Contents · State the properties of solids, liquids and gases. ... As the mass of the particles...

Topic 1: The Particulate Nature of Matter.............................. 1

Topic 2: Experimental Techniques ........................................15

Topic 3: Atoms, Elements and Compounds ........................34

Topic 4: Bonding-the structure of matter.............................47

Topic 5: Chemical Calculations .............................................71

Topic 6: Chemical Reactions .................................................95

Topic 7: Electricity and Chemistry .....................................126

Topic 8: Chemical Energetics .............................................152

Topic 9: Acids, Bases and Salts ..........................................171

Topic 10: The Periodic Table ................................................207

Topic 11: Metals and the Reactivity Series ..........................224

Topic 12: Air and water .........................................................246

Topic 13: Ammonia, Sulfur and Carbonates .......................268

Topic 14: Organic Chemistry ................................................287

Answers .................................................................317

Contents

400_IGCSE-Chemistry-215-275_FinalPrint.pdf 17/05/19

Topic

1The Particulate Nature of Matter

The Particulate Nature

of Matter1

Core

Я State the properties of solids, liquids and gases.

Я Describe the structure of solids, liquids and gases in terms of particle arrangement and movement.

Я Describe changes of state in terms of melting, boiling, evaporation, freezing, condensation and sublimation.

Я Describe qualitatively the pressure and temperature of a gas in terms of the movement of its particles.

Я State Brownian motion as evidence for the kinetic particle (atoms, molecules or ions) model of matter.

Я Describe and explain diffusion.

Extended

Я Explain changes of state in terms of the kinetic theory.

Я Describe and explain Brownian motion and state evidence for Brownian motion.

Я Describe and explain dependence of rate of diffusion on molecular mass.

The Kinetic Particle Theory states that:

ţţ All matter consists of tiny moving particles like atoms, molecules or ions.

ţţ There is forces of attraction between the particles and the particles possess kinetic energy to vibrate or move about.

ţţ All matter can exist as solids, liquids or gases depending on the arrangement of the particles.

States of matter

Solid:

ţţ In the solid state, the particles are closed to one another and they are arranged in regular arrangement. This gives solid a definite shape and definite volume. There is strong attractive forces of attraction between the particles so they can only vibrate in fixed positions.


IGCSE Chemistry2

Liquid:

ţţ In the liquid state, the particles are further apart compared to the solid state and they are not arranged in a regular arrangement. A liquid will take the shape of its container. A liquid has a definite volume and cannot be compressed. The forces of attraction between the liquid particles is weaker than the forces of attraction between the solid particles, hence liquid particles are able to move around and slide past one another.

Gas:

ţţ In the gaseous state, the particles are furthest apart. A gas does not have any definite shape or volume and gases can be compressed easily. The forces of attraction in gases is weaker than in liquids, hence gas particles are able to move around freely.

ţţ All gases exert a pressure due to the constant collision between the gas particles as well as against the walls of the container. The pressure of a gas depends on the temperature and volume of the container. At a higher temperature, the gas particles possess greater kinetic energy; they move faster and hit against the wall of container more frequently, resulting in greater pressure. For the same amount of gas at a fixed temperature, the pressure of the gas is inversely proportional to the volume of its container.

Solid Liquid Gas

Particles arrangement and movement

Particles are held closely in a regular arrangement. Particles vibrate in fixed position.

Particles are further apart compared to the solid state and they are free to move.

Particles are further apart compared to the liquid state and they are free to move.

Volume and shape Has a definite shape and volume.

Has a definite volume but takes the shape of its container.

Has no definite volume and takes the shape of its container.

Regular arrangementof particles in a solid

Liquid particles movefurther apart and

slide past one another

Gas particles movefreely and quickly.


The Particulate Nature of Matter3

Changes of state

According to the Kinetic Theory of Matter, when matter is heated, the particles gain more kinetic energy and move faster or vibrate more. The matter also expands as its particles move further apart. Physical changes between the different states can occur when heat energy is given out (exothermic) or taken in (endothermic) from the surroundings as shown in diagram below:

(I) Melting: Conversion of solid into liquid state

Melting is an endothermic physical change where heat is taken in from the surroundings. When a solid is heated, its particles vibrate faster. At the melting point, the solid particles gain enough energy to break free from the regular arrangement and change into liquid.

(II) Evaporation and Boiling: Conversion of liquid into gaseous state

Evaporation and boiling are endothermic physical changes where heat is taken in from the surroundings. When a liquid is heated, the liquid particles gain more energy. Some of the attractive forces between particles is broken and particles move further apart to form a gas. Evaporation occurs on the surface of liquids at any temperature while boiling occurs only at the boiling point of the liquid. During evaporation, the high energy particles escape from the surface of the liquid, even at temperatures below its boiling point.

(III) Condensation: Conversion of gas into liquid state

Condensation is an exothermic physical change where heat is given out to the surroundings. When a gas is cooled, the gas particles lose their kinetic energy and move slowly. The attractive forces hold the particles closer to form a liquid.

melting

freezing

condensingboiling/

evaporating

subliming

condensing

liquid

solid gas


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(IV) Sublimation: Conversion of solid directly into gaseous state

Sublimation is an endothermic physical change where heat is taken in from the surroundings. When a solid like iodine or ammonium chloride is heated, its particles vibrate faster. The forces of attraction between particles is broken and the particles move further apart to form a gas.

Heating curve

Note that the temperature remains constant during the state changes. Eg: solid to liquid.

Brownian motion

ţţ The gas and liquid particles are moving in a random zigzag motion, known as Brownian motion. Brownian motion results from the random molecular bombardment of visible particles by invisible particles.

ţţ Evidence of Brownian motion is shown by the random movement of dust particles seen under the microscope. The dust particles are constantly being bombarded by the invisible particles in the air.

Diffusion

ţţ Diffusion describes the process in which particles spread by colliding randomly with one other. During diffusion, the particles move from a region of high concentration to a region of low concentration.

ţţ Diffusion occurs fastest in gas followed by liquid as the gas particles move faster than liquid particles.

Boiling

Solid

Melting

Freezing

Gas

Condensing

Solid and liquid exist

Mel

ting

poin

tB

oilin

gpo

int

Liquid and gas exist

Liquid

Tem

pera

ture

Time

Brownain Movement


The Particulate Nature of Matter5

Evidence for diffusion:

In liquids: diffusion of potassium manganate(VII) in a beaker of water.

In gases: diffusion of perfume vapours in the air and diffusion of reddish-brown bromine gas.

Factors affecting the rate of diffusion:

(a) Temperature

As temperature increases, the rate of diffusion increases as the particles now possess greater kinetic energy and move faster.

(b) Molecular mass of particle

As the mass of the particles increases, the rate of diffusion decreases as more energy is required to move the particles.

The effect of molecular mass on diffusion can be seen from the position of the ammonium chloride ring formed in the diagram below. As NH3 gas is lighter (Mr = 17.0) than HCl gas (Mr = 36.5), NH3 gas travels faster and moves a greater distance than HCl. Hence, the white ring of ammonium chloride, NH4Cl, is formed closer to cotton soaked in concentrated HCl.

Cotton soakedin concentratedNH3 (aq)

Cotton soakedin concentratedHCl (aq)NH4 Cl forms


Practice Questions

IGCSE Chemistry6

Multiple choice questions

1. When steam condenses to water at 25 oC, what happens to the water molecules?

(A) They move faster and come close together.

(B) They move faster and move further apart.

(C) They move slower and come close together.

(D) They move slower and move further apart. ( )

2. Which of the following is a correct description of the particles in a liquid?

(A) Particles are arranged in a regular arrangement.

(B) Particles can move past one another due to the weak attractive forces.

(C) Particles vibrate in fixed in positions.

(D) Particles can move around freely in all directions and can be compressed. ( )

3. The following diagrams show some particles in different arrangements.

Which of the following is a correct description of the above diagrams?

I II III

(A) Solid Liquid Gas

(B) Gas Solid Liquid(C) Gas Liquid Solid(D) Solid Gas Liquid ( )

4. In a sample of air at 25 °C, the molecules of oxygen, nitrogen and carbon dioxide move at different average speeds. Which of the following lists the molecules in order of decreasing average speed?

Fastest Slowest

(A) Carbon dioxide Oxygen Nitrogen(B) Nitrogen Carbon dioxide Oxygen(C) Nitrogen Oxygen Carbon dioxide(D) Oxygen Carbon dioxide Nitrogen ( )

I II III


The Particulate Nature of Matter | Practice7

5. Which of the following state change gives out heat to the surroundings?

(A) ice water (B) ice steam

(C) steam ice (D) water steam ( )

6. Which of the following describes the change in state when dry ice is heated?

(A) Evaporation (B) Sublimation

(C) Melting (D) Boiling ( )

7. Which of the following best explains why a hot air balloon rises?

(A) The gas particles in the balloon expand at high temperature and occupy a greater volume, resulting in a decrease in the density of the gas.

(B) The gas particles in the balloon gain energy and move further apart, resulting in a decrease in the density of the gas.

(C) The amount of gas particles in the balloon decreases, resulting in a decrease in the mass of the gas.

(D) The gas particles expand and come closer together as they gain kinetic energy, resulting in a decrease in the density of the gas. ( )

8. The diagrams show the arrangement of particles of substance W at -120 °C and 60 °C.

Which of the following shows the melting and boiling point of substance W?

Melting Point °C Boiling point °C(A) -160 -90(B) -80 80(C) -100 -10(D) -130 20 ( )

9. Which of the factors affect the rate of diffusion?

(A) State of the matter

(B) Temperature

(C) Molecular Mass

(D) All of the above ( )

−120 °C 60 °C


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10. The diagram below shows the cooling curve as water is cooled from 90 °C to −5 °C.

Which of the following shows the correct states of water at V, W, X and Y?

V W to X Y

(A) Liquid Liquid Solid(B) Gas Liquid Solid(C) Gas Liquid and solid Solid(D) Liquid Liquid and solid Solid ( )

11. Which statement is correct about the movement or arrangement of the molecules of this substance?

(A) They move randomly in the solid state.

(B) They move randomly in the liquid state.

(C) They are arranged in fixed positions in the liquid state.

(D) They are not moving in the solid state. ( )

12. Some liquid hexane, C6H14, was poured into a conical flask and it was sealed with a glass stopper. The diagram shows the flask after a few minutes.

What processes are occurring in the flask?

(A) Boiling and condensing

(B) Condensing and evaporating

(C) Evaporating and freezing

(D) Freezing and melting ( )

Temperature/°C

90

−5

V

W X

Y

Time/min

solid liquid

Liquidhexane



13. Which of these changes takes place when solid napthalene (moth balls) is heated?

(A) Crystallisation

(B) Evaporation

(C) Melting

(D) Sublimation ( )

14. Which process occurs as sugar cubes dissolve in warm water to form a solution?

(A) Diffusion

(B) Crystallisation

(C) Evaporation

(D) Melting ( )

15. Gases are highly compressible due to ________________.

(A) the indefinite shape of the gas

(B) the random collision of gas particles

(C) the high kinetic energy of the gas particles

(D) the larger distance between the gas particles ( )

Structured Questions

1. (a) A pure substance X melts at 20 °C and boils at 125 °C, sketch a heating curve to show the conversion of substance X from solid to gaseous state. Label the processes melting and boiling in your sketch.

(b) When substance X boils, the temperature remains constant at 125 oC for a few minutes then rises. Explain this observation.

_______________________________________________________________________________________

_______________________________________________________________________________________

_______________________________________________________________________________________

Temperature/°C

Time/s0


IGCSE Chemistry10

2. Study the table of melting points and boiling points of some compounds:

Sulfur dioxide

AmmoniaHydrogen peroxide

Hydrogen sulfide

Water

Melting Point °C

-73 -77 2 -86 0

Boiling Point °C

-10 -33 150 -60 100

(a) Which of these substances are liquids at room temperature?

_______________________________________________________________________________________

(b) What is the state of sulfur dioxide at room temperature?

_______________________________________________________________________________________

(c) In the space below, sketch the arrangement of the particles of ammonia and hydrogen peroxide at 0 °C.

Ammonia Hydrogen peroxide

3. Given the relative molecular mass of oxygen gas is 32 and nitrogen is 28. Predict and explain what will happen to the water level, X when the beaker is filled with nitrogen gas.

__________________________________________________________________________________________

__________________________________________________________________________________________

beaker

porous pot

oxygen

X

water



4. (a) A student placed a copper(II) sulfate crystal into a beaker of water at room temperature. After 10 minute, a dense blue colour was observed in the water at the bottom of the beaker. After 2 hours, the copper(II) sulfate crystal dissolves and the water appears light blue. Explain the observations using the Kinetic Particle Theory.

_______________________________________________________________________________________

_______________________________________________________________________________________

_______________________________________________________________________________________

(b) The student placed another copper(II) sulfate crystal into a beaker of warm water at 50 °C. It took only 1 hour for the beaker of water to turn light blue. Account for the difference in the time taken.

_______________________________________________________________________________________

_______________________________________________________________________________________

_______________________________________________________________________________________

5. (a) Iris was observing the movement of some smoke particles under a microscope. In the box below, sketch the movement of a smoke particle.

(b) Explain the movement of the smoke particle.

_______________________________________________________________________________________

_______________________________________________________________________________________


Contents · State the properties of solids, liquids and gases. ... As the mass of the particles...

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Transcript of Contents · State the properties of solids, liquids and gases. ... As the mass of the particles...