We think you have liked this presentation. If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Thank you!
Presentation is loading. Please wait.
Published byAmy Hargrove
Modified about 1 year ago
1 of 35© Boardworks Ltd 2009
2 of 35© Boardworks Ltd 2009
3 of 35© Boardworks Ltd 2009 What is collision theory? Collision theory states that for a reaction to occur: particles must collide with the correct orientation. particles must have sufficient energy particles must collide Most collisions do not result in reaction because they do not meet the second and third criteria.
4 of 35© Boardworks Ltd 2009 Activation energy
5 of 35© Boardworks Ltd 2009 Effect of surface area on collisions Only the particles on the surface of a solid will collide with particles of the other reactant. Surface area can be increased by decreasing the size of the reactant particles. Powders have a very large surface area. increasing surface area If the surface area is increased, more particles will be on the surface and able to collide with particles of the other reactant. This means that there will be more collisions in total and therefore more reactive collisions.
6 of 35© Boardworks Ltd 2009 Reaction of marble chips with acid The effect of changing surface area on the rate of reaction can be explored by reacting marble (calcium carbonate) chips and an acid such as 2 mol dm -3 hydrochloric acid. CaCO 3(s) + 2HCl (aq) CaCl 2(s) + CO 2(g) + H 2 O (l) The carbon dioxide gas evolved can be collected and its volume measured over time. The rate at which it is produced is a measure of the rate of reaction. By repeating the experiment with marble chips of different sizes, the effect of surface area on the rate of reaction can be examined.
7 of 35© Boardworks Ltd 2009 Effect of surface area on rate: graph
8 of 35© Boardworks Ltd 2009 Effect of concentration on rate
9 of 35© Boardworks Ltd 2009 Effect of concentration on rate: graph
10 of 35© Boardworks Ltd 2009 Effect of gas pressure on rate
11 of 35© Boardworks Ltd 2009 Effect of pressure on rate: graph
12 of 35© Boardworks Ltd 2009 Effect of temperature on particles
13 of 35© Boardworks Ltd 2009 Effect of temperature on rate Increasing the temperature of the reaction mixture increases the rate of reaction in the following two ways: 1. At higher temperatures, the particles are moving faster, so collide more frequently. A higher number of collisions in total means a higher number of successful collisions. 2. At higher temperatures, a higher proportion of the molecules have the activation energy or more. This means that a higher proportion of collisions is successful.
14 of 35© Boardworks Ltd 2009 Effect of temperature on rate: graph
15 of 35© Boardworks Ltd 2009 Collision theory summary
16 of 35© Boardworks Ltd 2009 Rate of reaction summary
17 of 35© Boardworks Ltd 2009
18 of 35© Boardworks Ltd 2009 Distribution of particle speeds
19 of 35© Boardworks Ltd 2009 Energy distribution curves
20 of 35© Boardworks Ltd 2009 The effect of changing temperature
21 of 35© Boardworks Ltd 2009 Small temperature changes The Maxwell–Boltzmann distribution shows that for a small increase in temperature, there is a relatively large increase in the number of particles with at least the activation energy. A small increase in temperature therefore leads to a large increase in rate. The increase in collision frequency is also a factor, but its effect is small compared to the increase in energy. no. of particles energy EaEa no. particles with E a almost doubled
22 of 35© Boardworks Ltd 2009 Effect of temperature summary
23 of 35© Boardworks Ltd 2009
24 of 35© Boardworks Ltd 2009 Effect of catalysts on rate: graph
25 of 35© Boardworks Ltd 2009 What do catalysts do?
26 of 35© Boardworks Ltd 2009 How do catalysts work? An example is the oxidation of sulfur dioxide: SO 2(g) + V 2 O 5(s) SO 3(g) + V 2 O 4(s) The catalyst is re-formed by reacting with oxygen: V 2 O 4(s) + ½O 2(g) V 2 O 5(s) SO 2(g) + ½O 2(g) SO 3(g) This is catalyzed by vanadium(V) oxide: Catalysts increase the rate of reactions without being used up during the reaction. One way in which this occurs is for the catalyst to be changed during the reaction, then changed back in a second reaction with one of the reactants or products. This is an alternative reaction pathway.
27 of 35© Boardworks Ltd 2009 Catalysts and energy distribution curves
28 of 35© Boardworks Ltd 2009 Heterogeneous catalysts There are two types of catalysts: heterogeneous and homogeneous. Heterogeneous catalysts are in a different phase to the reactants. The catalyst is usually a solid and the reactants are liquids or gases (e.g. solid catalysts for gas reactions in catalytic converters). Industrial examples of heterogeneous catalysis include the iron catalyst used in ammonia production and the Ziegler–Natta catalyst used in poly(e)thene production.
29 of 35© Boardworks Ltd 2009 Homogeneous catalysts Homogeneous catalysts are in the same phase as the reactants. The catalyst and the reactants are usually liquids, such as the hardener added to fibreglass resin. Another example of homogeneous catalysis is the destruction of atmospheric ozone catalyzed by chlorine free radicals. In this reaction the catalyst and reactants are in the gas phase.
30 of 35© Boardworks Ltd 2009 Advantages of catalysts Using a catalyst means that a reaction can take place at the same rate as the uncatalyzed reaction, but at a lower temperature and/or pressure. This has the following advantages, which are particularly important in industry: A non-industrial example is enzyme catalysis in biological washing powders, allowing efficient washing at a lower temperature. lower energy demands… …therefore less CO 2 produced… …therefore less environmental impact… …and lower production costs.
31 of 35© Boardworks Ltd 2009 Catalysts: true or false?
32 of 35© Boardworks Ltd 2009
33 of 35© Boardworks Ltd 2009 Glossary
34 of 35© Boardworks Ltd 2009 What’s the keyword?
35 of 35© Boardworks Ltd 2009 Multiple-choice quiz
1 of 39© Boardworks Ltd 2007 Kinetics. © Boardworks Ltd of 39.
Rates & Extents of Reactions. Rates & Extents of Rates & Extents of Reactions Quiz A Quiz A What prevents reaction from What prevents reaction from going?
RATES OF REACTION A guide for GCSE students 2010 SPECIFICATIONS KNOCKHARDY PUBLISHING.
BL TIER 3 TIER 3 Identify suitable experimental procedures for measuring rates of reactions Identify the factors affecting the rate of a reaction Calculate.
RATES OF REACTION - 1 A guide for A level students KNOCKHARDY PUBLISHING.
Types of reactions. What is a Chemical Reaction? A chemical reaction is the process by which one or more substances change into one or more new substances.
Topic 21 Topic 21 Topic 21: Reaction Rates Table of Contents Basic Concepts Additional Concepts Topic 21 Topic 21.
William L Masterton Cecile N. Hurley Edward J. Neth University of Connecticut Chapter 11 Rate of Reaction.
© Nuffield Foundation 2013 Practical Work for Learning The effect of concentration on the rate of a reaction.
Kinetics (Reaction Rate) How Fast Does the Reaction Go.
NATIONAL 4/5 CHEMISTRY CHEMICAL CHANGES AND STRUCTURE LESSON 1 REVISION OF FACTORS THAT SPEED UP A REACTION.
Chemical Kinetics Is a study of how fast chemical reactions occur.
© Boardworks Ltd of of 39© Boardworks Ltd 2007 Irreversible reactions Most chemical reactions are considered irreversible – the products that.
CATALYSIS A guide for A level students KNOCKHARDY PUBLISHING.
Kinetics. Reaction rates Concerned with why some reactions are fast and others are slow. A reaction rate is quantitatively written as either: Change in.
Kinetics The study of reaction rates. Spontaneous reactions are reactions that will happen - but we cant tell how fast. Diamond will spontaneously turn.
I. Rates of Reaction Ch. 16 – Reaction Energy and Reaction Kinetics.
Reaction Rates and Equilibrium M.Elizabeth Collision Theory Used to Explain Reaction Rates Atoms, ions, and molecules can form a chemical bond when.
Chapter 17 - Chemical Kinetics Mr Nelson. Kinetics Studies the rate at which a chemical process occurs. Besides information about the speed at which reactions.
Term Test 2 Click Here. This presentation is completely interactive In order for this presentation to work you MUST follow the indicated tabs on each.
Chemical Kinetics Chapter 13. Chemical Kinetics Thermodynamics – does a reaction take place? Kinetics – how fast does a reaction proceed? Reaction rate.
Chapter 17 and 18 Reaction Rates and Equilibrium Pre-AP Chemistry BMHS Anahit Pivazyan Activation Energy is being supplied Activated Complex.
Chemical Kinetics The area of chemistry that concerns reaction rates and reaction mechanisms.
Le Chatelier’s Principle AP Chemistry. Le Chatelier’s Principle If a stress is applied to a system at equilibrium, the system will change to relieve that.
Reaction Rates and Equilibrium Chapter 18. Essential Question: How is the rate of a chemical change expressed, and what four factors influence the rate.
Reaction Rate How Fast Does the Reaction Go?. Collision Theory l In order to react molecules and atoms must touch each other. l They must hit each other.
Section Alkanes know that alkanes are saturated hydrocarbons know that petroleum is a mixture consisting mainly of alkane hydrocarbons understand.
Equilibrium. Non reversible reactions Some chemical and physical reactions occur until one or all the reactants are used up Example 1 Evaporation of water.
Gas Density: Summary The molar concentrations and densities of gases increase as they are compressed (less volume, right?), but decrease as they are heated.
Chapter 5 Chemical Reactions. Chemical Reaction Another name for a chemical change Another name for a chemical change New properties when you are done.
© 2016 SlidePlayer.com Inc. All rights reserved.