Phases of Matter Chapter 3 1 Matter and

Phases of Matter Chapter 3 1

Matter and Energy Section 1 2

Let’s Review! • Matter is… – Anything that has mass and takes up space – Can be a pure substance… • Element or compound – Or a mixture… • Homogeneous or heterogeneous – Made of… • Atoms and molecules 3

Kinetic Theory • Energy: the ability to change or move matter, or to do work. • Kinetic Energy: energy of motion • Kinetic Theory of Matter: – ALL matter is made of atoms and molecules – These atoms and molecules act like tiny particles that are always in motion 4

Kinetic Theory • Because all particles of matter are in motion, they all have kinetic energy! • The higher the temperature, the faster the particles move. • At the same temperature, more massive particles move slower than less massive ones 5

Temperature • Particles of matter are constantly moving, but they don’t all move at the same speed, therefore, some have more kinetic energy than others • Temperature: a measure of the average kinetic energy of the particles in an object. 6

Thermal Energy • Thermal Energy: total kinetic energy of the particles that make up a substance • Temperature versus thermal energy – Temperature is average kinetic energy – Thermal energy is determined by the amount of a substance 7

Phases of Matter • Matter can be classified as a solid, liquid, gas, or plasma • This is determined by whether or not the shape and volume are definite or variable 8

Solid • Solid: atoms/molecules can only vibrate in one place, occasionally slide by one another. – students in a detention fidgeting in their seats • Shape: definite • Volume: definite • Energy: low • Crystalline Solid: atoms arranged in a regular repeating pattern – Salt, diamonds • Amorphous Solid: No repeating pattern – Wax, glass 9

Liquid • Liquid: atoms/molecules can move about freely – students in the cafeteria • Shape: variable • Volume: definite • Energy: mid-level • Surface Tension: Attraction of molecules at the surface of a liquid – this causes liquids to form spherical drops • Viscosity: resistance to the flow of a liquid – low = runny – high = thicker, like honey 10

Gas • Gas: atoms/molecules move around wildly constantly running into each other. – football practice • Shape: variable • Volume: variable • Energy: High • Because the particles in liquids and gases can move past each other they are considered “fluids” 11

Plasma • 4 th and most common phase of matter in the universe • Shape: variable • Volume: variable • Energy: highest (the particles are electrically charged) • Affected by magnetic fields 12

Plasma • They act like gases but have some differences – plasma can conduct electric current while gases do not • Commonly found in stars, can be created naturally by lightning on Earth and in the hottest part of a very hot flame. 13

Changes of State Section 2 14

Phase Changes • Change of state or a phase change is a conversion of a substance from one phase (solid, liquid, or gas) to another. • The identity of the substance does not change, but the amount of energy does. 15

Phase Changes • Law of Conservation of Mass: Mass cannot be created or destroyed, it is conserved for all physical and chemical changes • Law of Conservation of Energy: Energy cannot be created or destroyed • Energy can change forms during physical or chemical changes, but the total amount present before and after is the same – IF energy of a substance changes it is because it came from another source! 16

Phase Changes • Adding energy, in the form of heat, causes particles to move FASTER – Solid Liquid Gas • Removing energy causes particles to move SLOWER – Gas Liquid Solid 17

Phase Changes • Some phase changes require energy – Melting, evaporation, sublimation • Some phase changes release energy – Boiling, condensation, deposition • A change in energy often means a change in temperature also 18

Melting • Solid Liquid • Melting Point: the temperature at which a substance changes from solid to liquid. • Melting point depends on the pressure. 19

Evaporation • Liquid Gas • Boiling Point: the temperature at which a liquid turns into a gas • When humans sweat (a liquid), heat from the body or surroundings causes evaporation • When the water evaporates, the molecules take their heat energy with them, which creates a cooling effect on the body! 20

Sublimation • Solid Gas – Solid carbon dioxide (dry ice) goes from solid to gas – Ice cubes can go from ice to gas while still in the freezer 21

Condensation • Gas Liquid • Condensation Point: the temperature at which a gas becomes a liquid • Fog is caused by condensation, the water gas particles clump, energy is released from the particles, and their movement slows down 22

Freezing • Liquid Solid • Freezing Point: temperature at which a liquid becomes a solid 23

Phase Changes • Phase changes can be shown in a graph 24

Phase Changes • During a change of state, temperature is constant • The temperature won’t begin to change until the phase change is completed – All of the solid has melted, all of the liquid has evaporated, etc. 25