (g/cm3)
Aluminum
2.7
Iron
7.9
Lead
11.4
Silver
10.5
What is the identity of a substance with a mass of 15.2 g and a volume of 1.9 cm^3?

6. Physical Properties Some other physical properties: Color Shape
Odor
Size
Texture
Hardness
Mass
Weight
Volume
Phase

7. Viscosity- resistance to flow
The LOWER the viscosity the THINNER the substance. Ex: water
The HIGHER the viscosity the THICKER the substance. Ex: Honey

8. (Thermal) Conductivity- material’s ability to allow heat to flow
Heat travels quickly through conductors such as metals.
Insulators, like wood, plastic, or fabric do not let heat travel through them easily.
They keep heat out (like plastic handles on cookware), or heat in like scarves and sweaters.

9. Malleability and Hardness
Malleability- ability for a substance to be hammered into sheets without shattering (Ex: gold)
Hardness- if the substance will scratch another substance
Ex: diamond
2nd

10. Melting and Boiling points
Melting- Solid to liquid
Boiling- Liquid to gas

11. Separation Techniques
Physical properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture.

12. Using Physical Properties
Filtration- separates materials based on their size.
Distillation- separates substances in a solution based on their boiling points.

13. Physical Changes
Physical change: A change in the form of a substance without changing its identity.
properties remain the same
Reversible (*most of the time*)
can be used to separate mixtures
Examples of physical changes:
Chopping wood Shredding paper
Boiling water Dissolving sugar in water
Words like: crush, smash, tear, evaporate, slice, breakdown, dissolve, absorb, swell, burst

14. Chemical Properties Chemical properties Two examples:
Explains how a substance changes into a new and different substance
Can only be observed when a substance is changing into a different substance
Two examples:
Flammability = matter’s ability to burn in the presence of oxygen
Reactivity = how readily a substance reacts chemically w/ another substance

15. A change in the identity of a substance.
Chemical Change
A change in the identity of a substance.
properties change
irreversible
Signs: color change, formation of a gas/solid, release of light/heat
EX: burning, rusting

16. Examples of chemical changes
Change in color: match, silver, copper
Production of Gas: mentos and coke
Formation of a Precipitate: milk curdling, cottage cheese
Remember: Physical change the composition stay the same, Chemical change the composition changes
Words like: react, burns, forms, decomposed, rusting, sours, rotting, digesting, cooked, molecular change

18. Is a Change Chemical or Physical?
Ask yourself: are different substances present after the changes take place?
NO = Physical change, YES = Chemical change
When matter undergoes a chemical change the composition of the matter changes.
When matter undergoes a physical change the composition of the matter remains the same.

19. Conservation of Mass (and Energy)
It’s the LAW: mass is neither created nor destroyed during a chemical or physical change
Mass of products = mass of reactants
2H2(g) + O2(g) → 2H2O(l)
4 hydrogen
2 oxygen
4 hydrogen
2 oxygen