2. T.T. and D.R.

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

4.  Molecules in a gas move around freely.  The molecules have enough energy to completely break away from its neighbor.

5.  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.

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

7.  A force applied to a fluid.  Pressure acts in all directions, not just of the applied force.

8.  Pressure comes from collision between atoms.

9.  There are two types of forces.  The strongest force is between atoms that are bonded together.

10. 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.

11.  The phases of matter exist only because of competition between thermal energy and intermolecular forces.  Intermolecular forces always try to bring molecules close.

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

13.  The temperature at which a substance changes from a solid to a liquid.  Stronger forces require more energy to break.

14.  When enough thermal energy is added.  The substance will boil over.

15.  It takes energy to overcome intermolecular forces.  As you add more heat the substance will change its state.

16.  Melting points and boiling points are essential to life.  Some things ewe need solid and others liquid.

17.  Solid materials have a higher density.  Water is an exception, because sold water has an open crystal structure.

19.  As water freezes the molecules separate slightly.  This causes the volume to increase, but the mass stays the same.

20.  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.

21.  Evaporation takes away energy from a liquid.  The average energy left behind is lowered.

22.  Air contains water vapor.  Evaporation adds water vapor to the atmosphere.  Condensation removes water vapor.

23.  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.

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

25.  Natural Convection occurs because fluids expand when they heat up.  Density of a warm fluid becomes lower.

26.  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.

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

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

29.  Created by Gigantic convention current in the atmosphere.  Warm air, warmed by the sun, rises and cool air sinks which causes winds or convection.

30.  At high altitude the temperature decreases.  As the temperature drops the ability to hold water drops causing rain.

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

32.  Because solids molecules are bound together they can hold their shape when force is applied.  Some can hold against stronger forces than other.

33.  Density  Strength  Elasticity  Ductility  Thermal Conductivity  Electric Conductivity

34.  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.

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

36.  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.

37.  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.

38.  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.

39.  Most solids on earth are crystalline.  The crystalline form come s from the atoms and how they form a cubic shape.

40.  Steel is a crystalline.  But they don’t all look like crystals.  Metal is made up of tiny crystals fused together in a jumble.

41.  The most important element in crystalline is silicon.  Almost all the electronic circuits in phones, computers, ETC, are all made from pure silicon.

42.  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.

43.  Most of the plastics made are an examples of amorphous solids.  Amorphous is Greek for without shape.

44.  Plastics belong to the family called polymer.  Polymers are materials in which individual molecules are made of long chains of repeating units.

45.  They have a boiling point above room temperature.  In their liquid state polymer can be molded very easily.

46.  Heat conduction is the transfer of heat by the direct contact of particles of matter  Conduction occurs between two materials at different temperature

47.  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.

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

49.  Materials that can conduct heat easily are called thermal conductors.  Good electrical conductors are copper, silver, gold, and aluminum.

50.  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.