Answers
Chapter 1
Test Yourself 1.1 (pg. 8)
1. Chemistry is one of the science fields that studies the structure, properties, composition and interactions
of matter.
2. Preservative, vitamin, pesticide, paint, detergent (any other acceptable answers).
3. Technological development in food preservation (any other acceptable answers).
4. (a) Researcher, doctor, pharmacist (any other acceptable answers).
(b) Biotechnology researcher, farmer, biotechnology engineer (any other acceptable answers).
Brain Teaser (pg. 10)
Add ice to the distilled water and stir the mixture using a thermometer until 10 °C of temperature is obtained.
Test Yourself 1.2 (pg. 11)
1. Scientific method is a systematic method used by scientists and researchers when solving problems in
science.
2. Scientific method helps chemists to solve problems through systematic scientific steps.
3. (Student’s suitable answer)
Hypothesis: The addition of sugar will increase the rate of melting of ice
Manipulated variable: Mass of sugar used
Responding variable: Rate of melting of ice
Fixed variable: Surrounding temperature, type of sugar used, mass of ice
Procedure:
1. Weigh 200 g ice and put in a small pail.
2. Put the small pail in a shaded place for 5 minutes.
3. After 5 minutes, use a measuring cylinder to measure the volume of water formed in the pail.
4. Record the reading in a table.
5. Repeat steps 1 to 4 by adding 10 g, 30 g and 50 g sugar.
Brain Teaser (pg. 16)
No. There are specific methods to get rid of different types of chemical wastes in the laboratory. Chemical
wastes that are thrown directly into the sink or rubbish bin could pollute the environment and endanger
human health.
Test Yourself 1.3 (pg. 18)
1. – Do not play in the laboratory.
– Wear protective equipment when carrying out experiments.
– Do not bring food or drinks into the laboratory.
(any other acceptable answers).
2. (a) A specially designed equipment to carry out experiments that release fumes that are toxic,
flammable or pungent.
(b) Used to wash and clean the body when accidents occur to the body. This equipment is also used to
put out fire that occurs on the body.
(c) Used to protect the body and clothes from spillage of chemicals such as acid, alkali and organic
solvent.
3. Solid residue such as glass and rubber must be thrown in special containers.
4. Oxygen gas – put a glowing wooden splinter into the test tube; the glowing wooden splinter is rekindled.
Hydrogen gas – put a lighted wooden splinter at the mouth of the test tube; a ‘pop’ sound is heard.
5. Repeat the titration until the difference of two volume values does not exceed 0.05 cm3.
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Achievement Test 1 (pg. 20)
1. (a) Salt, sugar, paint, preservative, detergent (any other acceptable answers).
(b) Salt – as flavouring agent or preservative.
Sugar – as flavouring agent or preservative
Paint – used to paint buildings, wood or metal as protection
Preservative – to preserve food so that it can be kept for a longer period
Detergent – used as cleaning agent to remove dirt from clothes
(any other acceptable answers).
2. (a) Agricultural industry, cosmetics industry, medical industry (any other acceptable answers).
(b) Agriculture – provides source of food and income to the country
Cosmetics – provides source of income to the country
Medicine – provides new medicines to the people and improve their quality of life
(any other acceptable answers).
3. Safety glasses – used to prevent dust or chemicals from splashing into the eyes
Laboratory coat – used to protect the body and clothes from chemical spills such as acid, alkali and
organic solvent
Gloves – used when handling chemicals to protect the hands from injury, chemicals or infections
(any other acceptable answers)
4. Making observations ➞ Making an inference ➞ Identifying the problem ➞ Making a hypothesis ➞
Identifying variables ➞ Controlling the variables ➞ Planning the experiment ➞ Collecting data ➞
Interpreting data ➞ Making a conclusion ➞ Writing a report.
5. Precautionary steps to be taken:
1. Inform the teacher or laboratory assistant immediately about the accident.
2. Mark the spillage area as a restricted zone.
3. Sprinkle sulphur powder to cover the spillage
4. Contact the Fire and Rescue Department for further action.
6. (a) To give a different surface area for the cloth.
(b) The larger the surface area of the cloth, the faster the cloth will dry.
(c) Cloth with larger surface area will dry faster than cloth with smaller surface area.
(d) Manipulated variable: Surface area of cloth
Responding variable: Rate of drying of cloth
Fixed variable: Surrounding temperature, type of cloth used, size of cloth
(e) Surface area of cloth (cm2)
25
50
100
Time taken for the cloth to
dry (minutes)
Enrichment Corner (pg. 21)
1. (a) Used gloves, broken conical flask, bromine, concentrated acid
(b) Gloves and conical flask – must be thrown into a special container
Bromine – must be stored in a covered container away from light and heat source
Concentrated acid – must be put in a labelled container and disposed
2. (Student’s suitable answer)
Hypothesis: Soil with acidic pH is not suitable to plant vegetables
Method to control:
Manipulated variable: Type of soil // neutral soil, acidic soil and alkaline soil
Responding variable: Rate of growth of vegetables in soil of different pH
Fixed variable: Type of vegetable, same light intensity
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