Question

SECTION B – CHEMISTRY [40]

QUESTION 4 [20]

4.1 Briefly define the following terms:
4.1.1 Nucleus (1)
4.1.2 Nucleons (1)
4.1.3 Neutrons (1)

4.2 Deuterium and tritium both have the same number of protons and electrons. What makes
them different? (2)

4.3 Complete symbol contain the symbol of the element, the mass number and the atomic number.
Give the complete symbols of Bromide and Bromine. (3)

4.4 Draw the atomic structure of the following element:
4.4.1 H (1)
4.4.2 He (1)

4.5 Locate the following elements in the periodic table, provide their periods; groups and
indicate whether they are metal, metalloid, or non-metal:
4.5.1 Cesium (2)
4.5.2 Germanium (2)
4.5.3 Sulphur (2)

4.6 Use your knowledge of atomic calculations to complete the following chart by stating the   
answers for 4.6.1 – 4.6.8. (4)

QUESTION 5 [20]

5.1 What does pH measure? (1)
5.2 Differentiate between an acid and a base in terms of their pH values. (2)   
5.3 Identify salts, acids and bases applied in the following:
5.3.1 Used as an electrolyte in lead-car batteries (1)
5.3.2 Used as a cleaning agent (1)
5.3.3 Used in drain and oven cleaners (1)
5.3.4 Used in antacids to relieve indigestion (1)

5.4 Complete the following table for bases and acids by giving the answers for 5.4.1 – 5.4.3: (3)   

Chemical name Formula
5.4.1 H3PO4
Sodium hydrogen carbonate 5.4.2
5.4.3 CH3COOH

5.5 Complete the following sentences: 5.5.1 A substance that change colour in the presence of an acid or base ___________ (1) 5.5.2 Bromothymol blue turns ___________in acids and turns ___________ in alkalis. (1) 5.5.3 Red litmus paper turns ___________in a basic media. (0.5) 5.5.4 Blue litmus paper turns ___________in an acid media. (0.5) 5.5.5 Rice grows best in ___________ soil. (1)

5.6 What are the products of the following chemical reactions? 5.6.1 NaOH (aq) + H20 (aq) → (2)

5.6.2 HCl (aq) + H20 (aq) → (2)   

5.7 Complete the following table for common salts by stating the answers for 5.7.1 and 5.7.1: (2)   

Formula Common name 5.7.1 Washing soda NaHCO3 5.7.2


QUESTION 6 [8]

6.1 What do the following consist of:
6.1.1 alpha particle (1)
6.1.2 beta particle (1)

6.2 Why are materials radioactive? (1)
6.3 What is radioactivity? (1)
6.4 When humans are exposed to an overdose of dangerous radioactive materials it can lead
to ________ and __________ . (complete the sentence) (2)
6.5 Which isotope is use in:
6.5.1 examining the lungs (1)
6.5.2 studying the thyroid gland (1)


QUESTION 7   
[12]
7.1 A resultant force is__________ . (complete the sentence) (1)
7.2 Indicate how the magnitude of the resultant force is calculated in each of the following:
7.2.1 When forces are in the same direction. (1)

7.2.2 When forces are in opposite directions. (1)

7.3 Indicate how the direction of the resultant force is determined in each of the following:
7.3.1 When forces are in the same direction. (1)
7.3.2 When forces are in opposite directions. (1)

7.4 Determine the magnitude and direction of the following forces: (3)
2 N east ; 5 N west ; 16 N east ; 15 N south ; 16 N north ; 25 N south ; 14 N north

7.5.1 A metal spring is made of a certain material. Mass pieces of different magnitudes are attached
to the spring to see how much it will stretch as shown below. If the elastic limit is reached at
14 cm on the meter rule, what will we see when another mass piece is added? (2)   




7.5.2 Draw a graph to show the change in the gradient with reference to your answer in 7.5.2 (2)

QUESTION 8 [10]
8.1 Briefly describe how a sound wave is formed. (2)
8.2 Differentiate between wavelength and frequency. (2)
8.3 Pitch is related to amplitude. True OR False. Give a reason for your answer. (2)
8.4 A high pitch sound can be expected from a mouse. True OR False. (1)

  

  
8.5 The speed of a wave can be calculated with “speed of a wave = f
 ” and the period of a wave
can be calculated with “
1
period of a wave =
 . 8.5.1 What is the meaning of the symbol λ? (1)
8.5.2 If a 7 cm wave move at 230 m/s, determine the period of the wave. (use SI units

Answer 1

Question 4

4.1.1. Nucleus: This is the center of an atom where almost all the mass of an atom is concentrated because it contains protons and neutrons each of which has a mass around 1840 times that of an electron.

4.1.2. Nucleons: Protons (positively charged particles) and neutrons (neutral particles) present in the nucleus of an atom are called nucleons.

4.1.3. Neutrons: These are the uncharged (neutral) particles present in nucleus of an atom.

4.2 Deuterium and tritium both have the same atomic number i.e. the same number of protons (and electrons as an atom is neutral). They differ in the number of neutrons. Deuterium has 1 neutron whereas tritium has 2 neutrons. Thus their mass number (sum of protons and neutrons) are different.

4.3. Bromine has atomic number 35 and mass number 80 (from periodic table). So its symbol is

Bromide is formed by gaining of one electron by a bromine atom. So its atomic number and mass number doesn't change as mass of an electron is negligible. Also bromide ion carries a -1 charge as it is formed by gaining of one electron by a neutral bromine atom. So symbol of bromide (ion) is

4.4

4.4.1The first atomic structure is that of H as H has an atomic number 1, so it has 1 proton (the circle in centre represents nucleus) and one electron (represented by dot). It doesn't contain a neutron.

4.4.2.The second atomic structure is that of He as He has atomic number 2, so it has 2 protons (the circle in center represents nucleus) and 2 electrons (represented by dots). Also it has 2 neutrons (n=2).

4.5.1 Caesium (Cs) is in group 1, period 6. It is a metal as group 1 elements have 1 valence electron which can be lost to form a positively charged ion (cation).

4.5.2. Germanium (Ge) is in group 14, period 4. It is a metalloid as it has properties of both metals and non-metals.

4.5.3. Sulphur (S) is in group 16, period 3. It is a non-metal as it has 6 valence electrons and it can gain two electrons to form a negatively charged ion (anion).