2023 Cambridge IGCSE Science - Combined (0653) 模拟试题及答案详解

An amylase enzyme is found in human saliva. At which temperature is the rate of starch breakdown catalyzed by this enzyme the highest?

Which cell structure is present in a plant cell but absent in an animal cell?

A substance changes state from solid to liquid. Describe the changes in the arrangement and movement of the particles.

Which statement describes a chemical property of Group I alkali metals?

Dilute hydrochloric acid is added to a test-tube containing solid copper(II) carbonate. Which observations are made?

A runner travels a distance of 1200 m in a time of 5.0 minutes. What is the average speed of the runner?

A sound wave is described as having a high pitch and being quiet. How do the frequency and amplitude of this sound wave compare to a loud sound wave with a low pitch?

A student wants to measure the current flowing through a lamp and the potential difference (p.d.) across it. How must the ammeter and voltmeter be connected relative to the lamp?

An organism detects a change in its environment and responds to it. Which characteristic of living organisms is described by this action?

What is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane?

An enzyme works best at a pH of 2. In which part of the human digestive system is this enzyme most likely to be active?

An atom of sodium has a proton number of 11 and a nucleon number of 23. How many neutrons and electrons are there in a neutral sodium atom?

Copper(II) oxide reacts with hydrogen gas to form copper and water: \( CuO + H_2 \rightarrow Cu + H_2O \). Which statement about this reaction is correct?

Why is copper used to make electrical wiring?

A metal block has a mass of 400 g and a volume of 50 \( \text{cm}^3 \). What is the density of the metal?

A current of 3.0 A flows through a lamp for 4.0 minutes. How much charge passes through the lamp?

An enzyme-catalysed reaction is investigated at different temperatures. The rate of reaction is found to be highest at \(40\text{ }^{\circ}\text{C}\), but drops to zero at \(70\text{ }^{\circ}\text{C}\). What is the explanation for the rate of reaction dropping to zero at \(70\text{ }^{\circ}\text{C}\)?

A green plant is kept in a sealed glass container with plenty of water. It is exposed to bright sunlight for several hours. Which gas will increase in concentration inside the container?

Which statement correctly describes the arrangement and movement of particles in a liquid?

A student reacts marble chips (calcium carbonate) with dilute hydrochloric acid. Which change decreases the rate of this reaction?

An aqueous solution turns universal indicator paper red. What is the pH of this solution?

An object of mass \(15\text{ kg}\) is on the surface of the Earth, where the gravitational field strength \(g\) is \(10\text{ N/kg}\). What is the weight of the object?

Which type of wave is a longitudinal wave?

A lamp is connected to a \(12\text{ V}\) power supply. If the current through the lamp is \(3.0\text{ A}\), what is the electrical resistance of the lamp?

A student sets up an aquatic plant in water under a bright light. Gas bubbles are observed being released from the plant. Which gas is being produced, and which process is responsible?

An enzyme-controlled reaction is carried out at different temperatures: 10 °C, 30 °C, 50 °C, and 80 °C. At which temperature will the enzyme most likely be completely denatured and show no activity?

Which change will decrease the rate of the reaction between dilute hydrochloric acid and calcium carbonate chips?

A student places four different metals into separate test-tubes containing dilute hydrochloric acid. Metal W fizzes rapidly, metal X does not react at all, metal Y fizzes slowly, and metal Z reacts explosively. What is the order of reactivity of these metals, from most reactive to least reactive?

How do the amplitude and the frequency of a sound wave change when the sound becomes louder and has a higher pitch?

A student wants to determine the density of an irregular piece of rock. Which two pieces of apparatus must the student use?

A current of 3.0 A flows through a lamp for 20 seconds. How much electrical charge passes through the lamp in this time?

What is the approximate percentage by volume of nitrogen gas in clean, dry air?

Pepsin is an enzyme found in the human stomach that digests proteins and has an optimum pH of approximately 2. When the stomach contents pass into the small intestine, the pH is raised to about 8 by bile and pancreatic juices. What happens to the activity of pepsin in the small intestine?

A student wants to measure the potential difference across a lamp and the current flowing through it in a simple circuit. How must the voltmeter and the ammeter be connected relative to the lamp?

The reactions of four metals, W, X, Y, and Z, are studied: Metal W reacts vigorously with cold water. Metal X does not react with cold water but reacts with steam when heated. Metal Y does not react with cold water or steam, but reacts with dilute hydrochloric acid. Metal Z does not react with dilute hydrochloric acid. What is the correct order of reactivity of these metals, from most reactive to least reactive?

A solid rectangular block of an unknown metal has a mass of 160 g. Its volume is measured to be 20 cubic centimeters. What is the density of this metal?

Which row shows the correct approximate percentages by volume of nitrogen, oxygen, and other gases in clean, dry air?

Which word equation correctly summarizes the chemical process of photosynthesis in green plants?

Which statement correctly defines the process of osmosis?

Waves can be classified as either transverse or longitudinal. How are light waves and sound waves in air classified?

The temperature of an enzyme-catalysed reaction is increased from 20 °C to 35 °C. Which statement describes the correct explanation for the resulting increase in the rate of reaction?

Which statement describes the effect of carbon monoxide from tobacco smoke on the human body?

An element X reacts with oxygen to form an ionic compound with the formula \(X_2O\). In which group of the Periodic Table is element X located?

The reaction between copper(II) oxide and hydrogen gas is represented by the equation shown: \(CuO + H_2 \rightarrow Cu + H_2O\). Which statement about this reaction is correct?

An unstretched spring has a length of 12.0 cm. When a load of 6.0 N is suspended from the spring, its length becomes 15.0 cm. The limit of proportionality is not exceeded. What is the spring constant of the spring?

A radio station broadcasts a signal with a frequency of 100 MHz. The speed of electromagnetic waves in air is \(3.0 \times 10^8\text{ m/s}\). What is the wavelength of the radio waves?

A circuit contains two resistors connected in parallel across a 12 V battery. The resistances of the two resistors are \(3.0\\ \Omega\) and \(6.0\\ \Omega\). What is the total current drawn from the battery?

Which metal cannot be extracted from its oxide by heating with carbon?

A student measures the rate of an enzyme-catalysed reaction at different temperatures. Which statement correctly explains why the rate of reaction is higher at \(40\ ^\circ\text{C}\) than at \(20\ ^\circ\text{C}\) before the optimum temperature is reached?

An electric motor lifts a load of \(150\text{ N}\) vertically through a height of \(8.0\text{ m}\) in \(4.0\text{ s}\). The total electrical energy supplied to the motor is \(1600\text{ J}\). What is the efficiency of the motor system in lifting this load?

Magnesium reacts with excess hydrochloric acid according to the equation shown:
$$\text{Mg(s)} + 2\text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)}$$
A sample of \(0.12\text{ g}\) of magnesium ribbon is fully reacted with excess acid. What is the maximum volume of hydrogen gas produced, measured at room temperature and pressure (r.t.p.)?
[Relative atomic mass: \(A_r(\text{Mg}) = 24\). The volume of one mole of any gas at r.t.p. is \(24\text{ dm}^3\).]

A circuit contains a \(12\text{ V}\) battery connected to three resistors. Two \(6.0\ \Omega\) resistors are connected in parallel with each other, and this combination is connected in series with a single \(3.0\ \Omega\) resistor. What is the total current flowing from the battery?

Plant cells are placed in a highly concentrated salt solution. Which description of the water potential gradient and the net movement of water is correct?

A wave of frequency \(250\text{ Hz}\) travels from deep water to shallow water. In deep water, its speed is \(2.0\text{ m/s}\). In shallow water, its speed decreases to \(1.5\text{ m/s}\). What is the frequency and wavelength of the wave in shallow water?

Ethene (\(\text{C}_2\text{H}_4\)) contains a double covalent bond between the two carbon atoms and single covalent bonds between carbon and hydrogen atoms. What is the total number of shared electrons in one molecule of ethene?

Four metals, \(P, Q, R,\) and \(S\), are tested as follows:
- Metal \(P\) reacts vigorously with cold water.
- Metal \(Q\) does not react with cold water but reacts with steam.
- Metal \(R\) does not react with steam, but its oxide is reduced by heating with carbon.
- Metal \(S\) does not react with dilute acids and is found uncombined in the Earth's crust.
What is the correct order of reactivity of these metals, from most reactive to least reactive?

Plant cells are placed in a beaker containing a solution with a higher water potential than the cell sap. Which statement correctly describes the movement of water and the final state of the cells?

Which statement correctly describes why the rate of an enzyme-catalysed reaction decreases rapidly at temperatures above the optimum temperature?

Dilute hydrochloric acid reacts with excess calcium carbonate. The concentration of the hydrochloric acid is doubled, while the temperature and mass of calcium carbonate are kept constant. How does this change affect the activation energy and the frequency of successful collisions?

Which metal can be extracted from its oxide by heating with carbon, but does not react with dilute hydrochloric acid?

A toy car of mass \( 500\text{ g} \) is traveling along a horizontal track at a constant speed of \( 12\text{ m/s} \). What is the kinetic energy of the car?

An object is placed in front of a thin converging lens. The distance between the object and the lens is less than the focal length of the lens. What is the nature of the image formed?

Three identical resistors, each of resistance \( 6.0\ \Omega \), are connected in a circuit. Two of the resistors are connected in parallel with each other, and this combination is connected in series with the third resistor. What is the total resistance of this network?

Which row correctly identifies the typical features of sexual reproduction?

A medical scan uses a type of electromagnetic radiation with a wavelength shorter than ultraviolet radiation but longer than gamma radiation. Which row correctly identifies this radiation and its speed in a vacuum?

The reaction between copper(II) oxide and hydrogen gas is represented by the equation:

\[\text{CuO} + \text{H}_2 \rightarrow \text{Cu} + \text{H}_2\text{O}\]

Which statement about this reaction is correct?

A small vehicle of mass \(800\text{ kg}\) is travelling at a constant speed of \(36\text{ km/h}\). What is the kinetic energy of the vehicle?

An enzyme is active at pH 7. When the pH is decreased to pH 2, the rate of reaction drops to zero. Which statement explains this observation?

A circuit contains a \(12\text{ V}\) battery connected in series with two resistors, \(R_1\) and \(R_2\), that are connected in parallel with each other. The resistance of \(R_1\) is \(6.0\ \Omega\) and the resistance of \(R_2\) is \(12\.0\ \Omega\). What is the total current leaving the battery?

Three metals, \(W\), \(X\), and \(Y\), are tested to find their place in the reactivity series.
- Metal \(W\) can be extracted from its oxide by heating with carbon.
- Metal \(X\) reacts violently with cold water to produce hydrogen.
- Metal \(Y\) does not react with dilute hydrochloric acid.

Which list shows the metals in order of decreasing reactivity (most reactive first)?

Three separate food samples are treated with enzymes:
- Amylase is added to Sample 1.
- Protease is added to Sample 2.
- Lipase is added to Sample 3.

Which row correctly identifies the smaller soluble molecules produced in each sample?

A molecule of ethene has the formula \(\text{C}_2\text{H}_4\). What is the total number of shared electrons in all the covalent bonds of one molecule of ethene?

An electromagnetic wave travels through a vacuum with a frequency of \(6.0 \times 10^{14}\text{ Hz}\). What is the wavelength of this wave? (The speed of electromagnetic waves in a vacuum is \(3.0 \times 10^8\text{ m/s}\)).

A student investigates the reaction between calcium carbonate chips and excess dilute hydrochloric acid at \(20\text{ }^\circ\text{C}\). Which change decreases the initial rate of this reaction?

An object of mass \(4.0\text{ kg}\) moves with a constant kinetic energy of \(72\text{ J}\). What is the speed of this object?

The rate of an enzyme-catalyzed reaction decreases rapidly at temperatures above the optimum temperature. Which statement explains this decrease?

A \(6.0\text{ }\Omega\) resistor and a \(3.0\text{ }\Omega\) resistor are connected in parallel across a \(12\text{ V}\) d.c. power supply. What is the total current drawn from the power supply?

Three metal oxides, \(X\text{O}\), \(Y\text{O}\), and \(Z\text{O}\), are heated separately with carbon powder. Oxide \(X\text{O}\) reacts to form metal \(X\) and carbon dioxide. Oxide \(Y\text{O}\) does not react. Oxide \(Z\text{O}\) reacts to form metal \(Z\) and carbon dioxide. Metal \(Z\) is less reactive than metal \(X\). What is the order of reactivity of the metals, from most reactive to least reactive?

Which row correctly identifies a digestive enzyme, the organ where it is secreted, and the product of its reaction?

A molecule of methane, \(\text{CH}_4\), contains covalent bonds. How many shared pairs of electrons are there in one molecule of methane?

A surveyor uses a sound pulse device to measure the distance to a vertical cliff face. (a) State the type of wave that a sound wave is. [1] (b) Explain what is meant by the frequency of a wave. [1] (c) The surveyor sends a sound pulse of frequency 400 Hz. The pulse is reflected back from the cliff face. (i) Explain, in terms of air particles, how a sound wave is transmitted. [2] (ii) The sound wave has a wavelength of 0.85 m. Calculate the speed of this sound wave in air. Show your working and state the unit. [3] (iii) The surveyor hears the echo exactly 1.8 seconds after the pulse is emitted. Calculate the distance between the surveyor and the cliff face. [2]

A student investigates the reaction between solid copper(II) carbonate and dilute hydrochloric acid. (a) Complete the word equation for this reaction: copper carbonate + hydrochloric acid -> [product 1] + [product 2] + [product 3] [2] (b) State the chemical test used to show that carbon dioxide gas is produced, including the positive result. [2] (c) The student performs the reaction twice. Experiment 1: uses large lumps of copper carbonate. Experiment 2: uses powdered copper carbonate of the same mass. State and explain how the rate of reaction in Experiment 2 compares to Experiment 1. Use ideas about particles in your answer. [3] (d) Copper carbonate can also be decomposed by heating it strongly. State the name of this type of chemical reaction. [2]

Amylase is a digestive enzyme that breaks down starch into simpler sugars. (a) Define the term catalyst. [2] (b) Amylase activity was measured at different temperatures. The enzyme activity increased up to 40 degrees C, peaked at 40 degrees C, and then dropped rapidly to zero by 60 degrees C. (i) State the optimum temperature for this amylase enzyme. [1] (ii) Describe and explain the effect on the enzyme activity as the temperature increases from 40 degrees C to 60 degrees C. Use the term denatured in your answer. [3] (c) Digestion of starch occurs in the human digestive system. (i) State the name of one organ where amylase is produced. [1] (ii) State the name of the simpler molecule produced when starch is completely digested by amylase and maltase. [2]

A forklift truck in a warehouse is used to lift a heavy crate. (a) The forklift truck lifts a crate of mass 240 kg vertically upwards through a height of 3.0 m. (i) Calculate the weight of the crate. (The gravitational force on unit mass g is 10 N/kg). [2] (ii) Calculate the work done by the forklift truck in lifting this crate. Show your working and state the unit. [3] (b) The forklift then moves the crate horizontally at a constant speed of 1.5 m/s. (i) State whether any work is being done vertically on the crate while it moves horizontally. Explain your answer. [2] (ii) Calculate the kinetic energy of the crate while it is moving at 1.5 m/s. [2]

A student investigates electrical circuits using a 6.0 V battery and two identical resistors. (a) First, the two resistors are connected in series with the 6.0 V battery. The current in the circuit is 0.15 A. (i) Calculate the total resistance of the circuit. State the unit. [3] (ii) Deduce the resistance of one of these resistors. [1] (b) The student wants to measure the potential difference across one of the resistors. (i) Name the device used to measure potential difference. [1] (ii) State how this device must be connected to the resistor. [1] (c) The student now reconnects the same two identical resistors in parallel with the 6.0 V battery. (i) State how the total resistance of this parallel circuit compares to the series circuit. [1] (ii) Explain how the reading on an ammeter connected next to the battery will change. [2]

Iron is a transition element, whereas sodium is a Group I alkali metal. (a) (i) State two physical properties of iron that are typical of transition elements but are not shown by sodium. [2] (ii) State one chemical property of transition elements shown by iron compounds but not by sodium compounds. [1] (b) Iron is extracted from iron(III) oxide, Fe2O3, in a blast furnace. (i) Name the substance used to reduce iron(III) oxide in the blast furnace. [1] (ii) Write the word equation for this reduction reaction. [2] (c) Steel is an alloy of iron containing carbon. (i) State what is meant by the term alloy. [1] (ii) State why steel, rather than pure iron, is used to build bridges and buildings. [2]

Pregnant women have specific nutritional and health requirements. (a) (i) State two reasons why a pregnant woman requires more iron in her diet. [2] (ii) State one food that is a rich source of iron. [1] (b) Calcium is also highly recommended during pregnancy. (i) State the function of calcium in the development of the fetus. [1] (ii) Name the deficiency disease caused by a lack of calcium or vitamin D in children. [1] (c) Nutrients are transferred from the mother's blood to the fetus across a specialized organ. (i) Name this specialized organ. [1] (ii) State the function of the amniotic sac during pregnancy. [1] (iii) State one substance, other than nutrients and oxygen, that passes from the mother to the fetus across this organ. [2]

The Earth's atmosphere is impacted by human activities. (a) Clean, dry air is a mixture of gases. (i) State the approximate percentage of nitrogen gas in clean, dry air. [1] (ii) Name the noble gas that is present in the largest percentage in clean, dry air. [1] (b) Carbon dioxide and methane are greenhouse gases. (i) State one human activity that increases the concentration of methane in the atmosphere. [1] (ii) Explain how an increase in the concentration of greenhouse gases leads to global warming. [3] (c) Sulfur dioxide is an atmospheric pollutant. (i) State the source of sulfur dioxide in the atmosphere. [1] (ii) Describe one environmental consequence of acid rain caused by sulfur dioxide. [2]

A student investigates the electrical properties of a resistor, \(R\).

(a) (i) State the name of the instrument used to measure the current flowing through resistor \(R\).

(ii) State how a voltmeter must be connected to measure the potential difference across resistor \(R\).

(b) The current in resistor \(R\) is \(0.40\text{ A}\) when the potential difference across it is \(6.0\text{ V}\).

Calculate the resistance of resistor \(R\) and state the unit of your answer.

(c) The student now connects an identical resistor in series with resistor \(R\).

(i) State the effect this has on the total resistance of the circuit.

(ii) Explain how this change in resistance affects the current in the circuit, assuming the potential difference of the power supply remains constant.

(d) Calculate the charge that flows through the circuit when a current of \(0.40\text{ A}\) is maintained for \(2.5\text{ minutes}\). Show your working and state the unit.