STATES OF MATTER

COMPLETED AS A REQUIREMENT FOR MAVERICK PHYSICAL SCIENCE B. Lee, J. Lee

ATOMS AND MOLECULES IN LIQUID Molecules in a liquid can slide over around each other. The molecules that slide over and around each other is how liquids flow and change shapes. Atoms do not have enough energy to completely break their bonds with another. Liquids have constant volume even though the shape may change.

MOLECULES IN A LIQUID ARE FARTHER APART THAN IN A SOLID AND FLOW PAST EACH OTHER.

ATOMS AND MOLECULES IN GASES Molecules in a gas are free to move around so gas flows. The molecules have much more energy than molecules in a liquid. Each molecule has enough energy to completely break away from its neighbors, which is why gas expands to fill any container. Thermal energy in gases overcome intermolecular forces.

INTERMOLECULAR FORCES Intermolecular forces are a type of force that acts between molecules or atoms that are not bound together by molecules. They are forces together that are attractive and pull molecules together. The competition of thermal energy and intermolecular forces allow the phases of matter to exist. Intermolecular forces bring molecules close. While thermal energy makes molecules vibrate causing them to spread apart.

MELTING The melting point is the temperature when a substance changes from solid to liquid. There are a variety of melting points because the intermolecular forces have different strengths in different materials. The stronger the force is the more energy is obligated to break.

BOILING The boiling point is the temperature at which liquid changes into a gas. When the right amount of thermal energy is added to a liquid, intermolecular forces are entirely overpowered and a liquid becomes a gas. As heat is supplemented a substance may change its form.

EVAPORATION Evaporation happens when molecules go from a liquid to gas at temperatures below boiling point. It happens because temperature measure the average kinetic energy of molecules. The highest-energy molecules have enough energy to break bonds with their neighbors and become a gas if they’re near the surface. The high-energy molecules are what evaporation is.

EVAPORATION COOLS LIQUIDS Energy from evaporations is taken away from a liquid because the molecules that escape are the ones with the most energy. The average energy that molecules left behind is lowered, which is why your body sweats on a hot day. By carrying away energy, evaporation of sweat from your skin cools your body down.

CONDENSATION Condensation happens when molecules go from a gas to liquid at temperatures below boiling point. Water vapor molecules with less than the average energy stick to a cool surface forming drops of water, which is any condensation happens. It raises the temperature of a gas because atoms have more energy than atoms in a liquid.

RELATIVE HUMIDITY The percentage of water vapor is a balance between evaporation and condensation. When evaporation and condensation are exactly balanced, that means the air is saturated. Relative humidity tells how close the air is completely saturated. When the air is completely saturated, water vapor that evaporates from your skin is immediately condensed again.

CONVECTION Convection is the transfer of heat through the motion of fluids such as air and water. Forced convection happens when heat is being carried by a moving fluid. Natural convection happens when the density of a warm fluid becomes lower than the density of surrounding cooler fluid, causing the warmer fluid to float upward.

THE ATMOSPHERE OF EARTH 20.6% of Earth’s atmosphere is made up of oxygen. Air is a thousand times less dense than water. Our atmosphere is made up of different gases. Air is the most important gas in Earth’s atmosphere. Gravity creates pressure because fluids have mass, so they must have weight. Earth’s weather is made up of massive convection currents in the atmosphere. The capability to hold water vapor reduces due to the rapid decrease in temperature, allowing it to condense and create rain.

THE MOLECULAR STRUCTURE OF SOLIDS Thermal energy in a solid is not enough to overcome intermolecular forces of attraction. Atoms in a solid shape are connected by bonds that act like springs. Thermal energy keeps the molecules in the solid moving, but because of intermolecular forces, they only “spring” back and forth around the same average position, which is why solids hold their shape.

SOLIDS HOLD THEIR SHAPE Molecules are bound to each other, which is why all solids have some ability to hold their shape when forces are applied. Solids like steel can hold their shape under greater forces than others like rubber. Solids like plastic have properties between the softness of rubber and the hardness of steel.

STRENGTH AND ELASTICITY Strength is the ability to maintain shape under the application of forces. When you apply a force to an object, it may change its size, shape, or both. A property called elasticity is why rubber bands can stretch many times their original length before breaking. Elasticity is the ability to be stretched or compressed and then return to original size.

BRITTLENESS AND DUCTILITY Brittleness is the tendency to crack or break; the opposite of elasticity. To stretch or shape glass, you need to heat glass until it is almost heated, the molecules move fast, temporarily breaking the forces that hold them together. Ductility is the ability to bend without breaking. A steel fork can be bent in half and the steel does not break because of the steel’s high ductility, which means that steel can be formed in any shape by pounding, rolling, and bending.

CRYSTALLINE SOLIDS Atoms in a solid that are in an ongoing repeating arrangement are called crystalline. Examples of a crystalline solids are salt, mineral, and metal. The most naturally occurring solids on Earth are crystalline. The exterior shape of a crystal reflects the inner placement of atoms and molecules.

CRYSTALLINE SOLIDS The cubic arrangement of chlorine atoms and sodium shapes the crystal. Metals are crystalline, but they may not appear like a “crystal” due to being made up of fused tiny crystals. One of the most important crystalline elements is Silicon. Pure silicon crystals make up most electronic circuits in cell phones, computers, and other devices.

POLYMERS Plastic is everywhere around you. Soft plastic and hard plastic are the two types of plastic. Most plastics are examples of amorphous solids. The difference between amorphous and crystalline solids are that amorphous solids do not have a repeating pattern of molecules and atoms, but crystalline solids do. Plastics belong to a family of materials called polymers. Polymers are materials in which individual molecules are made of long chains of repeating units. Polymers are beneficial because their melting points are well above room temperature, but much lower than most metals.

HEAT CONDUCTION IN SOLIDS Heat conduction is the transfer of heat by the direct contact of particles of matter. Conduction occurs between two materials at different temperatures when they are touching each other. Conduction works through collisions and through the intermolecular forces between molecules.

THERMAL EQUILIBRIUM Thermal equilibrium occurs when two bodies move the same temperature. No heat flows in the thermal equilibrium because the temperatures is the same in two materials.

THERMAL CONDUCTORS AND INSULATORS Solids make the best conductors because the molecules in a solid are packed close together. Thermal conductors are materials that conduct heat easily. Thermal insulators are materials that conduct hear poorly. Silver, copper, gold, and aluminum are good thermal conductors. Heat conduction can’t occur through a vacuum.