Chapter 1 - Scientific Processes

Question 1

Name the tests and the results for the following chemicals:
- water
- carbon dioxide
- alkali
- acid
- oxygen
- pH of a solution

Answer 1

• blue cobalt (II) chloride paper (turns pink)
• clear lime water (turns milky) / hydrogen carbonate indicator (turns yellow/orange)
• red litmus paper (turns blue)
• blue litmus paper (turns pink)
• glowing splint (reignites)
• universal indicator solution/paper

Question 2

Name 4 things you must do for correct labelling

Answer 2

1. Labelling must be in pen
2. Lines may not cross
3. No arrows used
4. Never underline labels

Question 3

What is an independent variable?

Answer 3

The variable that the experimenter changes.

Question 4

What is the dependent variable?

Answer 4

The variable being measured in the experiment.

Question 5

What is the constant?

Answer 5

It is the controlled variable.

Question 6

Name the tests and the results (if present) for the following foods:
- sugar
- starch
- proteins
- fats
- vitamin C

Answer 6

• Benedict’s solution:
  (orange-redish: large amount)
  (greenish-yellow: small amount)
  (stays blue: no sugar present)
• Iodine solution
  (turns from orange-brown to dark blue-black: present)
• Biuret solution
  (turns purple/violet: present)
• ethanol
  ( forms milky white suspension: present)
• DCPIP
  (blue colour disappears: present)

Question 7

What is the formula for magnification?

Answer 7

magnification = size of drawing /
actual size of image

Question 8

Name the 5 errors.

Answer 8

• instrumental error
• observational error
• human error
• systematic error
• random error

Question 9

What is a instrumental error and how can it be prevented?

Answer 9

It occurs when the instruments used are not functioning correctly as they should.
Ensure the instrument are calibrated correctly before using it.

Question 10

What is an observational error and how can it be prevented?

Answer 10

It is when the experimenter did not read the instrument used correctly when recording results.
It can be prevented by repeating the experiment and calculating an average.

Question 11

What is a human error and how can it be prevented?

Answer 11

Human error can occur when instruments are not used or read correctly.
- spilling / sloppiness
- bad calculations / wrong formulas
- reading a measuring device incorrectly
- not cleaning equipment
- using the wrong chemical
- not following the planned procedure

Question 12

What is a systematic error and how can it be prevented?

Answer 12

It is errors caused by the way in which the experiment was conducted.
It can be prevented by taking more measurements and calculating an average, or by changing the way the experiment was conducted.

Question 13

What is a random error and how can it be prevented?

Answer 13

It this errors that are unknown and unpredictable.
It can be reduced by averaging a sufficiently large number of measurement results.