Liquids and Solids PDF

Lesson 3 Liquids and Solids  Focus What are the properties of Question liquids and solids? New viscosity crystalline solid Vocabulary unit cell amorphous solid allotrope surface tension...

Lesson 3 Liquids and Solids  Focus What are the properties of Question liquids and solids? New viscosity crystalline solid Vocabulary unit cell amorphous solid allotrope surface tension surfactant  Two types of forces intramolecular forces hold atoms together in Intermolecular or molecules and polyatomic ions. attractive forces: Forces that holds molecules together (exist between molecules) A hydrogen bond is an attraction between two atoms of two molecules. One of the atoms is hydrogen, while the other is oxygen, nitrogen, or fluorine.  Infer the reason that the liquid is at the same level in each of the interconnected tubes.  Liquid take the shape of their container but its volume is fixed According to the kinetic-molecular theory: - Forces of attraction between particles in the liquid limit their range of motion so that the particles remain closely packed in a fixed volume. - individual particles do not have fixed positions in the liquid. The particles can flow to adjust to the shape of a container, but the liquid cannot expand to fill their container like gases Other properties Density includes Compression Viscosity Cohesion and adhesion Surface tension Capillarity Density liquids are much denser than gases For example, liquid water is about 1250 times denser than water vapor at 25 ° C and 1 atm of pressure. The presence of intermolecular forces holds the particles closer to each other making the liquid denser Compression Unlike gases, liquids are considered incompressible in many applications. Enormous amounts of pressure must be applied to compress liquids by very small amounts because liquid particles are already tightly packed.  In a given volume: Gas Liquid Less particles More particles Number of particles More space between particles Less space between particles Amount of space No attractive forces between Intermolecular forces between particles Attractive particles forces Fluidity Gases and liquids are classified as fluids because they can flow and diffuse Liquids usually diffuse more slowly than gases at the same temperature, because intermolecular attractions interfere with the flow. Thus, liquids are less fluid than gases. A comparison between water and natural gas can illustrate this difference. When there is a leak in a basement water pipe, the water remains in the basement unless the amount of water released exceeds the volume of the basement. When a gas is leaked, it won’t stay in the basement, it will diffuse through all the area.  have you ever tried to get honey out of a bottle?  Viscosity is a measure of the resistance of a liquid to flow Viscosity The particles in a liquid are close enough for attractive forces to slow their movement as they flow past one another. High viscosity 🡪 slow flowing It is determined by: Low viscosity 🡪 fast flowing type of intermolecular forces size and shape of particles temperature A. Attractive Forces In typical liquids, the stronger the intermolecular attractive forces, the higher the viscosity. B. Particle Size and Shape more massive molecules will Molecules with long chains, such as have a greater viscosity. cooking oils and motor oil, have a higher viscosity than shorter, more-compact molecules assuming the molecules exert the same type of attractive forces. Did you ever wonder why syrup that is stored in the refrigerator is harder to pour than syrup stored in the pantry? You probably know that warming syrup makes it pour more easily. But why does an increase in temperature help?  C. Temperature Increasing temperature decreases viscosity because the added energy allows the molecules to overcome intermolecular forces and flow more freely. When you pour a small amount of cooking oil into a frying pan, the oil tends not to spread across the bottom of the pan until you heat it. With the increase in temperature, there is an increase in the average kinetic energy of the oil molecules. C. Temperature Motor oil keeps the moving parts of an internal combustion engine lubricated. Because temperature changes affect the viscosity of motor oil, people once used different motor-oil blends in winter and summer. Steel float or sinks in water? Water spiders can walk on water, why?  Intermolecular forces do not have an equal effect on all particles in a liquid. Particles in the middle of the liquid can be For particles at the surface of the liquid, there attracted to particles above them, below are no attractions from above to balance those them, and to either side. from below. (exhibit stronger attractive forces) Thus, there is a net attractive force pulling down on particles at the surface. Surface Tension It is a measure of the inward pull by particles in the interior. "The property of the surface of a liquid that allows it to resist external force” In general, the stronger the attractions between particles, the greater the surface tension. Water has a high surface tension because its molecules can form multiple hydrogen bonds.  Soaps and When the Compounds Dirt water alone particles detergents decrease bonds are that lower the cannot the surface tension broken, the cannot surface tension remove the of water by water spreads penetrate dirt from disrupting the out allowing the of water are the surface skin and hydrogen bonds dirt to be of water called clothing. between water carried away by drops. molecules. the water. surfactants.  When water is placed into a narrow container, such as the glass tubes, you can see that the surface of the water is not straight. There are two types of forces at work: cohesion and adhesion. Cohesion and Adhesion Cohesion Adhesion Is the force of attraction Is the force of attraction between between identical molecules. molecules that are different.  meniscus: the curved surface of a column of liquid adhesive forces GREATER cohesive cohesive forces forces GREATER than adhesive forces the water rises along the inner walls of the cylinder A convex meniscus A concave curves up toward meniscus curves you. down away from you.  If the cylinder is extremely narrow, a thin film of water will be drawn upward. This movement of a liquid such as water is called capillary action, or capillarity. Narrow tubes are called capillary tubes.  Capillary action is the upward movement of liquid into a narrow cylinder, or capillary tube.  Capillary action helps explain how paper towels can absorb large amounts of water. The water is drawn into the narrow spaces between the cellulose fibers in paper towels by capillary action. Did you ever wonder why solids have a definite shape and volume?  have a definite shape and volume Solids Solids contain particles with strong attractive forces. Particles in a solid vibrate in a fixed position. Thus, there is more order in a solid than in a liquid. Because of this order, solids are not fluid.  Density of Solids In general, the particles in a solid are more closely packed than those in a liquid. Thus, most solids are more dense than most liquids. When the liquid and solid states of a substance coexist, the solid almost Solid cubes of benzene sink in liquid benzene because always sinks in the liquid. solid benzene is more dense than liquid benzene.  One exception to this is water. Ice cubes and icebergs float because water is less dense as a solid than it is as a liquid. WHY? each H2O As a result, the water molecules molecule can As in ice are form hydrogen water less-closely bonds with up to freezes, packed together four neighboring than in liquid molecules. water. Types of solids  Amorphous solids An amorphous solid is one in which the particles are not arranged in a regular, repeating pattern. It does not contain crystals. Example of an amorphous solid:  Amorphous solids An amorphous solid is one in which the particles are not arranged in a regular, repeating pattern. It does not contain crystals. An amorphous solid often forms when a molten material cools too quickly to allow enough time for crystals to form.  Crystalline solids A crystalline solid is a solid whose atoms, ions, or molecules are arranged in an orderly, geometric structure. The locations of particles in a crystalline solid can be represented as points on a framework called a CRYSTAL LATTICE. Crystalline solids A unit cell is the smallest arrangement of atoms in a crystal lattice that has the same symmetry as the whole crystal.  seven categories S LL of crystals based on shape CE IT UN e th IZE OR Crystal shapes differ because EM the surfaces, or faces, of unit M cells do not always meet at right T NO angles, and the edges of the DO faces vary in length. Categories of crystalline solids Crystalline solids can be classified into five categories based on: 1- the types of particles that they contain 2- how those particles are bonded together  Atomic Solids Covalent Metallic solids network solids Categories of Crystalline Solids Molecular solids Ionic solids  Categories of Crystalline Solids The only atomic solids are noble gases. Atomic Their properties reflect the weak dispersion forces between the atoms. Solids Ar  Categories of Crystalline Solids Metallic consist of positive metal ions surrounded by a solids sea of mobile electrons.  Categories of Crystalline Solids Metallic consist of positive metal ions surrounded by a solids sea of mobile electrons. The mobile electrons make metals: Malleable Ductile good conductors of easily hammered into shapes easily drawn into wires heat and electricity.  Categories of Crystalline Solids Covalent Atoms such as C and Si, which can form multiple network covalent bonds, can form covalent network solids. solids The covalent network structure of quartz, which contains silicon, is shown in Figure below. Figure 19 The most common kind of quartz has a hexagonal crystal structure.  Categories of Crystalline Solids Covalent Atoms such as C and Si, which can form multiple network covalent bonds, can form covalent network solids. solids Carbon forms three types of covalent network solids: Buckminsterfullerene An element, such as carbon, that exists in different forms at the same state—solid, liquid, or gas—is called an allotrope  Categories of Crystalline Solids Covalent Atoms such as C and Si, which can form multiple network covalent bonds, can form covalent network solids. solids Carbon forms three types of covalent network solids:  Categories of Crystalline Solids Molecular In molecular solids, the molecules are held together solids by different types of intermolecular forces. Most molecular compounds are not solids at room temperature.  Categories of Crystalline Solids Molecular In molecular solids, the molecules are held together solids by different types of intermolecular forces. Because they contain no ions, molecular solids are poor conductors of heat and electricity.  Categories of Crystalline Solids Ionic It consists of cations and anions. solids Each ion in is surrounded by ions of opposite charge.  Categories of Crystalline Solids Ionic It consists of cations and anions. solids Each ion in is surrounded by ions of opposite charge. When ionic crystals are struck, the cations and anions are shifted from their fixed positions. Repulsions between ions of like charge cause the crystal to shatter. Categories of Crystalline Solids  Types of Crystalline Solids Type Unit Particles Characteristics of Solid Phase Examples soft to very soft; very low melting Atomic atoms Group 18 elements points; poor conductivity fairly soft; low to moderately high I2, H2, O, NH3, CO2, Molecular molecular melting points; poor conductivity C12H22,O11 (table sugar) Covalent atoms connected very hard; very high melting points; diamond (C) and network by covalent bonds often poor conductivity quartz (SiO2) hard; brittle; high melting points; Ionic ions NaCl, KBr, CaCO3 poor conductivity atoms surrounded soft to hard; low to very high Metallic by mobile valence melting points; malleable and all metallic elements electrons ductile; excellent conductivity