Transcript MATTER
MATTER WHAT THINGS ARE MADE OF! Learning Objectives Students will examine the scientific nature of matter • Describe and identify examples of physical properties/physical changes of matter • Describe and identify examples of chemical properties/chemical changes of matter • Explain what happens to matter during physical and chemical changes • Describe the movement of molecules in solid, liquid and gas states • Describe how energy is involved in change of state Words to Know! matter volume mass weight density physical property solubility ductility malleability chemical property flammability reactivity chemical change solid/liquid/gas viscosity melting/freezing endothermic exothermic evaporation/condensation boiling sublimation MATTER Anything that has mass and takes up space Chemistry is the study of matter – composition structure properties changes it undergoes Properties of Matter Every specific substance has its own combination of properties that are used to identify the substancecharacteristic properties Physical- features you can measure or observe without changing the substance ex. texture, color, shape, mass, volume, hardness, density, What are some physical properties of water?? colorless liquid at room temperature density = 1.0 g/ml melting point boiling point can dissolve many substances Chemical Properties Describes matter based on its ability to change into new substances We can’t always observe the chemical properties – only the chemical changes ex. flammability, reactivity with other substances Changes in Matter Physical changes- alters form or appearance, but does not change into something new. “putting on a costume” analogy Physical Changes A change that affects one or more physical properties of a substance and does not change the identity of the matter •changing a shape •melting an ice cube •sanding a piece of wood •dissolving salt in water Chemical Changes produces a new substance with new & different properties • chemical reaction occurs - atoms rearrange themselves • always involves physical changes • Not easily reversed because the composition has changed • We can learn about chemical properties by looking at the chemical changes that take place Ex. – iron rusting, gasoline burning, baking a cake, electrolysis of water Evidence of Chemical Changes Involves a change in properties and/or energy gas produced – bubbles, foam or fizzing change in color/odor precipitate- solid is produced when 2 solutions are mixed temperature change endothermic- absorbs energy, gets cooler ex. instant cold pack exothermic - gives off energy (heat or light) ex. “hot hands” One Way to Look at It… physical change - printing a word in a different font stampede – stampede stampede chemical change- rearranging the letters to make a new word stampede - made + steps States of Matter State of matter is a physical property There are 4 states: • • • • solid liquid gas plasma The atoms and molecules are always in motion and bumping into each other The particles interact with each other to determine the state Solids Definite shape • Strong attractions keep the atoms locked closely together Definite volume Molecules vibrate slightly-are held closely to each other by particles around it. The strong attraction cannot overcome the motion of the molecules Can be compressed slightly Examples are: salt, diamonds, ice – crystalline solid molecules form regular repeating patterns glass, rubber, wax - amorphous solid no special arrangement or pattern of the molecules Liquids Has no shape of its own- changes to fit the container (weaker attractions) Definite volume Weaker attraction allows molecules to slide and move around each other (flow) Can be compressed some, but not easily Ex. water, mercury Viscosity – the resistance to flow how easily it flows high viscosity – oil, honey low viscosity – water, alcohol Gas No shape of its own – fills its container Volume – changes with its container spreads out until evenly spaced volume can also change with temperature and pressure Molecules move very freely and quickly – high energy and can overcome the weak attractions to each other Behavior of Gases What might happen if the temperature or pressure is changed? temperature is the measure of the average energy due to the motion of the molecules (some molecules move faster than others) thermal energy – is the total amount of energy due to the motion of the molecules pressure - the amount of force exerted on a specific area or surface More gas particles mean more pressure! Boyles Law Gasses can be compressed because there is lots of empty space Describes the relationship between volume and pressure (particles bouncing against container) Inverse relationship: the more pressure, the less volume As the pressure increases, the volume decreases by the same amount (for fixed amount of gas at a constant temperature) Lifting the piston allows the molecules to spread out and increases the volume and decreases the pressure inside Squeezing the piston forces gas molecules closer and decreases the volume and increases the pressure inside Charles’ Law Relates volume and temperature of a gas As temperature increases, volume increases also • Added energy makes the particles move faster and spread out more. Why does the air temperature matter on the day of the Macy’s Thanksgiving parade? Changes in State Substances may change state under certain conditions: • Add/lose thermal energy Heat is the transfer of thermal energy Thermal energy flow from warm to cool When heat flows into a substance, the molecules gain energy and move faster Ex. Ice held in your hand will melt Endo or Exo?? Endothermic – when substance gains or absorbs thermal energy • Heat flows into an object- “warms up” Exothermic – when a substance loses thermal energy • Heat flows out of an object- “cools down” Is an ice cube melting endothermic or exothermic?? changing state… Increase/decrease pressure When you squeeze the molecules closer together, they slow down Ex. Carbon dioxide gas can be made a liquid under pressure Know these Terms! melting freezing vaporization evaporation boiling condensation sublimation **for each of the above – is energy being added or lost for the change to occur?? hint- think about whether the molecules are speeding up or slowing down! Make sure you have read and understood the terms and concepts presented in section 3 of the chapter