CIE iGCSE Co-Ordinated Science P1.4 Density Exam Style Questions Paper 3
Question
(a) Table 6.1 shows the audible frequency range of five animals.
(i) State which animal in Table 6.1 can hear a sound with the highest pitch.
(ii) State which animal in Table 6.1 has the smallest audible frequency range.
(iii) State the audible frequency range for a human.
from …………………………………. Hz to …………………………………. Hz
(b) The volume of an elephant is 3.4 m3.
The average density of the elephant is 1030 kg / m3.
Calculate the mass of the elephant.
mass = ……………………………………………. kg
(c) The elephant sprays its skin with water and leaves the water to evaporate.
(i) Describe the process of evaporation in terms of water molecules.
(ii) Suggest why the elephant sprays its skin with water and leaves the water to evaporate.
(iii) During evaporation, liquid water changes state and becomes water vapour, a gas.
Complete the diagrams in Fig. 6.1 to show the arrangement of molecules in liquid water and in water vapour.
▶️Answer/Explanation
Ans : 6(a)(i) bat ;
6(a)(ii) elephant ;
6(a)(iii) 20 (Hz) to 20 000 (Hz) ;
6(b) mass = density × volume (in any form) or 1030 × 3.4 ;
= 3500 (kg) ;
6(c)(i) fastest moving molecules escape ;
from the surface of the liquid ;
6(c)(ii) evaporation has a cooling effect ;
6(c)(iii) liquid – all molecules touching random arrangement ;
gas – molecules widely separated (no more than seven shown) and random arrangement ;
Question
(a) Fig. 6.1 shows an elephant pushing a log up a hill.
(i) State the two quantities that need to be measured to calculate the work done by the elephant on the log.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
(ii) State the form of energy gained by the elephant as it moves up the hill at constant speed.
…………………………………………………………………………………………………………………….
(b) The elephant has a mass of 3500kg and the log has a mass of 180kg.
(i) Calculate the combined weight of the elephant and the tree trunk.
The gravitational field strength, g, is 10N/kg.
weight = ……………………………………………… N
(ii) The volume of the elephant is 3.4m$^{3}$.
Calculate the average density of the elephant.
density = ………………………………………. kg/m$^{3}$
(c) A scientist takes some measurements of the elephant.
Table 6.1 shows the measurements taken.
Complete Table 6.1 with suitable units for these measurements.
One has been done for you.
▶️Answer/Explanation
Ans: 6(a)(i) force ;
distance ;
6(a)(ii) gravitational potential energy ;
6(b)(i) W = mg (symbols or words) or (3500 + 180) × 10 ;
= 36 800 (N) ;
6(b)(ii) density = mass ÷ volume (symbols or words) or 3500 ÷ 3.4 ;
1029 (kg / m$^{3}$ ) ;
6(c)
Question
(a) A person standing on a warm, sunny beach is exposed to several forms of electromagnetic radiation.
Fig. 12.1 shows part of the electromagnetic spectrum.
Complete Fig. 12.1 by writing the names of the other two forms of electromagnetic radiation in the correct places.
(b) The person stands with both feet on some very soft sand on the beach.
When one foot is lifted off the sand, the other foot sinks deeper into the sand.
Explain why this happens.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(c) A sample of sand has a mass of 8000kg.
This sand has a density of 1600kg/m$^{3}$.
(i) Calculate the volume of this sample of sand.
volume = …………………………………. m$^{3}$
(ii) Show that the weight of this sample of sand is 80000N.
The gravitational field strength, g, is 10N/kg.
(d) A piece of glass has been left on the beach. The glass acts like a convex lens focusing the Sun’s rays.
Fig. 12.2 shows two rays of light passing through a convex lens.
(i) Complete the light rays in Fig. 12.2 to show how the light rays are focused by the lens.
(ii) State the name of point F.
…………………………………………………………………………………………………………………….
(iii) On Fig. 12.2, draw a double headed arrow (↔) to indicate the focal length of the lens.
▶️Answer/Explanation
Ans: 12(a)
microwaves in correct place ;
X-rays in correct place ;
12(b) area decreases ;
so pressure increases ;
12(c)(i) volume = mass / density (in any form symbols or words) or 8000 / 1600 ;
= 5 (m$^{3}$ ) ;
12(c)(ii) 8000 × 10 ;
(= 80 000 N)
12(d)(i) rays meet at focus (F) ;
Question
An astronomer observes a large meteorite, a rock from outer space. The astronomer uses a telescope which contains mirrors.
Fig. 12.1 shows the image of the meteorite seen in the mirror by the astronomer.
(a) Select two words or phrases from the list to describe the characteristics of an image formed by a single plane mirror. (Sub-topic – P3.2.1)
▶️Answer/Explanation
The two characteristics of an image formed by a single plane mirror are:
- same size
- upright
(b) The meteorite enters the Earth’s atmosphere.
Fig. 12.2 is a speed-time graph for the meteorite as it approaches Earth.
(i) On Fig. 12.2, label with an S a point when the meteorite is slowing down. (Sub-topic – P1.2)
▶️Answer/Explanation
The meteorite slows down when it experiences air resistance, which occurs after it reaches its maximum speed. Label a point on the graph where the speed starts to decrease.
S somewhere between 5 s and 12 s
(ii) State the form of energy lost by the meteorite as it slows down. (Sub-topic – P1.6.1)
▶️Answer/Explanation
The meteorite loses kinetic energy as it slows down due to air resistance and friction with the atmosphere.
(iii) Use Fig. 12.2 to determine the maximum speed of the meteorite. (Sub-topic – P1.2)
▶️Answer/Explanation
The maximum speed of the meteorite is 36,000 m/s, as indicated by the highest point on the speed-time graph.
(c) The mass of the meteorite is 22,500 kg. The density of the meteorite is 7500 kg/m3.
(i) Calculate the volume of the meteorite. (Sub-topic – P1.4)
▶️Answer/Explanation
Using the formula: Volume = Mass ÷ Density,
Volume = 22,500 kg ÷ 7500 kg/m3 = 3.0 m3.
(ii) A scientist suggests that the meteorite contains metallic iron.
Suggest a simple way for the scientist to test for iron in an object found on Earth. (Sub-topic – C12.5)
▶️Answer/Explanation
The scientist can use a magnet to test for the presence of iron. If the object is attracted to the magnet, it likely contains iron.
(d) The meteorite’s temperature is 1500°C when it falls into the sea. The meteorite loses thermal energy to the water.
(i) State the main method of thermal energy transfer from the meteorite into the water. (Sub-topic – P2.3.1)
▶️Answer/Explanation
The main method of thermal energy transfer from the meteorite into the water is conduction, as the heat is transferred through direct contact between the meteorite and the water.
(ii) Some of the seawater evaporates.
Describe the process of evaporation in terms of the movement and energy of water molecules. (Sub-topic – P2.2.2)
▶️Answer/Explanation
Evaporation occurs when the most energetic water molecules at the surface gain enough energy to escape into the air as gas. This process cools the remaining liquid as the higher-energy molecules leave.
(iii) The meteorite is a solid and the seawater is a liquid.
Draw more circles in the boxes in Fig. 12.3 to show the arrangement and separation of particles in a solid and in a liquid. (Sub-topic – P2.1.1)
▶️Answer/Explanation
In a solid, particles are closely packed in a regular arrangement. In a liquid, particles are close together but not in a fixed arrangement, allowing them to move past each other.
Question
(a) A team of students enter a competition to see who can build the highest tower from identical wooden cubes. One cube has a mass of 200 g. One cube has a volume of 250 cm3.
(i) Calculate the density of one wooden cube.
▶️Answer/Explanation
Solution:
Density is calculated using the formula:
\[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} \]
Given:
Mass = 200 g
Volume = 250 cm3
\[ \text{Density} = \frac{200 \, \text{g}}{250 \, \text{cm}^3} = 0.8 \, \text{g/cm}^3 \]
Therefore, the density of one wooden cube is 0.8 g/cm3.
Answer: 0.8 g/cm3
(ii) Calculate the weight of each wooden cube. Gravitational field strength = 10 N/kg.
▶️Answer/Explanation
Solution:
Weight is calculated using the formula:
\[ \text{Weight} = \text{Mass} \times \text{Gravitational Field Strength} \]
Given:
Mass = 200 g = 0.2 kg
Gravitational Field Strength = 10 N/kg
\[ \text{Weight} = 0.2 \, \text{kg} \times 10 \, \text{N/kg} = 2 \, \text{N} \]
Therefore, the weight of each wooden cube is 2 N.
Answer: 2 N
(b) Fig. 6.1 shows the towers of cubes built by two teams. Team A’s tower is only 6 cubes tall before it falls over. Team B’s tower reaches 10 cubes tall and stays standing.
(i) Use ideas about stability and centre of mass to suggest why team A’s tower falls over.
▶️Answer/Explanation
Solution:
The stability of an object depends on the position of its centre of mass. If the centre of mass is not directly above the base of the object, it becomes unstable and may topple over. In the case of Team A’s tower, the centre of mass is likely not aligned over the base, causing the tower to fall. Team B’s tower, on the other hand, has a centre of mass that is aligned over the base, making it more stable and able to stand taller.
Answer: Team A’s tower falls over because the centre of mass is not directly above the base, making it unstable.
(ii) Explain why more work is done to lift a cube to the top of the tower as the tower gets taller.
▶️Answer/Explanation
Solution:
Work is done against gravity to lift a cube to a certain height. The work done is calculated using the formula:
\[ \text{Work} = \text{Force} \times \text{Distance} \]
As the tower gets taller, the distance (height) that each cube needs to be lifted increases. Therefore, more work is required to lift each cube to the top of the tower as the tower grows taller.
Answer: More work is done because the height (distance) increases as the tower gets taller, requiring more energy to lift each cube.
(iii) State the type of energy that is greater for a cube at the top of the tower compared with a cube lower down the tower.
▶️Answer/Explanation
Solution:
The type of energy that is greater for a cube at the top of the tower is gravitational potential energy. This is because gravitational potential energy depends on the height of the object above the ground. The higher the cube is, the more gravitational potential energy it possesses.
Answer: Gravitational potential energy
(c) One student hits two cubes together. He hears the sound echo from the back wall of the room. The time interval from the student hitting the cubes to the student hearing the echo is 0.25 seconds. The distance to the wall is 39 m.
Calculate the speed of sound through the air.
▶️Answer/Explanation
Solution:
The speed of sound can be calculated using the formula:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \]
Given:
Distance to the wall = 39 m
Time for the sound to travel to the wall and back = 0.25 s
Since the sound travels to the wall and back, the total distance is twice the distance to the wall:
\[ \text{Total Distance} = 2 \times 39 \, \text{m} = 78 \, \text{m} \]
\[ \text{Speed of Sound} = \frac{78 \, \text{m}}{0.25 \, \text{s}} = 312 \, \text{m/s} \]
Therefore, the speed of sound through the air is 312 m/s.
Answer: 312 m/s