Phases of Matter Chapter 3

Matter and Energy Section 1

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

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

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

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.

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

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

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

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

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”

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

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.

Changes of State Section 2

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.

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!

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

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

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

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!

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

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

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

Phase Changes Phase changes can be shown in a graph

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.