Chemical Change & Rate Of Reaction

邊玩邊學

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Physical & Chemical Changes

Physical changes do not produce new substances; they are often easy to reverse (e.g., melting, dissolving).
Chemical changes form new substances with different properties; signs include colour change, temperature change, effervescence.
Example of colour change: copper (orange-brown) + silver nitrate → silver solid + blue solution.
Temperature changes: exothermic reactions release heat (e.g., CaO + water); endothermic reactions absorb heat (e.g., dissolving ammonium chloride).
Effervescence (fizzing) indicates gas production, e.g., alkali metals + water produce hydrogen.

The metal displacement reaction of silver and copper

Rates of Reaction Factors

Rate of reaction is affected by: concentration (or pressure for gases), surface area of solids, temperature, and catalysts.
Higher concentration/pressure → more particles per volume → steeper initial gradient, same final product amount.
Higher surface area (e.g., powder vs lumps) → more exposed particles → steeper initial gradient, same final product.
Higher temperature → particles have more kinetic energy → steeper initial gradient, same final product.
Catalysts speed up reaction without being consumed; they provide an alternative pathway with lower activation energy.

Graph showing the effect of concentration on rate of reaction

Collision Theory (Extended)

For a reaction to occur, particles must collide with sufficient energy (≥ activation energy) and correct orientation.
Successful collisions lead to product formation; unsuccessful collisions result in particles bouncing off unchanged.
Rate depends on: number of particles per unit volume, collision frequency, kinetic energy of particles, and activation energy.
Increasing any factor that raises collision frequency or energy increases the number of successful collisions per second.

A successful collision

Explaining Rates Using Collision Theory (Extended)

Concentration: more particles per volume → more collisions per second → higher rate.
Pressure (gases): same particles in smaller volume → more collisions per second → higher rate.
Surface area: more exposed particles → more collisions per second → higher rate.
Temperature: particles gain kinetic energy → more collisions and a greater proportion exceed activation energy → rate increases sharply (≈ doubles per 10 °C).
Catalysts: lower activation energy → more collisions have sufficient energy → higher rate.

Diagram showing the effect of increasing concentration

Investigating the Rate of a Reaction

Common methods: mass loss on a balance, gas volume (downward displacement or gas syringe), disappearing cross (precipitate formation).
Disappearing cross: measure time for a cross to become obscured by sulfur precipitate from sodium thiosulfate + HCl.
Gas collection: e.g., magnesium + acid → hydrogen; measure volume over time.
Catalyst investigation: e.g., hydrogen peroxide decomposition with MnO₂ catalyst; compare gas volumes.
Advantages/disadvantages: mass loss is simple but unsuitable for low‑mass gases; gas syringes are accurate but fragile.

Diagram showing the apparatus needed to investigate the effect of concentration on the rate of reaction

Interpreting Data

Rate is fastest at the start (steepest gradient) because reactant concentration is highest.
As reaction proceeds, gradient decreases; when one reactant is used up, the line becomes horizontal (rate = 0).
To find rate at a specific time, draw a tangent to the curve and calculate gradient = change in y / change in x.
Comparing experiments: higher concentration, temperature, surface area, or catalyst gives a steeper initial curve and same final product amount (if limiting reactant unchanged).
If the amount of limiting reactant is increased, the final product amount increases.

Calculating the rate of reaction from a tangent

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1.Which of the following processes represents a physical change?
Easy
- AAcid base neutralisation
- BMetal displacement reactions
- CBoiling ethanol
- DCombustion of magnesium
2.Physical and chemical changes are different processes. Which of the following rows correctly identifies characteristics of each one?
Easy
- Achemical change - no new substance formed; physical change - change of state
- Bchemical change - no new substance formed; physical change - involves electron transfer
- Cchemical change - new substance formed; physical change - involves electron transfer
- Dchemical change - new substance formed; physical change - change of state
3.Which process is a physical change?
Easy
- Acracking of an alkane
- Bhydration of ethene
- Cfractional distillation of petroleum
- Dthermal decomposition of calcium carbonate
4.The rate of a reaction was monitored by recording the volume of gas produced every 5 seconds. What is the mean rate of reaction in the first 10 seconds of the reaction, in cm³/s? (Data: at 0 s, 0 cm³; at 5 s, 15 cm³; at 10 s, 35 cm³)
Medium
- A2.9
- B3.0
- C3.5
- D2.5
5.A student was investigating the rate of reaction between iron and a solution of sulfuric acid. Two experiments were performed, P and Q, in which the volume of hydrogen produced was recorded at regular intervals. In Experiment P, the volume of gas rose more steeply at the start and reached a higher final volume than in Experiment Q. Which change could explain the difference in results between P and Q?
Medium
- AThe student added a catalyst in P.
- BLarger pieces of iron were used in P.
- CLess concentrated acid was used in P.
- DLarger quantities of both reactants are used in P.
6.A student investigates the rate of reaction between aqueous sodium thiosulphate and aqueous hydrochloric acid by measuring the time taken for a precipitate to obscure a cross underneath the beaker. Which statement is correct for the reaction?
Medium
- AThe precipitate will be formed faster if ice is placed in contact with the beaker.
- BThe precipitate will be formed faster if 10.0 cm³ of water are added to the aqueous sodium thiosulphate.
- CThe precipitate will be formed slower if a catalyst is added to the reaction mixture.
- DThe precipitate will be formed faster if drops of concentrated hydrochloric acid are added to the reaction mixture.
7.A student investigates the effect of temperature on the rate of a reaction. In Experiment 1, the reaction is performed at 10°C. In Experiment 2, the reaction is repeated at 20°C. All other conditions stay the same. Which description matches the results for the volume of gas produced against time?
Medium
- AGraph A: both curves identical
- BGraph B: 20°C curve has steeper slope and higher final volume
- CGraph C: 20°C curve has steeper slope and same final volume, levels off earlier
- DGraph D: 20°C curve has less steep slope and lower final volume
8.Magnesium metal reacts with an excess of hydrochloric acid solution to form magnesium chloride and hydrogen: Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g). Which of the following will not increase the rate of this reaction?
Medium
- AIncrease the temperature of the acid
- BIncrease the surface area to volume ratio of the pieces of magnesium
- CIncrease the concentration of the hydrochloric acid
- DIncrease the volume of hydrochloric acid solution used

更多題目

9.Catalysts are often used in chemical reactions. Which letter represents two correct features of catalysts?
Medium
- AFeature 1 - Lower activation energy for the reaction; Feature 2 - More products made in total
- BFeature 1 - Alternative pathway for the reaction is provided; Feature 2 - Not used up over the course of the reaction
- CFeature 1 - Makes industrial processes cheaper; Feature 2 - Metal catalysts are cheap to buy
- DFeature 1 - Reduce the overall energy change of the reaction; Feature 2 - Can be present in biological systems as enzymes
10.A student investigates the rate of reaction between excess calcium carbonate and sulfuric acid. The investigation is carried out twice, as Experiment 1 and Experiment 2, using the same volume and concentration of acid and the same mass of calcium carbonate. In Experiment 2, the curve of gas volume against time has a steeper initial gradient but reaches the same final volume of gas as Experiment 1. Which change explains this difference?
Medium
- AThe temperature was higher in experiment 2.
- BExperiment 2 was allowed more time to react.
- CSame volume of a more concentrated acid was used in experiment 2.
- DMore calcium carbonate was used in experiment 2.
11.Which of the following statements explains how increasing temperature increases the rate of a reaction?
Medium
- AIncreasing the temperature increases the kinetic energy of the particles so there are a smaller number of successful collisions.
- BIncreasing the temperature increases the kinetic energy of the particles so there are a larger number of unsuccessful collisions.
- CIncreasing the temperature decreases the kinetic energy of the particles so there are a larger number of successful collisions.
- DIncreasing the temperature increases the kinetic energy of the particles so there are a larger number of successful collisions.
12.Which of the following statements best describes the activation energy of a reaction?
Easy
- AThe minimum energy released when colliding particles react.
- BThe minimum energy required for particles to react when they collide.
- CThe maximum energy required for particles to react when they collide.
- DThe maximum energy released when colliding particles react.
13.Which of the following is a sign that a chemical change has occurred?
Easy
- AA change of state from solid to liquid
- BDissolving sugar in water
- CEffervescence (fizzing)
- DMaking a mixture of sand and salt
14.Which factor does NOT affect the rate of a chemical reaction?
Easy
- ATemperature
- BConcentration of reactants
- CColour of reactants
- DPresence of a catalyst
15.A student adds 0.2 g of manganese(IV) oxide to 25 cm³ of 0.1 mol/dm³ hydrogen peroxide and measures the volume of oxygen produced. Which change would produce a steeper initial gradient on the volume-time graph?
Medium
- AUsing 0.1 g of manganese(IV) oxide
- BUsing 25 cm³ of 0.2 mol/dm³ hydrogen peroxide
- CUsing 50 cm³ of 0.1 mol/dm³ hydrogen peroxide
- DUsing the same concentration at a lower temperature
16.In an experiment to investigate the effect of surface area on reaction rate, a student uses marble chips (calcium carbonate) and hydrochloric acid. Which setup will produce the fastest initial rate?
Medium
- ALarge marble chips with 1 mol/dm³ HCl at 20°C
- BPowdered marble with 1 mol/dm³ HCl at 20°C
- CLarge marble chips with 2 mol/dm³ HCl at 20°C
- DPowdered marble with 2 mol/dm³ HCl at 20°C
17.Which statement about catalysts is correct?
Easy
- ACatalysts are used up during the reaction.
- BCatalysts increase the activation energy of the reaction.
- CCatalysts provide an alternative reaction pathway with lower activation energy.
- DCatalysts change the products of the reaction.
18.Which of the following statements correctly describes the effect of increasing concentration on the rate of a reaction?
Medium
- AIncreasing the concentration increases the kinetic energy of the particles, resulting in more successful collisions per unit time.
- BIncreasing the concentration increases the rate of reaction as there is more space between particles.
- CIncreasing the concentration increases the rate of reaction as there are more collisions between particles per unit time.
- DIncreasing the concentration increases the rate of reaction as there are more collisions between particles at the beginning of the reaction.
19.Which statement about the effect of increasing pressure on the rate of a gas reaction is correct?
Medium
- AIncreasing pressure increases the kinetic energy of gas particles.
- BIncreasing pressure decreases the volume, so particles collide less frequently.
- CIncreasing pressure forces particles together, increasing the number of collisions per second.
- DIncreasing pressure has no effect on the rate of reaction.
20.The reaction between magnesium and hydrochloric acid produces hydrogen gas. Which apparatus setup is most suitable for measuring the rate of this reaction?
Easy
- AA beaker on a balance measuring mass loss
- BA test tube with a balloon to collect gas
- CA conical flask with a gas syringe
- DA boiling tube with a rubber stopper
21.In the 'disappearing cross' experiment, sodium thiosulphate reacts with hydrochloric acid to form a yellow precipitate of sulfur. Which change would cause the cross to disappear fastest?
Medium
- AUsing a more dilute sodium thiosulphate solution
- BCooling the reaction mixture in an ice bath
- CAdding a catalyst such as manganese(IV) oxide
- DUsing a higher concentration of hydrochloric acid
22.A reaction has an activation energy of 50 kJ/mol. At 25°C, the reaction is slow. Which change would increase the proportion of collisions with energy greater than 50 kJ/mol?
Hard
- AIncreasing the concentration of reactants
- BIncreasing the surface area of a solid reactant
- CIncreasing the temperature to 35°C
- DAdding a catalyst that lowers the activation energy to 40 kJ/mol
23.In an experiment, 0.2 g of manganese(IV) oxide was added to 25 cm³ of 0.1 mol/dm³ hydrogen peroxide. The volume of oxygen produced was recorded every minute. The experiment was repeated with the same mass of catalyst and at the same temperature, but using 25 cm³ of 0.2 mol/dm³ hydrogen peroxide. How does the final volume of oxygen produced in the second experiment compare to that in the first?
Medium
- AIt is the same.
- BIt is half the volume.
- CIt is double the volume.
- DIt is four times the volume.
24.A student measures the rate of reaction between calcium carbonate and hydrochloric acid by monitoring the mass loss of the reaction flask over time. Which gas is being lost from the flask?
Easy
- AHydrogen
- BCarbon dioxide
- COxygen
- DChlorine
25.The graph shows the volume of gas produced against time for a reaction between magnesium and excess hydrochloric acid. Which change would produce a curve with a steeper initial gradient but the same final volume of gas?
Medium
- AUsing a lower concentration of hydrochloric acid
- BUsing a larger piece of magnesium (same mass)
- CUsing powdered magnesium (same mass)
- DIncreasing the volume of hydrochloric acid
26.Which statement about the effect of a catalyst on a reaction is correct?
Easy
- AA catalyst increases the activation energy of the reaction.
- BA catalyst is used up during the reaction.
- CA catalyst provides an alternative pathway with a lower activation energy.
- DA catalyst increases the total amount of product formed.
27.Which of the following is a physical change?
Easy
- ABurning wood
- BRusting of iron
- CMelting ice
- DCooking an egg
28.The rate of a reaction between a metal and an acid is measured by collecting the hydrogen gas produced. Which factor would increase the rate of this reaction?
Easy
- ADecreasing the temperature of the acid
- BUsing larger pieces of the metal (same total mass)
- CDecreasing the concentration of the acid
- DUsing a catalyst
29.A student investigates the reaction between calcium carbonate and hydrochloric acid. The volume of carbon dioxide produced is measured over time. The experiment is repeated using the same mass of calcium carbonate but in powdered form, and the same volume and concentration of acid. Which statement correctly describes the results for the powdered calcium carbonate?
Medium
- AThe initial rate is slower and the final volume of gas is larger.
- BThe initial rate is faster and the final volume of gas is the same.
- CThe initial rate is the same and the final volume of gas is larger.
- DThe initial rate is faster and the final volume of gas is smaller.
30.In the collision theory, what is meant by a 'successful collision'?
Easy
- AA collision where particles bounce off each other without reacting.
- BA collision where the particles have sufficient energy to react and form products.
- CA collision that occurs at a low temperature.
- DA collision that happens very quickly.
31.A reaction has an activation energy of 50 kJ/mol. At 25 °C, the reaction is slow. Which change would increase the proportion of collisions with energy greater than the activation energy?
Medium
- AIncreasing the concentration of reactants
- BIncreasing the pressure of gaseous reactants
- CIncreasing the temperature
- DUsing a catalyst
32.In an experiment to investigate the effect of surface area on reaction rate, a student uses marble chips (calcium carbonate) and hydrochloric acid. Which setup would produce the fastest initial rate of reaction?
Medium
- ALarge marble chips with 1 mol/dm³ acid at 20°C
- BPowdered marble with 1 mol/dm³ acid at 20°C
- CLarge marble chips with 2 mol/dm³ acid at 30°C
- DPowdered marble with 2 mol/dm³ acid at 30°C
33.The rate of a reaction between calcium carbonate and hydrochloric acid is measured by monitoring the mass loss of the reaction flask over time. Which gas is responsible for the mass loss?
Easy
- AHydrogen
- BOxygen
- CCarbon dioxide
- DChlorine
34.Which of the following statements about catalysts is correct?
Easy
- ACatalysts are used up during the reaction
- BCatalysts increase the activation energy of a reaction
- CCatalysts provide an alternative reaction pathway with a lower activation energy
- DCatalysts change the products of a reaction
35.A student investigates the rate of reaction between sodium carbonate granules and dilute hydrochloric acid. The investigation is carried out twice, as Experiment 1 and Experiment 2. The volume of acid, the temperature, and the mass of the sodium carbonate granules are kept the same in both experiments. Which row correctly compares the concentration of the acid (C), the average kinetic energy of the particles (KE), and the rate of reaction (R) in Experiment 2 relative to Experiment 1 if the acid in Experiment 2 is more concentrated?
Hard
- AC higher, KE same, R higher
- BC higher, KE higher, R higher
- CC same, KE higher, R higher
- DC higher, KE same, R same
36.A student measures the rate of reaction between magnesium and hydrochloric acid by collecting hydrogen gas in a gas syringe. After 30 seconds, 60 cm³ of gas have been collected. What is the mean rate of reaction in cm³/s during the first 30 seconds?
Easy
- A0.5 cm³/s
- B2.0 cm³/s
- C30 cm³/s
- D1800 cm³/s
37.In collision theory, what is needed for a collision to be successful?
Easy
- AThe particles must collide with sufficient energy and in the correct orientation
- BThe particles must collide with any energy, regardless of orientation
- CThe particles must have a low kinetic energy to avoid bouncing off
- DThe particles must be in the same state of matter
38.A physical change produces new chemical substances.
Easy
True or false?
39.Which of the following factors does NOT affect the rate of a chemical reaction?
Easy
- ATemperature
- BConcentration
- CColour of reactants
- DSurface area
40.A catalyst increases the rate of reaction by being consumed in the reaction.
Easy
True or false?
41.Which statement about the effect of increasing temperature on reaction rate is correct?
Easy
- AIt decreases the number of collisions
- BIt increases the activation energy
- CIt increases the kinetic energy of particles
- DIt decreases the frequency of successful collisions
42.Match each factor to its effect on reaction rate (increase/decrease).
Easy
- Increase concentration
- Increase surface area
- Add a catalyst
- Increases rate
- Increases rate
- Increases rate
43.Which of the following are correct statements about catalysts? (Select all that apply)
Medium
- ACatalysts are used up in the reaction
- BCatalysts provide an alternative reaction pathway with lower activation energy
- CCatalysts increase the number of successful collisions
- DCatalysts change the products of a reaction
- ECatalysts are specific to certain reactions
44.Arrange the following steps in the correct order to measure the rate of reaction between magnesium and hydrochloric acid by collecting gas.
Easy
- Add magnesium ribbon to the flask
- Connect the flask to a gas syringe
- Start the stopwatch
- Measure the volume of gas at regular intervals
45.Match each factor to the correct effect on the rate of reaction.
Medium
- Increasing temperature
- Increasing concentration
- Adding a catalyst
- Decreasing particle size
- Provides an alternative pathway with lower activation energy
- Increases the frequency of collisions by increasing particle speed
- Increases the frequency of collisions by increasing the number of particles per unit volume
- Increases the surface area exposed to reactants
46.Arrange the following steps in the correct order to measure the rate of reaction between magnesium and hydrochloric acid by collecting hydrogen gas using an inverted measuring cylinder.
Medium
- Add magnesium ribbon to the conical flask and quickly replace the bung
- Fill a measuring cylinder with water and invert it in a water trough
- Connect the delivery tube from the flask to the inverted measuring cylinder
- Measure the volume of gas collected in a fixed time
47.Which of the following statements about collision theory are correct? (Select all that apply)
Medium
- AA successful collision requires particles to collide with sufficient energy
- BIncreasing temperature increases the proportion of collisions with energy greater than the activation energy
- CA catalyst increases the rate of reaction by increasing the number of collisions
- DIncreasing concentration increases the frequency of collisions
- EAll collisions between reactant particles result in a reaction
48.Complete the sentence with the correct term.
Easy
The minimum energy that colliding particles must have to react is called the ____ energy.
49.In an experiment, 0.2 g of manganese(IV) oxide was added to 25 cm³ of 0.1 mol/dm³ hydrogen peroxide. The volume of oxygen produced was recorded. The experiment was repeated using 25 cm³ of 0.2 mol/dm³ hydrogen peroxide. How many times more oxygen is produced in the second experiment?
Easy
50.State one observation that indicates a chemical reaction is taking place when copper is added to silver nitrate solution.
Easy
51.In an experiment, 0.2 g of manganese(IV) oxide is added to 25 cm³ of 0.1 mol/dm³ hydrogen peroxide. The volume of oxygen produced is recorded. The experiment is repeated using 25 cm³ of 0.2 mol/dm³ hydrogen peroxide. Assuming the same conditions, what volume of oxygen (in cm³) will be produced? (The original experiment produced 30 cm³ of oxygen.)
Medium
52.Complete the sentence by filling in the blank.
Easy
A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower ____ energy.
53.Explain why increasing the temperature increases the rate of a chemical reaction. Use collision theory in your answer.
Medium
54.In an experiment, 0.2 g of manganese(IV) oxide was added to 25 cm³ of 0.1 mol/dm³ hydrogen peroxide. The volume of oxygen produced was recorded. The experiment was repeated using 25 cm³ of 0.2 mol/dm³ hydrogen peroxide. How many times more oxygen is produced in the second experiment?
Easy
- A4
- B1
- C3
- D2
55.In an experiment, 0.2 g of manganese(IV) oxide is added to 25 cm³ of 0.1 mol/dm³ hydrogen peroxide. The volume of oxygen produced is recorded. The experiment is repeated using 25 cm³ of 0.2 mol/dm³ hydrogen peroxide. Assuming the same conditions, what volume of oxygen (in cm³) will be produced? (The original experiment produced 30 cm³ of oxygen.)
Medium
- A66 cm³
- B54 cm³
- C60 cm³
- D72 cm³

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