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 ?

ApparatusBeaker, spatula, measuring cylinder, stirrer, thermometer, stopwatch,

MaterialsCommon 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 variablesExample 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

Number of times magnet was dropped

0 10 20 30

Trials 1 1 1 1

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 1 1 1

as long as all the solutes have dissolved in a given temp.

ApparatusBeaker, spatula, measuring cylinder, stirrer, thermometer, stopwatch,

MaterialsCommon salt, hot water

VariablesIndependent variable: temperature of solvent (water)

Dependent variable : the no. of spoonfuls of solute

Constantstype of solventtype of soluteamount 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 (oC)

No. of spatulaful

23.4 40.7 34.0 3

23.6 40.6 35.5 4

23.8 40.8 34.5 5

24.0 40.9 35.0 6

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 ,5th week of Term 3

(week of 28th July 2003)

Have fun planning and investigating

This powerpoint slides is available at http://www.angelfire.com/alt/mdm_faridah or

Peicai Sec website.