ChemistryHowdoessurfacearea and temperatureaffectthe rate of evaporation of salty water and tap water? S
HypothesisFactors that determine how fast a liquid will evaporate:S High temperatureS Large surfaceareaWater has a faster rate of evaporation than salty water
MaterialsS 100 ml beakerS 250 ml beaker S Heat proof matS 1000 ml beaker S Tap waterS Syringe 10ml S Salt waterS Thermometer S TimerS Bunsen burner S Glass rodS Tripod stand with S Weighingbalance gauze
MethodS Add 55ml of water/ salt water to 100ml beaker and heat it for 10 minutes at the boiling point i.e. 100°C.S Record the mass of water/ salt water after 10 minutes.S Repeat the same steps for 250ml and 1000ml beaker with the temperature of 100°C.S Repeat the same procedure for 3 different surface areas at the temperature of 90°C and record the mass of water/ salt water after 10 minutes.
ResultsFor 100°C:Tap water Volume before heating Volume after heating (ml)/±0.5ml for 10 minutes (ml)/±0.5mlBeaker 100 ml 55.0 28.0Beaker 250 ml 55.0 4.0Beaker 1000 ml 55.0 0 (completelyevaporatedat 7:31)Salt water Volume before heating Volume after heating for (ml) 10 minutes (ml)Beaker 100 ml 55.0 17.0Beaker 250 ml 55.0 17.5Beaker 1000 ml 55.0 21.0 (the water was completely evaporated at 10:00)
ResultsFor 90°CTap water Volume before heating Volume after heating (ml)/±0.5ml for 10 minutes (ml)/±0.5mlBeaker 100 ml 55.0 49.2Beaker 250 ml 55.0 41.8Beaker 1000 ml 55.0 21.7Salt water Volume before heating Volume after heating for (ml) 10 minutes (ml)Beaker 100 ml 55.0 48.7Beaker 250 ml 55.0 49.8Beaker 1000 ml 55.0 51.5
ConclusionS Rate of evaporation is the fastest for tap water in 1000ml beaker at 100°C.S Salt water evaporates at a higher temperature than tap water – due to the intermolecular forces between the water molecules and the salt dissolved in it.S the rate of evaporation for salt water in 1000ml beaker at 90°C weighed more than the 100ml and 250ml beaker – against our hypothesis!
EvaluationS Amount of heat/flame of the bunsen burner was not equal for each of the experiment carriedout.S An electronic heating system could have been used so that the level of heat provided is the same for eachexperiment.S The electronic balance with an uncertainty of ±0.001g could have been used for a precised mass of salt added to make the salt solution.
BiologyDoes caffeine and sugar have a strong impact on race times in comparison to water? S
HypothesisProviding the test subjects with 1 l of Cola will make them run faster than when provided with 1 l of water.
Theory behind the bottle rocket When pumped, the air inside the bottle will be compressed. Eventually the pressure will be too high for the cork in the bottle to withstand, thus creating thrust..Hypothetically, when we add mass the initialvelocity will change, causing a shorter distance tobe travelled
2. ProcedureS Fill with 0.6 l of waterS Push in corkS Push in nozzleS PumpS Repeat three times for each mass addedS Record results for eight different masses
ObservationsAs mass was added, range decreased.
EvaluationWe attempted to keep several factors constant: Angle of ramp (40°) Rocket design Amount of water in the rocket Weather conditionsHowever, the rocket didn’t always fly straight. The pressure needed to dislodge the cork is likely to have varied.
Evaluation cont.S In our experiment, the initial velocity decreased as a result of the added mass. Thus the one variable became two variables.S This yielded a shorter range.S There is theoretically (according to v = u + at) no change in the range if initial velocity is kept constant.
ConclusionS Range decreased with amount of mass addedS This is a result of decreasing initial velocity due to added mass, meaning our experiment was not a fair test.