Notes 2—Properties of Matter
Mr. PruettWednesday, April 19, 2023
There are four phases of matter:
solid
liquidgas
(plasma—not discussed in this unit)
Properties of Matter
1. Hardness
2. Elasticity
3. Brittleness
4. Malleability
5. Density
6. Viscosity
7. Buoyancy
1. Hardness—Measures a solid’s resistance to scratching
2. Elasticity—measure of a solid’s ability to be stretched and then return to its original size
3. Brittleness—Measures a material’s tendency to shatter upon impact
4. Malleability—Measures a solid’s ability to be pounded into thin sheets
Density–property that describes the relationship between mass and volume.
(how close together the molecules are)
Solids Liquids Gas
Molecules close together
Molecules spread out further
Molecules spread far apart
Mass Volume
Density =
Density of Water = 1 gram1milliliter
If an object with a density of less than 1g/mL is placed in the water, it will _______.float
If an object with a density of greater than 1g/mL is placed in the water, it will _____.sink
BuoyancyBuoyancy• Archimedes was an ancient Greek Archimedes was an ancient Greek
scientist who discovered scientist who discovered that floating that floating objects are supported by an upward objects are supported by an upward force called force called buoyancybuoyancy. .
• Buoyancy—Buoyancy—measure of the measure of the upward force upward force a fluid exerts on an object.a fluid exerts on an object.
• Buoyant force is Buoyant force is equalequal to the weight of to the weight of the liquid that the force displaces.the liquid that the force displaces.
Viscosity—measure of a material’s resistance to
flow.
Not all fluids flow quickly
Viscosity
Some fluids move slowly. They have a high viscosity.
It is very viscous.Syrup pours slowly.
Some fluids move quickly. They have a low viscosity.
Water pours quickly.It is less viscous.
Element—pure substance that cannot be separated into simpler substance by physical or chemical means.
CompoundsPure substance composed of two or more different
elements joined by chemical bonds.
–Made of elements in a specific ratio
that is always the same
–Can only be separated by
chemical means, not physically
Mixtures
• A combination of two or more pure substances that are not chemically combined.
• substances held together by physical forces
• Each item retains its properties
in the mixture
• They can be separated physically
Mixtures
Heterogeneous—a mixture in which every sample might have a different composition.
Homogeneous—a mixture in which every sample has the same composition.
Can you identify the following?
Review before the pictures…
• An element contains just one type of atom.
• A compound contains two or more different atoms joined together.
• A mixture contains two or more different substances that are only physically joined together, not chemically.
Element, Compound, or Mixture?Rocks
Element, Compound, or Mixture?Rocks
Heterogeneous or Homogeneous?
Rocks
Heterogeneous or Homogeneous?
Rocks
Element, Compound, or Mixture?Copper
Element, Compound, or Mixture?Copper
Element, Compound, or Mixture?Jelly Beans
Element, Compound, or Mixture?Jelly Beans
Heterogeneous or Homogeneous?
Jelly Beans
Heterogeneous or Homogeneous?
Jelly Beans
Element, Compound, or Mixture?Table Sugar
Element, Compound, or Mixture?Table Sugar
Element, Compound, or Mixture?Diamond
Element, Compound, or Mixture?Diamond
Element, Compound, or Mixture?Tea
Element, Compound, or Mixture?Tea
Heterogeneous or Homogeneous?Tea
Heterogeneous or Homogeneous?Tea
Element, Compound, or Mixture?Salt
Element, Compound, or Mixture?Salt
Element, Compound, or Mixture?Neon Gas
Element, Compound, or Mixture?Neon Gas
Element, Compound, or Mixture?Salad
Element, Compound, or Mixture?Salad
Heterogeneous or Homogeneous?Salad
Heterogeneous or Homogeneous?Salad
Element, Compound, or Mixture?Pure Water
Element, Compound, or Mixture?Pure Water
Element, Compound, or Mixture?Aluminum
Element, Compound, or Mixture?Aluminum
Element, Compound, or Mixture?Lemonade
Element, Compound, or Mixture?Lemonade
Heterogeneous or Homogeneous?Lemonade
Heterogeneous or Homogeneous?Lemonade
Element, Compound, or Mixture?Silver
Element, Compound, or Mixture?Silver
Element, Compound, or Mixture?Sand
Element, Compound, or Mixture?Sand
Heterogeneous or Homogeneous?Sand
Heterogeneous or Homogeneous?Sand
How is this possible?
SURFACE TENSION—measurement of cohesive energy present at an interphase.
Cohesion: property of like molecules sticking together
What’s going onat the surfaceof a liquid?
What’s going onat the surfaceof a liquid?
Let’s takea look!
Particles that make up a liquid are in constant random motion; they are randomly arranged.
You might expect the particles at the surface to be randomas shown below. (But they aren’t. Why?)
Cohesion!!
= cohesiveattraction
Let’s see how cohesioninfluences the surface:
Under the surface, cohesive attractions pull onindividual molecules in all directions
= cohesiveattractions
= cohesiveattractions
At the surface, pull on the molecules is sideways and downward;there is no cohesive attractions above the molecules
The result of this downward attraction is thatsurface particles are pulled downward:
Surface molecules are compressed more tightly together,forming a sort of skin on the surface, with less distance between molecules than compared to the ones below.
This attractive force also explains the roundedshape that liquids form when droppingthrough the air: The molecules are all being pulled toward the center.
This attractive force also explains the roundedshape that liquids form when droppingthrough the air: The molecules are all being pulled toward the center.
Water has a very highsurface tension.
Question: What property doeswater have that wouldgive it such a strongsurface tension?
Answer: PolarityWater is a “polar” molecule.