EXPERIMENT: Effect of Dissolved Carbon Dioxide on the pH of water

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HSC BIOLOGY ASSESSMENT TASK 1 Conductor: Wissam Bardouh

HSC BIOLOGY ASSESSMENT TASK 1

MAINTAINING A BALANCE

TASK: OPEN-ENDED INVESTIGATION

Our task is to plan, choose equipment and perform a first hand investigation to demonstrate the effect of dissolved carbon dioxide on the pH of water.

DUE DATE: 21/11/07

CONDUCTOR: Wissam Bardouh

EFFECT OF DISSOLVED CARBON DIOXIDE (CO2) ON PH OF WATER

Introduction:

((Carbon Dioxide is a greenhouse gas. It is everywhere ranging from our bodies to the atmosphere. Carbon dioxide is produced in living organisms as a result of cellular respiration (glucose + oxygen -->carbon dioxide + water + energy). It occurs in high concentrations in the tissues in our body. It then diffuses in the circulatory system where it may be carried in our blood))3. When this blood combines with water and then dissolves, Carbonic acid (hydrogen carbonate ions + hydrogen ions). are formed in the red blood cells which are then carried in the plasma. ((CO2 + H2O --> H2CO3))1. This dissolved carbon dioxide can easily change the pH of water. This carbonic acid is toxic to cells and therefore, whenever carbon dioxide is produced, the body tries to get rid of it before chemical activities are disturbed.

pH is a measurement of how acidic or basic a solution is. Water with pH lower than 7 is considered acidic and higher than 7 is known as basic. The safe levels of pH in drinking water is 6.5 - 8.5. Pure water has a pH of 7 which means there is an equilibrium of positive hydrogen ions and negative hydroxide ions. ((When the pH of water is below 6.5, the water is soft and corrosive. This type of water can damage metal pipes and when used, it can stain clothes, have a sour taste and damage sinks. Water with a Ph greater than 8.5 is considered hard. This water does not pose a health risk, but can stain dishes and utensils))4. When Ph of water is low there can be many consequences and effects. ((Even a moderate decrease in pH of water could affect the fish egg hatching success; irritate fish and worst of all, damage membranes. Water with a pH below 4 or higher than 10 is deadly. It will most likely kill majority of sea creatures. Amphibians are at risk when the pH of water is low. If the pH of water is low, heavy metals will dissolve more readily which will make them even more toxic. When pH is high, ammonium in water is changed to toxic ammonia.)) 2

Hypothesis:

The dissolved Carbon Dioxide will cause the pH of water to decrease.

Risk Assessment:

While conducting this experiment a few safety precautions must be taken in order to prevent any damage to equipment or injuries. Also anything that poses a danger must be dealt with immediately. Some of the hazards and dangers of conducting this experiment and how to prevent them include:

Beakers are made of glass and are dangerous if broken. In order to prevent them breaking, they must be handled with outmost care.

If the water in the beakers is spilt, this will pose a danger as you can slip and injure yourself. Therefore the water must be handled with care and safety precautions must be taken.

Aim:

1- To plan, design, choose equipment and perform a first-hand investigation to demonstrate the effect of varying Carbon Dioxide on the pH of water.

2- To test the hypothesis that dissolved Carbon Dioxide will cause the pH of water to decrease.

Materials:

MATERIALS

QUANTITY

Measuring cylinder

1

Beakers (same size)

1

Stopwatch

1

Distilled water

200mL

Straws

1

pH probe

1

Marker

1

Limewater

50 mL

Safety glasses

1

Gloves

1 pair

Procedure:

Safely glasses and gloves were worn

20mL of limewater blown into and observed to see if it turns milky in order to be assured that Carbon Dioxide was actually being exhaled.

Carefully 50mL of water was poured into each of the 4 test tubes.

The 4 beakers were gathered (one as control and 3 for...
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