States of Matter

Mavericks 2013-2014

T.T. and D.R.

Molecules in a Liquid

In a liquid, molecules can slide over and around each other.

Molecules in a Gas

Molecules in a gas move around freely.

The molecules have enough energy to completely break away from its neighbor.

Density of Liquids and Gases

Liquid is more dense than gas.

Molecules in gas move around freely than in a liquid.

Liquid molecules move around freely, but have less space in between them than gas molecules.

Forces in Fluids

The downward force you apply on a fluid creates forces that act sideways as well as down.

Pressure

A force applied to a fluid.

Pressure acts in all directions, not just of the applied force.

The Molecular Explanation

Pressure comes from collision between atoms.

What Intermolecular Forces Do

There are two types of forces.

The strongest force is between atoms that are bonded together.

Properties of Intermolecular Forces

Two Types of Forces that Act Between Atoms The strongest forces are between

atoms that are bonded together into molecules

The weaker type of force acts between

molecules.

The Role of Thermal Energy

The phases of matter exist only because of competition between thermal energy and intermolecular forces.

Intermolecular forces always try to bring molecules close.

Explaining the Phases of Matter

When molecules have a lot of thermal energy, intermolecular forces are completely overcome and the molecules spread apart as in gas.

Melting Point

The temperature at which a substance changes from a solid to a liquid.

Stronger forces require more energy to break.

Boiling

When enough thermal energy is added.

The substance will boil over.

Changes in State Require Energy

It takes energy to overcome intermolecular forces.

As you add more heat the substance will change its state.

Range of Melting and Boiling Points

Melting points and boiling points are essential to life.

Some things ewe need solid and others liquid.

Water is less dense in solid form

Solid materials have a higher density.

Water is an exception, because sold water has an open crystal structure.

Decreasing Density

As water freezes the molecules separate slightly.

This causes the volume to increase, but the mass stays the same.

Evaporation

Occurs when molecules go from liquid to gas at a temperature below boiling point.

Happens because temperature measures the average kinetic energy of the molecules.

Evaporation Cools Liquids

Evaporation takes away energy from a liquid.

The average energy left behind is lowered.

Relative Humidity

Air contains water vapor.

Evaporation adds water vapor to the atmosphere.

Condensation removes water vapor.

Condensation

Occurs when molecules go from gas to liquid at temperature below boiling point.

Condensation occurs because water vapor molecules with less than average energy stick to a cool surface forming drops of liquid water.

What is convection?

Convection is the transfer of heat through the motion of fluids such as air and water.

Natural Convection

Natural Convection occurs because fluids expand when they heat up.

Density of a warm fluid becomes lower.

Air is not “nothing”

Air feels light because it is 1000x less dense than water.

Even though air is 1000x less dense than water it still has mass and weight.

Air is a Mixture of Gases

Molecular Nitrogen and Oxygen account for 97.2% of the mass of air.

Atmospheric Pressure

The Earth’s atmospheric pressure is due to the weight of air even though the density of air is very low.

Weather

Created by Gigantic convention current in the atmosphere.

Warm air, warmed by the sun, rises and cool air sinks which causes winds or convection.

How Rain Forms

At high altitude the temperature decreases.

As the temperature drops the ability to hold water drops causing rain.

Why Solids are Solids

Individual molecules are bound tightly, so they do not change positions as they do in liquids and gases.

Solids Hold Their Shape

Because solids molecules are bound together they can hold their shape when force is applied.

Some can hold against stronger forces than other.

Physical Properties of Solids

Density Strength Elasticity Ductility Thermal Conductivity Electric Conductivity

The meaning of strength

When you apply force to an object it may change shape, size, or both.

Strength of an object is the ability to maintain its size and/or shape under pressure.

Elasticity

Describe a solid ability's to be stretched then returned to its original size.

Brittleness

Brittleness is the tendency of a solid to crack or break.

Glass is a very good example, you cannot stretch glass even one tenth of a percent.

Ductility

The most useful property of metals is that they are ductile.

Steel is high in ductility, this means steel can be formed into useful shapes.

Crystalline solids

The atoms in crystals can move around, this how geodes and salts are formed.

If the atom repeats its pattern the solid is called a crystalline.

Many solids are crystalline

Most solids on earth are crystalline.

The crystalline form come s from the atoms and how they form a cubic shape.

Multicrystals solid

Steel is a crystalline.

But they don’t all look like crystals.

Metal is made up of tiny crystals fused together in a jumble.

Crystal silicon

The most important element in crystalline is silicon.

Almost all the electronic circuits in phones, computers, ETC, are all made from pure silicon.

Plastics

Almost everything we see is made of plastic .

Plastic is made with an extremely wide range of physical properties.

Some plastics are soft, some hard, and some slippery.

Amorphous solids

Most of the plastics made are an examples of amorphous solids.

Amorphous is Greek for without shape.

Polymers

Plastics belong to the family called polymer.

Polymers are materials in which individual molecules are made of long chains of repeating units.

Why polymers are so useful

They have a boiling point above room temperature.

In their liquid state polymer can be molded very easily.

What is conduction

Heat conduction is the transfer of heat by the direct contact of particles of matter

Conduction occurs between two materials at different temperature

Thermal equilibrium

As a collision happens, the molecules of the hotter material looses energy and the molecules of the cooler material gains energy, eventually the material will become the same temperature.

Which state of matter conducts best

Conduction can also occur in liquids and gases, but solids makes the best conductor for heat.

Thermal conductor and insulator

Materials that can conduct heat easily are called thermal conductors.

Good electrical conductors are copper, silver, gold, and aluminum.

Heat conduction cannot occur through a vacuum

Conduction cannot occur in a vacuum of space when there is no matter

A thermos can keep a liquid hot for hours using a vacuum.