Concept of Matter PDF

MODULE THREE CONCEPT OF MATTER Akoshile C.O1. and Abdus-Salam, N2 1Department of Physics, University of Ilorin 2Department of Chemistry, University of Ilorin Introduc...

MODULE THREE CONCEPT OF MATTER Akoshile C.O1. and Abdus-Salam, N2 1Department of Physics, University of Ilorin 2Department of Chemistry, University of Ilorin Introduction This chapter discusses the concept of matter. Often one keeps in the mind what he thinks matter is. It does not imply universal definition. Concept is like an accepted norm or definition. So, while trying to understand matter, the adopted concept is what is perceived and accepted as matter. Interestingly, only two kinds of matter exist in the world. Learning Outcomes At the end of this module, you should be able to: (i) define matter (ii) describe the scientific methods of studying matter. (iii) classify matter based on its composition and physical states (iv) explain the kinetic theory of matter (v) define what an atom is and explain properties of the 3 sub atomic particles (vi) explain the significance of Nuclear change Main Body Introduction The module introduces you into the concept of matter vis-a-vis the Kinetic Theory, States of Matter and Nuclear Threats. This module is divided into three units as follows: Unit 1: Definition of Matter Unit 2: Change of State of Matter Unit 3: Nuclear Change Unit 1: Definition of Matter Contents 1.0 Introduction 2.0 Learning Outcomes 3.0 Main Contents 3.1 What is Matter? 3.2 The Kinetic theory of Matter 4.0 Summary 5.0 Self-Assessment Questions (SAQs) 6.0 Tutor Marked Assignments (TMAs) 7.0 Further Reading 1.0 Introduction Often one keeps in the mind what he thinks matter is. It does not imply universal definition. Concept is like an accepted norm or definition. So, while trying to understand matter, the adopted concept is what is perceived and accepted as matter. Interestingly, only two kinds of matter exist in the world. 2.0 Learning Outcomes At the end of this unit, you should be able to: (i) define matter (ii) describe the scientific methods of studying matter. (iii) classify matter based on its composition and physical states (iv) explain the kinetic theory of matter 3.0 Main Contents 3.1 What is Matter? The simplified definition of matter is anything that occupies space, possesses mass of its own, offers resistance to change of inertia and may be felt by any of our sensory organs. Matter exists as a living and non-living entity. Living matter has the properties of respiration, growth, movement, metabolism (eating and excretion) and reproduction. Non-living matter does not exhibit the above properties. Growth in non-living matter only comes if there is an addition of the same or different matter by some processes to the matter. Matter is constituted. This means that matter is also made up of something else. Matter by its composition can be divided into: Pure substances and Mixtures. Matter can also exist in any of the three physical states which are solid, liquid, gas or plasma.  Fig. 1: Classification of Matter Matter can be represented pictorially while a theory is a statement of facts for understanding, explaining and making predictions about an observable phenomenon. It is used as a plausible general principle to explain a phenomenon. A scientific law is a statement of fact that has been subjected to critical analysis, experimentation and found to correctly explain an observable phenomenon under condition(s) stated. An element has only one type of atom e.g. hydrogen. About 118 elements exist in nature and are arranged into eight (8) periods of the periodic table. These elements are found naturally in one of the three physical states of matter for example (mercury, bromine as liquid; sodium, copper as solid and hydrogen, oxygen as gas. A compound has more than one type of atom bonded together chemically which can only be separated by a chemical process e.g. H2O is made up of hydrogen and oxygen. A mixture however is made up of more than one element or compound in a weak bond that requires no chemical process to separate, but requires only a simple physical procedure. For example a class of boys and girls is a mixture that can be separated by simple instruction of “boys, sit down” and “girls, stand up”. When matter exists as a mixture, it could be homogeneous such as a solution (e.g. salt in water) or air mixture (e.g. mixture of N2, O2, CO2, H2O) or heterogeneous mixture such as chocolate or soil.  Fig. 2: The Periodic table of elements Attempt to develop the concept of matter involves many propositions and developing hypothesis. From such hypothesis, theory of matter emerges. The first step is to know the properties of matter. 3.2 The Kinetic theory of Matter The word kinetic stands for motion while a theory is a statement of facts for understanding, explaining and making predictions about an observable phenomenon. It is used as a plausible general principle to explain a phenomenon. The Greeks in the early stages of formulation of the kinetic theory conceptualized that if attempt is made to continually subdivide matter, a smallest one will be attained that can exist on its own. This is discrete, that is, it is a repeatable entity, cannot be continuously fractionalized at will. This entity is called molecule and it is made up of one or more atoms. This means we can explain the behaviour of matter by understanding its state or motional behaviour (kinetics) The particles of solids only vibrate and rotate about a mean position. Particles of liquids vibrate and rotate about a mean position but can also easily slide over each other. Particles of gas move randomly and are translated from one place to another. In building up the kinetic theory, some fundamental assumptions are made and employed. They are: (1). Particle dimension is much less than the distance between collisions. (2). Particle velocity is large such that there are many collisions occurring in a short time interval. (3). Separation between particles is large such that mutual columbic (charged particle) forces of attraction or repulsion are negligible. (4). Collisions between particles are perfectly elastic. (5). Particles have no sense of history between collision. (6). Motion is random. 4.0 Summary Matter is anything that occupies space and possesses mass of its own. Matter can also exist in any of the three physical states which are solid, liquid, gas or plasma. The behaviour of matter can be explained by understanding its state or motional behaviour (Kinetic Theory). 5.0 Self-Assessment Questions (SAQs) i. Define matter. ii. Describe the scientific methods of studying matter. iii. Classify matter based on its composition and physical states iv. List the assumptions of the Kinetic theory of matter. 6.0 Tutor Marked Assignments (TMAs). Use an appropriate chart to classify matter based on composition.. Differentiate between the kinetics of the three states of matter. Define the following terms: i. Elements ii. Compounds iii. Mixtures 7.0 Further Reading Cutnell, J.D. and Johnson, K.W. (1989) Physics, John Wiley and Sons, NY Unit 2: Change of State of Matter Contents 1.0 Introduction 2.0 Learning Outcomes 3.0 Main Contents 3.1 States of Matter 3.2 Changes in State of Matter 3.3 Subatomic Particles 4.0 Summary 5.0 Self-Assessment Questions (SAQs) 6.0 Tutor Marked Assignments (TMAs) 7.0 Further Reading 1.0 Introduction Matter is able to transform from one physical state to another. The state in which matter exists at a given time depends on how closely held its particles are. There are three state of matter which are solid, liquid and gas or plasma. The subatomic particles of atoms are also explained. 2.0 Learning Outcomes At the end of this unit, you should be able to: (i) describe the three states of matter (ii) explain the temperature dependence on state (iii) list the subatomic particles of an atom 3.0 Main Contents 3.1 States of Matter Matter can exist in any of the three physical states which are solid, liquid, gas or plasma. Matter takes its own shape when in solid form. It takes the shape of the container when in liquid (and flows when poured) and occupies all available spaces as gas or plasma. The state of matter is distinguishable by the temperature and appearance of the matter. 3.2 Changes in State of Matter Matter is capable of change from one physical state to another due to temperature change experienced by the matter. The change may involve transformation of form when a chemical reaction is involved. The former is referred to as physical change and the latter as chemical change. The nature of matter obtained when a chemical change occurs is fundamentally different from the starting matter. For example, when an iron bar is exposed to the right humidity, temperature and air, it rusts. The product of rust is different from the pure iron bar. All physical change involves change of state. Many a time, matter changes from solid to liquid and to gas but in few others, it changes from solid to gas without passing through liquid state. Such substances are said to sublime and the process of change is sublimation. Examples include iodine and ammonium chloride. Figure 1: Temperature dependence on the state of matter 3.3 Subatomic Particles Beyond the atomic study are the subatomic particles revealed by probes made using x-rays. Atomic models were constructed by Rutherford and Bohr. The model showed that the atom had a small positively charged nucleus surrounded by electrons. Hydrogen is the smallest atom having nuclear particle of one proton and an electron moving round it in spherical orbit as shown fig.2 Figure 2: The planetary model of atom More complicated nucleons have electrons moving in elliptical orbits. The nucleus contains protons and neutrons with the following properties, Particle Symbol Charge Mass Proton p positive (+1) 1.673 x 10-27kg Neutron n neutral (0) 1.675 x 10-27kg Electron e negative (-1) 9.1 x 10-31kg where charge of 1e = 1.602 X 10-19 Coulombs A neutral atom always has equal number of protons and electrons since the neutron has no charge. Positive and negative charges (positive-negative or negative-positive) attract each other while two similar charges (positive-positive or negative-negative) repel each other. 4.0 Summary Matter can exist in any of the three physical states which are solid, liquid, gas or plasma. Matter is capable of change from one physical state to another due to temperature change experienced by the matter. The subatomic particles are protons, electrons and neutrons. 5.0 Self-Assessment Questions (SAQs) i. State the three states of matter. ii. What are the transformation processes between the states of matter. iii. List the 3 subatomic particles with their symbols and charges. 6.0 Tutor Marked Assignments (TMAs) 1. What is sublimation? Give two types of substances that sublime. 2. Define condensation. 3. Differentiate between a physical and chemical change in state. 7.0 Further Reading Halliday, D. And Resnick, R.,(1981) Fundamentals of Physics. John Wiley and Sons. NY Unit 3: Nuclear Change Contents 1.0 Introduction 2.0 Learning Outcomes 3.0 Main Contents 3.1 Nuclear Change 3.2 Mass defect 3.3 Threats and Implications of Nuclear War 4.0 Summary 5.0 Self-Assessment Questions (SAQs) 6.0 Tutor Marked Assignments (TMAs) 7.0 Further Reading 1.0 Introduction The nucleus of the atom is very vital to the composition and properties of an atom and a lot of processes and application arises from this particle. 2.0 Learning Outcomes At the end of this unit, you should be able to: (i) describe the changes that occur in the nucleus (ii) explain a mass defect (iii) understand the threats and implications of nuclear war 3.0 Main Contents 3.1 Nuclear Change A nuclear change is one involving either fission (splitting) of the nucleus of an atom, or fusion (combining) of neutrons and protons to form heavier atoms. It involves about 1,000,000 times as much energy as a chemical change. Some elements are observed to undergo nuclear change. These elements are said to be radioactive e.g. uranium. They emit radiation which can be split using magnetic or electric field as shown in Figure 1. An example of this reaction that leads to the emission of alpha particle is: 226 222 4 88 Ra 86 Rn + 2 He + radiation Other types of radiations are X-rays. Both alpha and beta particles are deflected by magnetic and electric plates (field) where alpha particle is Helium nucleus and beta particles are electrons. Examples of other nuclear reactions are: The above are called nuclear reactions. A A nuclear particle is represented as: Z XN where A is the mass number, Z is the proton number, and N is the neutron number. Nuclear reactions are divided into two types: Nuclear Fusion which is bonding together of two or more nuclei Nuclear fission is division of a nucleus into two or more smaller nuclei 3.2 Mass defect during nuclear change During nuclear reaction, mass defect Δm is observed. Δm is the difference in mass between the mass of the product and the reactants. This seems to imply violation of the law of conservation of mass. This law has been restated as the law of conservation of energy when Albert Einstein showed that the change in mass turned into energy, obeying the Einstein law: E = Δmc2 Mass defect Δm is calculated from the knowledge of values of the mass of protons, neutrons, electrons, etc. A nucleus N has mass ZMH+ since it contains Z protons and (A-Z) Mn for (A-Z) neutrons and the addition of these two masses when subtracted from the mass of is found not to be equal to zero. It gives mass defect Δm i.e. in its formation from constituent particles; the product has mass defect Δm. Δm = ZMH + (A-Z) Mn - MA This change in mass then shows up as energy. So the mass and energy become synonymous. Mass can change into energy and vice versa. This energy is observed in other nuclear reactions such as fission or fusion and is about 200 Mega - electron volts (200 MeV) 3.3 Threats and Implications of Nuclear War The energy released during nuclear reactions is enormous. It is of the order of mega-electron volts or millions of electron volts (MeV). The magnitude of the energy produced in a nuclear reaction by 1g of uranium nuclear fuel is 1/235 x 6.02 x 1023 x 133 200MeV = 68100 x 109GJ. What makes it of special concern is that this enormous amount of energy is released in a short time on a small piece of land - area producing tremor with tremendous impact over long range. When such a war is becoming feasible, it is considered a threat. If it eventually happens; it is then a nuclear war and the consequence(s) is/are regarded as the implication(s) of such war. It is important therefore to understand the nuclear energy involved. Chain reaction Chain reaction occurs when proceed of one reaction leads to another with both source and product initiating the next reaction and resulting in an avalanche. This result in multiples of the energy produced per step and in a very short time large amount of energy is released. This large amount of energy is released in a very short time to a very small volume of space resulting in an explosion or a bomb. In 1944, during World War II, Hiroshima and Nagasaki in Japan were bombed using hydrogen bomb in which 150,000 lives were lost in that test or drop. World War II quickly wound up within a year of its drop. Besides those who died instantly, many who suffered from the dust, clay or even after- shock either died, became cancerous, disabled or deformed and so on. Its other effects which include psychological disorder linger on for many years. This scenario is well depicted in the film “The Day After”. In 1946, the United States of America Congress passed the Atomic Energy Act. In the same year following agitations to have arms control and disarmament including right to acquire Nuclear Free Zone, the “Nuclear Non-Proliferation Treaty” was signed in the League of Nations that transformed into the United Nations. The intention was not to ever have to use this weapon of mass destruction. Signing of this treaty was made voluntary. Those who had the capability to develop nuclear warheads first constituted themselves into superpowers with veto power in the Security Council of the United Nations 4.0 Summary The magnitude of the energy produced in a nuclear reaction has been shown to be very large. This large amount of energy is released in a very short time to a very small volume of space resulting in an explosion or a bomb. The fission reaction energy can be trapped as heat energy and the heat energy can then be converted to electrical energy which is a positive use. But its use in warfare can be very catastrophic. Treaties are also being formulated to keep space free and to free other planets from nuclear pollution. 5.0 Self-Assessment Questions (SAQs) i. What is a nuclear change? ii. Define chain reaction. iii. Describe a mass defect. iv. List 3 implications of nuclear threats. 6.0 Tutor Marked Assignments (TMAs) 1. Differentiate between Nuclear fission and fusion 2. What do you understand by the Nuclear Non-Proliferation Treaty.  3. List 3 applications of nuclear technology. 7.0 Further Reading Marion, J.B. And Hornyak, W.F.,(1982) Physics for Science and Engineering. Part 1, CBS College Publishing, NY, USA. Tyder, F (1974) A Laboratory Manual of Physics, Fourth Edition, Edward Arnold (publishers) Lid, London.