Investigative Experiment

Recall …... Sec 1 - students taught and tested on C1 and C2 skills. C1 - using and organising techniques, apparatus and materials (to measure mass and volume of a piece of cork) C2 - observing, measuring and recording (investigating acidity & alkalinity of solutions using different indicators)

Recall ….. Sec 2 - taught and tested C3 C3 - handling experimental observations and data (effect of temperature on the activity of salivary amylase)

C4 - mini investigations Most demanding of the 4 practical skills it involves planning, carrying out and evaluating investigations

Hypothesis... Eg 1- to test the hypothesis that an increase in temperature will increase the amount of solute that can dissolve in a solvent. Eg 2 - to test the hypothesis that dropping a magnet can affect the number of of paper clips attracted to it.

1st step : plan the investigation What to observe and measure What apparatus is needed Which variables to keep constant and which to change How many observations to make

To investigate how solubility depends on temperature Definition : a)Solubility – max amount of solute which can dissolve in a given amount of solvent at a fixed temperature. b)Temperature – degree of hotness or coldness of an object What to observe and measure ? How many observations to make ? Apparatus Beaker, spatula, measuring cylinder, stirrer, thermometer, stopwatch, Materials Common salt, hot water variables constants

Variables Independent variable : the one that is purposely changed Dependent variable : the one that is measured

Controlled variables (constants) The ones that are kept constant

Identifying variables and use of variables Example 1 Title : The effect of dropping of magnet on its strength Problem statement : The aim of this study is to find out if dropping of magnet affect the number of paper clips attracted to it.

Independent variable : Number of times magnet was dropped Trials1111

Dependent variable : Number of paper clips attracted to magnet Constants : Height from which magnet was dropped, size of paper clips, magnet

Quick check …..

To investigate how solubility depends on temperature Definition : a)Solubility – max amount of solute which can dissolve in a given amount of solvent at a fixed temperature. b)Temperature – degree of hotness or coldness of an object What to observe and measure ? The temp of the water has to be measured. To amt of solute (salt) that can dissolve in each temp of water has to be observed. How many observations to make ? cold water tap water hot water as long as all the solutes have dissolved in a given temp. Apparatus Beaker, spatula, measuring cylinder, stirrer, thermometer, stopwatch, Materials Common salt, hot water Variables Independent variable: temperature of solvent (water) Dependent variable : the no. of spoonfuls of solute Constants type of solvent type of solute amount of solvent

Carry out investigations Deal with any inconsistent results by retesting in a systematic way. Suggest modifications to original plan and carry them out if you have the time

Write a report Use the following format : aim apparatus & materials procedure observation and results (tabulate results) conclusion

Example of a table Length (cm) Time (s) Temperature ( o C) No. of spatulaful

Instructions Individual work Form a hypothesis, plan, carry out, write report After briefing, at least 1 week of hands on and “hand-holding”

Deadlines …. Submission of plan (end of term 2) Carry out investigations (during holidays) Reminder : take pictures of your experiment as evidence Submission of report,5 th week of Term 3 (week of 28 th July 2003)

Have fun planning and investigating This powerpoint slides is available at orhttp:// Peicai Sec website.