planning a solubility investigation.pptx

Chemistry-variables in an investigation

1. PLANNING A SOLUBILITY INVESTIGATION MEASURING THE CHANGE IN SOLUBILITY WHEN TEMPERATURE CHANGES

2. VARIABLES Different factors or things that could affect (change) the result of an investigation or experiment.

3. DISSOLVING SALT IN WATER-FACTORS THAT COULD AFFECT THE RESULT TEMPERATURE OF THE SOLVENT: Salt will dissolve faster in hot water than in cold water. Hotter the water, faster is the dissolving of salt. AMOUNT OF SALT: More the amount of salt we use, less is the rate of dissolution. At higher temperatures, we can dissolve more salt. VOLUME OF THE SOLVENT More the amount of water, more is the rate of dissolution.

4. IT IS IMPORTANT TO KEEP THE VOLUME OF WATER SAME. This is to make sure that we get accurate results. Since we are measuring the solubility at different temperatures, we have to keep the volume of water the same, otherwise we will not get correct measurements that cannot be compared.

5. MEASURING THE SOLUBILITY OF SALT IN 50 cm 3 AT DIFFERENT TEMPERATURES We measure the maximum number of spatulas (spoons) of salts that can be dissolved in 50 cm 3 of water at different temperatures ranging from 20 to 80 ℃. Here, the variable we change is the temperature of water. The variable we measure is the number of spatulas of salt that can dissolve in water at different temperatures (or solubility ). The solubility of salt in water will increase with increase in temperature. This variable is therefore dependent on temperature. The volume of water is kept the same for each temperature. It is kept constant .

6. The variable that you change is called the independent variable (temperature in this case) The variable that we measure is called the dependent variable (in this case, the solubility) The variable that we keep the same is called the control variable (in this case the volume of water)

7. PLOTTING A GRAPH FOR THE INVESTIGATION Horizontal axis: independent variable (temperature) Vertical variable: dependent variable (solubility)

8. TEMPERATURE SOLUBILITY OF SALT IN 50 CM3 OF WATER 20 ℃ 18g 30 ℃ 26g 40 ℃ 35g 50 ℃ 44g 60 ℃ 54g 70 ℃ 64g 80 ℃ 78g