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Transcript of Unit 2
What are these also called? MOLECULES!! Most often though you will find mixtures A mixture would be Elements AND Compounds MIXED together Fun Fact Can be divided into two catagoriees pure substances and mixtures What matter in it's simplest form? A pure substance Elements and compounds are. What IS a pure substance? Ex. water(?), table salt, gold, and oxygen Mixtures can be separated. All Mixtures share ONE common characteristic What is it? When is a mixture the same? WHEN IT"S A HOMOGENOUS MIXTURE Example: An unopened can of soda. It is evenly spread until you open it. But once opened CO2 escapes. Making it uneven. Key
Concepts What happens at at the molecular level when water melts, freezes and boils? Vanessa Hoffmann :P Unit 2 Temperature 10.2 Temperature uses two scales. Fahrenheit Water freezes at 32 degrees
Water boils at 212 degrees
72 degrees is room temp. Celsius o degrees - water freezes
100 degrees - it boils
used by most scientists & engineers since it is believed to be easier to work with. How do you convert? Converting Between Fahrenheit and Celsius Fahrenheit to Celsius T=9/5T+32 Celsius to Fahrenheit T=5/9(T-32) Key 10.1 10.2 10.3 Molecules are constantly moving? Yes, this includes SOLID objects too!
They aren't FIXED in place but they are actually connected by SPRINGS. Motion = Energy The constant back and forth movement is caused by THERMAL ENERGY. This is Kinetic energy too Temperature measures the kinetic energy per molecule due to random motion Important Thermal energy and temperature are proportionate? YES.
The higher the temp. the faster the molecules move and jiggle. Temperature actually measures a particular kind of kinetic energy per molecule Ex. Electricity Ex. Carbon = Carbon When is a mixture different? When it's a heterogeneous mixture Ex. Chicken Noodle Soup
You never get the same number of stuff in each spoonfull But wait if you throw a rock, the rock gets more kinetic energy but the TEMP. doesn't so.. how can temp. measure kinetic energy then? Well there is a difference between random movement and average movement. Kinetic energy for a collection of many molecules, like a rock, has two parts One of these parts is average motion. This is the WHOLE collection;the WHOLE rock. This kinetic energy is NOT temperature. Each molecule in the rock is also jiggling back and forth. This is RANDOM Random motion is scattered EQUALLY in all directions. Usually when one molecule moves one way the other moves away. THIS Is WHAT TEMPERATURE MEASURES Random Motion Temp. is not affected by average motion. That is why THROWING a rock will not make it hotter. What measures temperature? Thermometers Can detect change in physical characteristics Different thermometers detect different changes When thermometers use liquid it is directly proportionate toincreases in temp. Electrical resistance also changes with temperature A metal wire's resistance will increase with temperature A thermistor is a device that changes it's electrical resistance as temp changes Some digital thermometers sense temp by measuring a thermistor's resistance Some thermometers change color Can only accurately determine temps between 65F and 85F The molecules bump into each other more and more and the structure changes making the crystals change color Absolute Zero The lowest measurable kinetic, not COMPLETELY zero but as close as it can be to zero since molecules never really STOP moving 273C and 459F is absolute zero NOTHING CAN BE LOWER THAN ABSOLUTE ZERO What starts at absolute zero? The Kelvin scale Celsius only measures RELATIVE thermal energy Celsius to Kelvin c+273 Kelvin to Celsius K-273 Is there a Limit to temperature? No. Temperature has no upper limit. Although so weird stuff starts to happen when it gets really hot. Example: AT 10,000 C atoms break apart into separate negative electrons and positive ions forming PLASMA.
Plasma conducts electricity and it makes lighting inside stars. The Phases of Matter 10.3 The phases of Matter Solid Liquid Gas Plasma is matter too but that'll be later Holds it's shape and does not flow Molecules vibrate but do not stray from their place Holds Volume but has no shape -it FLOWS Molecules can move around which is why a liquid FLOWS Unlike a liquids it can not hold volume but it can expand or contract to fill a container They are the farthest apart and have enough energy to completely move away from each other Intermolecular forces Not as strong as chemical bonds
but enough to make molecules attach
to each other
They have different strengths with
different compounds Chemical bonds connect atoms to form a compound Intermolecular forces connect molecules to each other The higher the temperature the lower the intermolecular forces The lower the temperature the higher the intermolecular forces This is how gas is formed This is how solids are formed Liquids are somewhere in the middle Changing phases The melting point is the temp at which things melt Water melts at 0 degrees C
While Iron melts at 1,500
The difference in melting
points tells us that iron's intermolecular
level is stronger than Water's. On the other hand there is... BOILING POINT It is when a liquid turns into a gas The bubbles in water are not AIR but WATER VAPOR This is clearly seen in boiling water BWAAAAAAAAAAAAAAAAAAAAAAA IMMA FIREIN MY LAZA! Elements on Earth are usually in gas
water or a soild form During sublimation a solid can skip liquid phase and go strait to gas. he opposite is deposition T neon and florescent lights make plasma as well but by using electricity.
You also see plasma every time you see lightning! Heterogeneous Suspension Colloid Medium to small particles Can hide self Large Particles that settle Tyndall effect You can see if you shine a light through it Homogenous Solution Water is a universal solvent Solute is BEING dissolved Solvent Mixtures can be broken up Distillation Evaporation Adds heat to evaporate the water and captures the water. May or may not use heat and the water is not captured **Notes are from both class and textbook. Has the most heat of all of the states Freezing Melting vaporization Charles' Law Thermal expiation Direct relationship between heat & temperature Heat Volume Heat Volume Physical Change Chemical Change Can get back Can not get back Ex Burning something Ex Painting something