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.