1. Properties of Matter
Chapter 2, Section3

2. Chemical & Physical Properties
Chemical properties are about how a substance reacts with another substance to form new substances
Chemical reactions describe how one substance combines and rearranges atoms in order to change into another substance
Reactivity is how a substance changes
Physical properties describe a pure substance.
Physical properties stay the same as long as the substance is the same

3. Chemical Changes
Chemical Changes are changes in the composition of the substance
Atoms rearrange
Becomes a new substance with new properties
Identifying Chemical Changes
New substance formed
Change in energy (up or down)
Smells
Color change

4. Physical Changes
Physical Changes Do Not Change Composition of the Substance
Changes the way it looks
Make smaller/larger particles
Changes from solid/liquid/gas
Properties of the substance do not change
Dissolving is a PHYSICAL Change
Molecules of salt/sugar haven’t changed
Molecules are just surrounded by water molecules

5. Physical Properties of Matter
Extrinsic Properties – depend upon how much of the substance is present
Mass, weight, volume
Intrinsic Properties are the same no matter how much of the substance you have:
Density (mass/volume)
Melting point
Boiling point
Strength
Hardness
Conductivity
Magnetism
Physical Properties can all be MEASURED

6. Density Density is mass/volume
When we say light, we frequently really mean less dense.
When we say heavy, we frequently mean more dense
Compare density by weighting equal volumes of two substances:
Less dense weighs less
More dense weighs more

7. What’s So Important About Density?
Density allows you to know if something will float or sink:
A less dense item will ‘float’ on a more dense item (especially liquids & gasses)
Gasses bubble to the top of a liquid because they are much less dense
Oil floats on water because it is less dense
Buoyancy is the tendency of a less dense substance to rise and float on top of a more dense liquid
Usually water

8. Properties Let Us Determine Uses
Why is copper used for electrical wires?
It has a high measure of conductivity
It is cheaper than the next best alternative (silver)
Why do we use antifreeze in our cars?
It freezes at a much lower temperature than water
It boils at a higher temperature than water

9. Properties of Liquids Boiling point Melting point
Diffusion – thorough mixing without stirring
Very little compressibility
Buoyancy – the buoyant force on an immersed body is equal to the weight of the liquid displaced by the body
Viscosity – resistance to flow

10. Buoyancy
Buoyancy is the relative density, or weight per unit of volume, of the body compared to the fluid determines the buoyant force.
If the body is less dense than the fluid, it will float or, in the case of a balloon, it will rise.
If the body is denser than the fluid, it will sink. Relative density also determines the proportion of a floating body that will be submerged in a fluid.
If the body is two thirds as dense as the fluid, then two thirds of its volume will be submerged, displacing in the process a volume of fluid whose weight is equal to the entire weight of the body.
In the case of a submerged body, the apparent weight of the body is equal to its weight in air less the weight of an equal volume of fluid.
The fluid most often encountered in applications of Archimedes' principle is water, and the specific gravity of a substance is a convenient measure of its relative density compared to water.
In calculating the buoyant force on a body, however, one must also take into account the shape and position of the body.

11. Viscosity Viscosity is a RESISTANCE to flowing
More viscous flows slower
Less viscous flows faster
Viscosity is determined by attraction between particles in a fluid
Which is more viscous – water, syrup, motor oil?
Syrup, then motor oil, then water

12. Tasks for Today Make Sure Everyone has Set Up a User ID
Complete the Density – Slice & Dice Lab
Everyone take the Quiz at the end under your UserID
Complete Density Via Comparison Gizmo
Everyone take the quiz
Work on the Buoyancy Lab (Archimedes Principal)
Take the Quiz