[The Effect of Temperature On Surface Water pH]{.underline}

By

Jherri Lansdowne

Katie Linahon

Courtney Stich

Palisades Charter High School

Mr. Engelmann, Science

January 31, 2003

[Abstract]{.underline}

Does the temperature of fresh water have an effect on its pH? Six
schools were chosen from varying latitudes to gain a range of
temperatures from different and climates.

Using GLOBE graphs and tables, the temperature and pH of surface water
from these schools was compared. The data suggested that any sort of
temperature change seemed not to influence pH. After careful analysis of
the schools' data, it seemed that temperature does not affect surface
water pH. This, however, does not agree with standard textbook
explanations. To further the investigation, water samples from a local
stream, as well as, tap water and a vinegar solution were tested for pH
changes at different temperatures. The new experiments agreed with the
textbooks that temperature can affect pH. These experiments demonstrated
the importance of confirming data collected from the field with
measurements conducted under controlled environments.

[Research Question/Hypothesis]{.underline}

When sitting down to pick our research question, our group thought about
different aspects of Earth that we had previously learned a little about
and were further interested in. Water pH happened to be one of them. We
felt that it was an interesting and important subject, which lead us to
wonder what affected pH. This led us to our research question: Does the
temperature of fresh water have an effect on its pH?

pH is the measurement of acidity in water. It has a scale that ranges
from 1 to 14. When more hydroxide ions are present in water it is said
to be basic with a value above 7. When more hydrogen ions present it is
an acid with a value below 7. When the number of hydrogen and hydroxide
ions are equal, the pH is 7, or neutral. Acids and bases control many
chemical reactions in living organisms. Measuring the pH of aquatic
ecosystems is very crucial in monitoring the health of our environment.

The relevance of these facts is unbounded. A myriad of aquatic plants
and animals are very sensitive to changes in pH. Human activities such
as the construction of power plants, dams or even the effects of global
warming may alter the natural water temperature. It is then important to
understand the connection between temperature and pH.

Before doing our project, our group decided that we thought that yes,
water temperature probably does have an affect on pH. Of course, this
was before we began our research.

[Research Method]{.underline}

Logging onto the GLOBE website, we accessed information from six
different schools around the world and looked at the information they
had provided concerning surface water temperature and pH. We decided
that it would be best to use schools from varying climates in order to
increase the range of water temperature. The selected schools were from
Japan, California (USA), Thailand, Cameroon, Poland, and Spain. The
schools were chosen based on their average water temperature and the
amount of hydrology data the school had submitted. The GLOBE graphing
tool was used to combine and analyze pH and temperature data from all of
the six schools.

In addition, water samples from a our local stream along with a sample
of tap water and another of a vinegar solution were tested under
controlled conditions.

[Data Summary]{.underline}

Graph 1: [Surface Water Temperature and pH Data Recorded by Palisades
High School]{.underline} (USA)

![](media/image1.png){width="5.625in" height="3.422222222222222in"}

Graph 2: [Surface Water Temperature and pH Data Recorded by Dara
Academy]{.underline} (Thailand)

![](media/image2.png){width="5.625in" height="3.563888888888889in"}

Graph 3: [Surface Water Temperature and pH Data Recorded by Lycee
Technique (Cameroon)]{.underline}

![](media/image3.png){width="5.625in" height="3.563888888888889in"}

Graph 4: [Surface Water Temperature and pH Data Recorded by Miyagi JHS
(Japan)]{.underline}

![](media/image4.png){width="5.625in" height="3.563888888888889in"}

Graph 5: [Surface Water Temperature and pH Data Recorded by Complex of
Engineering]{.underline} (Poland)

![](media/image5.png){width="5.498611111111111in"
height="3.488888888888889in"}

Graph 6: [Surface Water Temperature and pH Data Recorded by IES Ramon J.
Sender]{.underline} (Spain)

![](media/image6.png){width="5.375694444444444in"
height="3.4138888888888888in"}

[Laboratory Experiments]{.underline}

# **Table 1. Tap Water**

[Before Controlled Temperature Change:]{.underline} [After Controlled
Temperature Change:]{.underline}

[Temp]{.underline} [pH]{.underline} [Temp]{.underline} [pH]{.underline}

Beaker 1 22 7.1 Beaker 1 22 7.1

Beaker 2 22 7.1 Beaker 2 35 7.1

Beaker 3 22 7.1 Beaker 3 15 7.1

**[Table 2. Stream Sample]{.underline}**

[Before Controlled Temperature Change:]{.underline} [After Controlled
Temperature Change:]{.underline}

> [Temp]{.underline} [pH]{.underline} [Temp]{.underline}
> [pH]{.underline}

Beaker 1 22 7.1 Beaker 1 22 7.2

Beaker 2 22 7.1 Beaker 2 50 7.8

Beaker 3 22 7.1 Beaker 3 5 7.1

**[Table 3. Mix: 100 mL Tap Water, 20 mL Vinegar]{.underline}**

[Before Controlled Temperature Change:]{.underline} [After Controlled
Temperature Change:]{.underline}

> [Temp]{.underline} [pH]{.underline} [Temp]{.underline}
> [pH]{.underline}

Beaker 1 22 6.6 Beaker 1 22 7.2

Beaker 2 22 6.6 Beaker 2 70 2.9

Beaker 3 22 6.6 Beaker 3 9 6.8

[Analysis]{.underline}

To solve the intriguing question of the effect of temperature on pH, we
relied on the GLOBE graphs and raw data tables. At first we simply
compared the changes of temperature and pH on each graph. It was
difficult to visualize any patterns on most of

the graphs, so we entered data into an spreadsheet and graphed the
temperature vs. pH (graph 7).

![](media/image7.wmf){width="5.997222222222222in"
height="3.488888888888889in"}

Graph 7. Temperature vs. pH of surface water from six GLOBE schools

Additional spreadsheet graphs were made from the controlled laboratory
tests on stream water, tap water and the vinegar solution (graphs 8, 9
and 10)

![](media/image8.wmf){width="5.8125in" height="2.4722222222222223in"}

Graph 8. Temperature vs. pH of surface water collected from local stream
in California.

![](media/image9.wmf){width="5.8125in" height="2.4770833333333333in"}

Graph 9. Temperature vs. pH of tap water.

![](media/image10.wmf){width="5.875in" height="2.4618055555555554in"}

Graph 10. Temperature vs. pH of vinegar solution.

[Discussion]{.underline}

At first, analyzing the data through the GLOBE graphing tool it is
difficult to come to a conclusion. The relationship between surface
water temperature and pH seems to be random. Each graph, however,
represented data from a different location which did not represent the
full range of temperatures. By entering all the data into a spreadsheet
and then generating a graph it was easier to compare the two variables.
As seen in graph 7, there does not appear to be any relationship between
temperature and pH. With the temperatures ranging between 5 and 31 C,
the pH values remained within a narrow range. The data from the school
in Poland, however, did not agree with this conclusion. Further
background reading in chemistry texts also suggested that there should
be changes in pH with changes in temperature. A simple laboratory
experiment helped to shed some light on the conflicting data. When
comparing the effect of temperature on pH in natural stream water, tap
water and a vinegar solution we came across some interesting results. In
the stream water sample, pH values rose slightly with an increase in
temperature (graph 8). Tap water showed no change (graph 9). And with a
vinegar solution that started off as slightly acidic at room temperature
(6.6), the pH dropped significantly with an increase in temperature
(graph 10).

The new data helped us understand the GLOBE graphs better. In our
laboratory tests, only two variables were present: temperature and pH.
When collecting data from a stream over the course of a year, many other
variables are present that could affect the results. Heavy rainfall,
stagnant water or decomposing leaf litter could all alter the pH at
different times of the year. The chemistry between two separate streams
from different parts of the world can vary widely.

Our investigation illustrates nicely how important it is to verify data
collected from the field with similar tests conducted under controlled
environments. The GLOBE program makes data available to people who would
not normally have access, but it is important to think critically and
verify any conclusions that might be drawn from that data.

> [Conclusions]{.underline}

In five of the six schools from which data was analyzed there is no
apparent relationship between temperature and pH values. Under
controlled conditions, however, temperature can affect the pH of a
solution. In the natural environment hundreds of both natural and
non-natural substances can be present in stream water. Some of these
chemicals will change the pH of water as the temperature changes.

From this we can assume that changes in the surface water temperature of
streams due to human activities can cause changes in pH. These changes
can adversely affect the creatures living in these delicate aquatic
ecosystems.

[Bibliography]{.underline}

**[Graphs:]{.underline}**

-   NASA, NSF, EPA and the U.S. State Department. "The GLOBE Program."

> \<www.globe.gov\> (25 Jan 2003 -- 29 Jan 2003.)

**[Tables:]{.underline}**

-   NASA, NSF, EPA and the U.S. State Department. "The GLOBE Program"

> \<www.globe.gov\> (25 Jan 2003 -- 29 Jan 2003.)

**[Other:]{.underline}**

-   Microsoft® Encarta® Online Encyclopedia 2002. \"pH.\"\
    \<http://encarta.msn.com\> (25 Jan 2003 -- 29 Jan 2003.)

-   Researchers at ph-measurement.co.uk. "pH Measurement Information
    Resource."

> \<http://www.ph-measurement.co.uk/home.htm\> (25 Jan 2003)