APSC 175 Matter and Energy Properties of Matter D fi iti f M tte n on o a er: Anything that occupies space and displays properties of MASS and INERTIA D fi iti f M tte n on o a er: INERTIA: Tendency for an object to remain at rest or in uniform motion Change will occur if external force is applied MASS: Quantity of matter in an object Wh i t t dy are we n eres e in matter? Curiosity !? M d k l d W d tto ern now e ge: e can ecompose ma er into its smallest components and reassemble these components into materials that do not exist naturally. Example: Petroleum MOTOR FUEL PLASTICS SYNTHETIC FABRICS PESTICIDES PHARMACEUTICALS D fi iti f M tte n on o a er: COMPOSITION OF MATTER R f t ? t ? ? t ? f tte ers o par s or componen s o ma er and their relative proportion PROPERTIES OF MATTER Qualities of matter which can be used to distinguish one sample of matter from others D fi iti f M tte n on o a er: Physical and Chemical Changes PHYSICAL CHANGE Composition remains unchanged! CHEMICAL CHANGE Change in composition Cl ifi ti f M ttass ca on o a er: Cl ifi ti f M ttass ca on o a er: Substance is a single pure form of matter , . Example: water, copper, sugar Mixtures contain two of more substances mixed together . Example: air, steel, soda-pop Mixtures can be: Homogeneous mixtures Heterogeneous mixtures Cl ifi ti f M ttass ca on o a er: Homogeneous and heterogeneous mixtures A solution of salt in water is a homogeneous mixture The sample has a uniform composition throughout Noodle soup is a heterogeneous mixture Materials are not uniformly dispersed over the whole sample So?.., what is matter made up of? ATOMS Atoms are small particles that cannot be made any smaller and still behave like a chemical system So?.., what is matter made up of? All matter consists of atoms. Substance can be made up of one or l t f tsevera ypes o a oms. A substance that is made up of a single, characteristic type of atoms is called an element. Each element has a type of atom different f th f th l trom ose o any o er e emen . Dalton?s Atomic Theory (1808) 1. Each chemical element is composed of minute, indestructible particles called ta oms. 2. All atoms of an element are identical, but different from atoms of other elements . 3. Elements forming compounds always combine in a simple numerical ratio of atoms e.g. 1 atom of A to 2 atoms of B, or 1 atoms of A to 1 atoms of B A new feature: electrons ? Michael Faraday invents the cathode ray tube, 1850?s, generating a negative ray. ? In 1897, JJ Thomson establishes the ray consists of negatively charged particles found in all atoms. ? These are later called ?electrons.? At about the same time ... ? In 1910, Ernest Rutherford reported that atoms were mostly empty . ?[It was] as if you had fired a 15-inch shell at a piece of tissue paper and it came back and hit you.? - Rutherford Rutherford?s explanation (1911) 1. Most of the atomic mass & all of the positive charge were concentrated in a tiny nucleus. 2. The magnitude of positive charge was different for different atoms and was about half the atomic weight. 3. There are equal numbers of electrons outside the l it f itinuc eus as un s o pos ve charge within the nucleus. More particles ... ? Rutherford (1919) discovers the proton ? Chadwick (1932) discovers the neutron PROPERTIES OF MATTER P ti broper es can e: INTENSIVE ? independent of the mass EXTENSIVE ? vary with the mass Mass describes the quantity of matter in an object What is the difference between mass and weight? The object occupies a certain volume Density = Mass Volume PROPERTIES OF MATTER Mass is a base quantity according to SI SI ? Systeme Internationale d?Unite PROPERTIES OF MATTER Units formed as a combination of the seven fundamental units are called DERIVED UNITS Unit for density [kg/m3] is a derived unit HOMEWORK: Find the definition of the following units: 1s ; 1mole; 1A In class we will cover the definition of 1m and 1K PROPERTIES OF MATTER Unit of length is a METRE (Meter) Original definition: 1/10,000,000 of the distance between the Equator and the North Pole (1791) A prototype was built from a metal bar and kept in Paris DIDN?T WORK!!!! ????..WHY? what?s wrong with Paris? PROPERTIES OF MATTER Unit of length is a METRE (Meter) what?s wrong with Paris? Answer: NOTHING??on the contrary!! Correct answer: THE METAL BAR WAS ?TEMPERATURE SENSITIVE? New definition: 1 m is the distance traveled by light in a vacuum / fin 1 299,792,458 o a second PROPERTIES OF MATTER THE METAL BAR WAS ?TEMPERATURE SENSITIVE? WHY? THERMAL EXPANSION Solids expand when heated and contract when cooled PHYSICS OF THERMAL EXPANSION Solids expand when heated and contract when cooled The thermal expansion of solids has its origin in lattice vibrations PHYSICS OF THERMAL EXPANSION The atoms or molecules in the lattice oscillate with a certain amplitude about their equilibrium position The intensity of lattice vibrations increases as the temperature rises The atoms and molecules move farther away in average positions causing an increase in volume of the solids COEFFICIENT OF LINEAR EXPANSION For most solids there is a linear variation of expansion with temperature which can be expressed as: ?L =?L0?T An object of length L0 will be exposed to a change in length ? L when its temperature changes by ?T ? - coefficient of linear expansion FIND UNITS for ? ! ANOMALIES IN THERMAL EXPANSION ABRUPT CHANGES IN VOLUME 1. Polymorphic transformation EXAMPLE: SiO2 2. Change in magnetic properties EXAMPLE All ith ti ti: oys w magne c proper es bellow Curie temperature have low coefficients of thermal expansion PROPERTIES OF MATTER OTHER PROPERTIES OF SOLID MATTER WHICH DEPEND ON LATTICE VIBRATIONS IN A SIMILAR WAY - Electrical resistance - Heat capacity vprodan Microsoft PowerPoint - APSC175 lecture 1 1112.pptx
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