MATERIALS Module 01a(i) States of matter States of matter State the distinguishing properties of solids, liquids and gases. Matter • The ‘stuff’ that everything is made from • Made up of particles • http://www.harcourtschool.com/activity/state s_of_matter/ There are three states of matter Relate the properties of solids, liquids and gases to the forces and distances between molecules and to the motion of the molecules • http://lgfl.skoool.co.uk/content/keystage3/ch emistry/pc/learningsteps/SLGLC/launch.html Bonds holding the particles together Very weak bonds vary in strength Changes from one state to another • Need energy because:Particles move faster • This energy is supplied in the form of Heat "Latent heat" is the term used to describe energy which causes a change of state without change of temperature. Sublimation Melting Solidification or freezing Evaporating Condensing Molecular model Describe qualitatively the molecular structure of solids, liquids and gases. • This means you should be able to describe how the particles are arranged in solids, liquids and gases • Supplying or removing heat energy changes the movement of the particles • This changes the arrangement of the particles and therefore the state You can change the state of a substance by heating or cooling it. • When the change is from a liquid to a solid it is called freezing. • When the change is from a gas to a liquid it is called condensing. • When the change is from a solid to a liquid it is called melting. • When the change is from a liquid to a gas it is called boiling or forced evaporation. Relate the properties of solids, liquids and gases to the forces and distances between molecules and to the motion of the molecules. • The particles in solids are held most strongly and move the least • The particles in gases are held together least strongly and move fastest Interpret the temperature of a gas in terms of the motion of its molecules • The higher the temperature the faster the molecules move • http://www.epa.gov/apti/bces/m odule1/kinetics/animation/kani1/ kani104.htm Changes of state Describe qualitatively the pressure of a gas in terms of the motion of its molecules. • It is the force of collision and the number of collisions with the walls of a container that cause gas pressure • This pressure is measured in terms of the force per unit area. Describe qualitatively the effect of a change of temperature on the pressure of a gas at constant volume • As temperature increases • The pressure of gas increases • Because the molecules move faster and hit the sides of the container more frequently Relate the change in volume of a gas to change in pressure applied to the gas at constant temperature and use the equation pV = constant at constant temperature • Pressure is inversely proportional to the volume • As an equation this is P1V1=P2V2 • Where P=pressure & v=volume • 1 & 2 refer to original values and altered values • Or PV = constant. • http://www.grc.nasa.gov/WWW/k12/airplane/aboyle.html Evaporation Describe evaporation in terms of the escape of more energetic molecules from the surface of a liquid. • As molecules are heated they gain energy • The liquid molecules gain enough energy to escape from the surface • This is evaporation • Look at this animation • http://www.absorblearning.com/media/attac hment.action?quick=t1&att=2080 Demonstrate understanding of how temperature, surface area and air flow over a surface influence evaporation. • http://www.ehow.com/info_10041602_experime nts-evaporation-surface-area.html • Higher temp means more energetic molecules – more can escape – more evaporation • More surface area more area over which molecules can escape • Air flows removes evaporated molecules • This means there is more space for molecules to move into – more evaporationevaporate Relate evaporation to the consequent cooling • To change state to a gas the molecules in the liquid need more heat energy • When the molecules escape and the liquid evaporates heat energy is taken from the surroundings • This cools the surroundings • eg water evaporating from your skin cools the skin • Take two thermometers wrap one in dry cotton wool and the other in wet cotton wool • Compare the temperatures after a while Melting and boiling Describe melting and boiling in terms of energy input without a change in temperature. • When a substance melts or boils it has to take in heat energy • When this change of state occurs there is NO change in temperature • http://en.wikipedia.org/wiki/Melting#Thermodynami cs_of_melting State the meaning of melting point and boiling point. • http://www.harcourtschool.com/activity/hotp late/index.html • Melting point is the point at which a substance changes from a solid to a liquid • Boiling point is the point at which a liquid turns to a gas Melting • When a substance melts, some of the attractive forces holding the particles together are broken or loosened • so that the particles can move freely around each other but are still close together. • The stronger these forces are, the more energy is needed to overcome them • and the higher the melting temperature Boiling • When a substance boils, most of the remaining attractive forces are broken so the particles can move freely and far apart. • The stronger the attractive forces are, the more energy is needed to overcome them • and the higher the boiling temperature. Use the terms latent heat of vaporisation and latent heat of fusion and give a molecular interpretation of latent heat. • The energy required to change the state of a substance is known as a latent heat. • The word latent means hidden. • When the state change is from solid to liquid • we must use the latent heat of fusion, and • when the state change is from liquid to a gas, • we must use the latent heat of vaporisation. Distinguish between boiling and evaporation • http://www.vtaide.com/png/boiling.htm Evaporation vs Boiling • Ordinary evaporation is a surface phenomenon • The pressure inside the liquid is equal to atmospheric pressure • Therefore bubbles of water vapour cannot form inside the liquid. • But at the boiling point bubbles of water vapour form inside the liquid • The vaporization becomes a volume phenomena.