Notes 2—Properties of Matter Mr. Pruett Monday, August 17, 2015

There are four phases of matter: solid liquid gas (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 gram 1milliliter

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

Buoyancy Archimedes was an ancient Greek scientist who discovered that floating objects are supported by an upward force called buoyancy.Archimedes was an ancient Greek scientist who discovered that floating objects are supported by an upward force called buoyancy. Buoyancy—measure of the upward force a fluid exerts on an object.Buoyancy—measure of the upward force a fluid exerts on an object. Buoyant force is equal to the weight of the liquid that the force displaces.Buoyant force is equal to the weight of 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.

Compounds Pure 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 on at the surface of a liquid?

What’s going on at the surface of a liquid? Let’s take a 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 random as shown below. (But they aren’t. Why?)

Cohesion!!

= cohesive attraction Let’s see how cohesion influences the surface:

Under the surface, cohesive attractions pull on individual molecules in all directions = cohesive attractions

= cohesive attractions

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 that surface 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 rounded shape that liquids form when dropping through the air: The molecules are all being pulled toward the center.

This attractive force also explains the rounded shape that liquids form when dropping through the air: The molecules are all being pulled toward the center.

Water has a very high surface tension. Question: What property does water have that would give it such a strong surface tension? Answer: Polarity Water is a “polar” molecule.