Exercise 2.1
Essay questions: Answer the questions that follow:
SR1 SCD
SR1 SCB
SR1 SCD
Exercise 2.2
SR1 SCB and SR1 SCD
Find the mistakes in the following answers provided and correct them accordingly. The number of mistakes is indicated in the bracket [ ].
Example: What is chemistry? [2]
Chemistry is the study of the composition, structure, chemical properties and interactions of particles.
Answer: Chemistry is the study of the composition, structure, properties and interactions of matter.
1. What is 'matter'? [2]
Matter is tiny and discrete particles. It has a mass and occupies space. Matter also runs in a zig-zag motion.
Answer: Matter is made up of tiny and discrete particles. It has a mass and occupies space. The particles of the matter always run in a zig-zag motion.
2. Define a melting point. [3]
Melting point is when a solid becomes a liquid. For example, the melting point for water is 0.
Answer: Melting point is the temperature at which a solid becomes a liquid as it absorbs heat/energy. For example, the melting point for water is 0 degree celsius.
3. Why is the temperature constant when a solid is melting? [4]
The solid absorbs heat energy and the temperature rises. When it has sufficient energy, the energy will break all the attractive forces between matter and thus all the energy is used up. Therefore, the temperature remains constant. This is called the freezing point. At this time, solid and gas are present in the system.
Answer: The solid absorbs heat energy and the temperature rises. When it has sufficient energy, the energy will overcome the attractive forces between the particles of the matter and thus all the energy is used up. Therefore, the temperature remains constant. This is called the melting point. At this time, solid and liquid are present in the system.
4. Briefly describe subatoms. [4]
An atom has got three subatomic particles, namely proton, electron and neutron. A proton is a positively charged atom which weighs 1. An electron is negatively charged and it has no weight at all. The neutron weighs 1 and it is neutral. Protons and neutrons are located in the nucleus. Electrons circulate the cell in the shells. As each atom has the same number of protons and neutrons, so the atom is always neutral.
Answer: An atom has got three subatomic particles, namely proton, electron and neutron. A proton is a positively charged particle which weighs 1. An electron is negatively charged and it has a weight of 1/1840 (~ 0). The neutron weighs 1 and it is neutral. Protons and neutrons are located in the nucleus. Electrons circulate the nuclues in the shells. As each atom has the same number of protons and electrons, so the atom is always neutral.
5. What is meant by isotope? Why is it important in daily life? [3]
Isotope is a thing that has the same number of electrons but a different number of neutrons with another atom of the same element. The stable isotope such as cobalt-60 is useful to treat cancers.
Exercise 2.3
SR1 SCB and SR1 SCD
1. The following diagram shows an experiment conducted in a laboratory.
Copper sulfate granules were placed in two test tubes packed with gel. One of the tubes was inverted as shown in the diagram. Both of the tubes were observed in 2 days.
d) What would have happened in Test tubes A and B? [2]
e) What process could be observed in Test tube A? [1]
f) Explain how the process took place in Test tube A. [2]
g) What process has taken place in Test tube B? [1]
Essay questions: Answer the questions that follow:
SR1 SCB
Use the theories of Matter to describe the following phenomena.
- Ali can smell the broth being cooked by his neighbour. [3]
- An ice cube in a container will take the shape of the container when it is melting. [4]
- Hot gas causes high pressure against the glass wall of a container. [3]
- When 0.1 cm3 water is transferred into a glass syringe which is heated to 100oC, the plunger will be pushed out for about 100 cm3. Explain why this phenomenon is observed. [5]
- What will happen if the syringe is cooled to 50oC. [5]
Answers:
SR1 SCB
- The broth contains many molecules that always move in Brownian motion [1]. The freshly cooked broth has highly kinetic molecules which move rapidly through the spaces between the air molecules [1] in the atmosphere from Ali's neighbour's kitchen to his nose. This process is called diffusion [1].
- The ice cube is maintained in its square form when the attractive forces between the water molecules are strong. As the cube absorbs heat from the atmosphere, the energy will overcome the attractice forces [1], releasing many molecules that move in clusters as a liquid [1]. As the whole matter becomes generally looser than its solid due to the poor attractice forces [1], the liquid tends to take the shape of the container because they are no longer held firmly at their fixed positions [1].
- Gas contains many tiny and discrete particles [1]. When it is heated, the particles will absorb energy which in turn speed up their zig-zag movements [1]. As they move in a random manner, the particles will collide with each other as well as the inner wall of the container [1]. Hence, it causes high pressure inside the container.
SR1 SCD
- Water contains many tiny and discrete particles (molecules) [1]. When the glass syringe is heated, the water will absorb energy from the source [1]. The water particles will move even faster until 100oC at which the boiling point is achieved. At this time, the energy is used to break down all the attractive forces between the water molecules [1], releasing them as gas particles (steam) [1]. As the particles are now far apart, hence they take up even more space in the syringe [1]. As a result, the plunger will be pushed out.
- When the steam is cooled to 50oC, much energy is released [1]. In a cooler environment, the molecules will come closer and the steam/gas will condense to liquid [1]. This will allow the formation of attractive forces between the particles to form droplets of liquid [1]. The space previously taken up by the gas is now empty [1]. The user can now compress/push the plunger very easily [1].
Exercise 2.2
SR1 SCB and SR1 SCD
Find the mistakes in the following answers provided and correct them accordingly. The number of mistakes is indicated in the bracket [ ].
Example: What is chemistry? [2]
Chemistry is the study of the composition, structure, chemical properties and interactions of particles.
Answer: Chemistry is the study of the composition, structure, properties and interactions of matter.
1. What is 'matter'? [2]
Matter is tiny and discrete particles. It has a mass and occupies space. Matter also runs in a zig-zag motion.
Answer: Matter is made up of tiny and discrete particles. It has a mass and occupies space. The particles of the matter always run in a zig-zag motion.
2. Define a melting point. [3]
Melting point is when a solid becomes a liquid. For example, the melting point for water is 0.
Answer: Melting point is the temperature at which a solid becomes a liquid as it absorbs heat/energy. For example, the melting point for water is 0 degree celsius.
3. Why is the temperature constant when a solid is melting? [4]
The solid absorbs heat energy and the temperature rises. When it has sufficient energy, the energy will break all the attractive forces between matter and thus all the energy is used up. Therefore, the temperature remains constant. This is called the freezing point. At this time, solid and gas are present in the system.
Answer: The solid absorbs heat energy and the temperature rises. When it has sufficient energy, the energy will overcome the attractive forces between the particles of the matter and thus all the energy is used up. Therefore, the temperature remains constant. This is called the melting point. At this time, solid and liquid are present in the system.
4. Briefly describe subatoms. [4]
An atom has got three subatomic particles, namely proton, electron and neutron. A proton is a positively charged atom which weighs 1. An electron is negatively charged and it has no weight at all. The neutron weighs 1 and it is neutral. Protons and neutrons are located in the nucleus. Electrons circulate the cell in the shells. As each atom has the same number of protons and neutrons, so the atom is always neutral.
Answer: An atom has got three subatomic particles, namely proton, electron and neutron. A proton is a positively charged particle which weighs 1. An electron is negatively charged and it has a weight of 1/1840 (~ 0). The neutron weighs 1 and it is neutral. Protons and neutrons are located in the nucleus. Electrons circulate the nuclues in the shells. As each atom has the same number of protons and electrons, so the atom is always neutral.
5. What is meant by isotope? Why is it important in daily life? [3]
Isotope is a thing that has the same number of electrons but a different number of neutrons with another atom of the same element. The stable isotope such as cobalt-60 is useful to treat cancers.
Exercise 2.3
SR1 SCB and SR1 SCD
1. The following diagram shows an experiment conducted in a laboratory.
A lobule of potassium hydroxide was placed in a beaker containing water. After 24 hours, the lobule went missing.
a) What has occurred in the beaker? [1]
b) How would you prove the answer given in (a)? [2]
c) Suggest a way that can speed up the process shown in this experiment. [1]
d) What would have happened in Test tubes A and B? [2]
e) What process could be observed in Test tube A? [1]
f) Explain how the process took place in Test tube A. [2]
g) What process has taken place in Test tube B? [1]
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