# Objectivity in Scientific Observation

In this worksheet, students will work on their scientific skills by looking at objective observations and producing accurate results.

Key stage:  KS 3

Curriculum topic:   Working Scientifically

Curriculum subtopic:   Scientific Attitudes

Difficulty level:

### QUESTION 1 of 10

When scientists observe phenomena around them, it is important that they remain objective. Sometimes, as human beings we tend to see things as we want them to be, so we can prove our point. There is no room for this in science, as that would make the results of an investigation invalid.

Scientific results are accurate when their value is exactly the same as the real quantity. Accuracy is the degree of how close the measurements are to the real quantity. In scientific investigations, measurements are taken at least three times for one quantity. When these measurements are the same or very close to each other, the results are said to be reliable

For the results of a scientific investigation to be precise, they must be the same when the experiment is done under the exact same conditions. Precision is the degree to which this is achieved. If it is achieved the results are of high repeatability and reproducibility. This simply means the investigation can be repeated to reproduce the same results. This makes it scientifically valid.

The thermometers below are used to measure temperature.

What is the lowest temperature these thermometers can measure?

50°

20°

-10°

Alcohol and mercury are two liquids that can be used in glass thermometers. The table gives information about these liquids.

 Liquid Boiling Point (°C) Colour alcohol 78 colourless mercury 357 shiny grey

A red dye is added to the colourless alcohol used in thermometers. Suggest a reason for this.

to help alcohol reach the desired temperature

so that the colourless alcohol becomes visible and we can read the temperature

to make reading the thermometer more fun

Alcohol and mercury are two liquids that can be used in glass thermometers. The table gives information about these liquids.

 Liquid Boiling Point (°C) Colour alcohol 78 colourless mercury 357 shiny grey

Complete the sentences below.

to help alcohol reach the desired temperature

so that the colourless alcohol becomes visible and we can read the temperature

to make reading the thermometer more fun

A mother is very worried about her child's fever. She uses a thermometer to take the temperature. The thermometer reading is shown below:

She is very worried and calls the doctor to say that her child has a temperature over 40° Celsius. The doctor is also very worried and asks the mother to take the child to the hospital.

Did the mother give the doctor an accurate reading?

yes

no

What would be the accurate reading of the thermometer in degrees Celsius?

39°C

39.2°C

39.5°C

Three groups of pupils measure the time it takes for a spoon full of salt to dissolve in 100 ml of water at 30° Celsius. Prior to the experiment, they agree to what they will regard as 'dissolved'.

Their results are shown in the table below. Time is measured in seconds (s).

 Test Number Group A Time/s Group B Time/s Group C Time/s 1 1 1 1 2 1 1.5 3 1.1 1.3 4 0.9 1.1 5 1.1 0.7

Which group produced more reliable results?

Group A

Group B

Group C

Group A from the previous question decided to do the experiment again under the exact same conditions. Their new results are shown on the table next to the old:

 Test Number First experiment Time/s Second experiment Time/s 1 1 1.5 2 1 1.6 3 1.1 1.4 4 0.9 1.5 5 1.1 1.6

Is their experiment precise?

yes

no

If you were looking for evidence on the solubility of salt, would you rely on the results of Group A?

yes

no

Tick three characteristics that make a set of scientific results valid.

repeatable

reproducible

precise

specific

correct

What is the definition of accuracy in scientific investigations?

The results are precise, so they are valid.

The measurements are all different.

The measurements for a quantity are all the same or very close to each other.

• Question 1

The thermometers below are used to measure temperature.

What is the lowest temperature these thermometers can measure?

-10°
EDDIE SAYS
The thermometers can measure temperature in the Celsius and the Fahrenheit scale. You need to look at the Celsius scale. The lowest reading is -10° Celsius.
• Question 2

Alcohol and mercury are two liquids that can be used in glass thermometers. The table gives information about these liquids.

 Liquid Boiling Point (°C) Colour alcohol 78 colourless mercury 357 shiny grey

A red dye is added to the colourless alcohol used in thermometers. Suggest a reason for this.

so that the colourless alcohol becomes visible and we can read the temperature
EDDIE SAYS
Colourless alcohol would not be seen rising in the thermometer. Dyes are added so the alcohol becomes visible. Sometimes in science dyes are added to make the results visible. However, these dyes should not interfere with the properties of the material.
• Question 3

Alcohol and mercury are two liquids that can be used in glass thermometers. The table gives information about these liquids.

 Liquid Boiling Point (°C) Colour alcohol 78 colourless mercury 357 shiny grey

Complete the sentences below.

EDDIE SAYS
Different substances have different properties. There would be no point using an alcohol thermometer to measure temperatures above 78° Celsius, because alcohol would be a gas, so would not rise to show the correct temperature. Mercury, as a liquid metal at room temperature, has really useful properties of expansion and not boiling into a gas until a much higher temperature.
• Question 4

A mother is very worried about her child's fever. She uses a thermometer to take the temperature. The thermometer reading is shown below:

She is very worried and calls the doctor to say that her child has a temperature over 40° Celsius. The doctor is also very worried and asks the mother to take the child to the hospital.

Did the mother give the doctor an accurate reading?

no
EDDIE SAYS
The thermometer reading is very inaccurate as it is far from the real temperature of the child (just above 39°C). The mother was not being objective, because she was very worried for her child's health.
• Question 5

What would be the accurate reading of the thermometer in degrees Celsius?

39.2°C
EDDIE SAYS
To find this you must look carefully and see what number the blue line goes up to. It is not always blue; it depends on what substance is used in the thermometer. The correct answer is 39.2° Celsius.
• Question 6

Three groups of pupils measure the time it takes for a spoon full of salt to dissolve in 100 ml of water at 30° Celsius. Prior to the experiment, they agree to what they will regard as 'dissolved'.

Their results are shown in the table below. Time is measured in seconds (s).

 Test Number Group A Time/s Group B Time/s Group C Time/s 1 1 1 1 2 1 1.5 3 1.1 1.3 4 0.9 1.1 5 1.1 0.7

Which group produced more reliable results?

Group A
EDDIE SAYS
Group A produced more reliable results, because they took 5 measurements and their readings were very close to each other. Group B only measured the time once and Group C repeated the measurement 5 times, but their results are very different to each other.
• Question 7

Group A from the previous question decided to do the experiment again under the exact same conditions. Their new results are shown on the table next to the old:

 Test Number First experiment Time/s Second experiment Time/s 1 1 1.5 2 1 1.6 3 1.1 1.4 4 0.9 1.5 5 1.1 1.6

Is their experiment precise?

no
EDDIE SAYS
Their experiment is not precise. Their results both times are accurate, but if you compare the results from the first experiment to those of the second one, they are different.
• Question 8

If you were looking for evidence on the solubility of salt, would you rely on the results of Group A?

no
EDDIE SAYS
No, the results are not reliable, because they are not precise.
• Question 9

Tick three characteristics that make a set of scientific results valid.

repeatable
reproducible
precise
EDDIE SAYS
Scientific results are valid when they are repeatable, reproducible and precise.
• Question 10

What is the definition of accuracy in scientific investigations?

The measurements for a quantity are all the same or very close to each other.
EDDIE SAYS
For scientific results to be accurate, the measurements for a quantity are all the same or very close to each other.
---- OR ----

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