Introduction
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Chemistry is the study of matter and its composition, properties, and the changes it undergoes. There are several key points: 1) Matter is anything that has mass and takes up space, and can be either a pure substance or a mixture. 2) Chemical and physical properties are used to identify substances. Chemical properties involve changes in composition while physical properties do not. 3) Energy drives all chemical and physical changes. It is transferred and transformed during reactions but cannot be created or destroyed. Exothermic reactions release energy while endothermic reactions absorb energy.
Introduction
- 1. WHAT IS THERE TO KNOW ABOUT CHEMISTRY ?
- 2. CHEMISTRY Matter Composition change energy physical chemical Laws/Principles/Theories properties has has undergoes Relates to Can bestudies Predict interpret effectsstudies basis of distinction : composition
- 4. • Matter – anything that has mass and occupies space • Laws/Theories- mathematical statements of behaviour of matter • Properties- characteristics that describe matter; use to determine its usefulness » Physical- properties which can be observed/measured without a change in the composition of the substance » Chemical – properties which can be observed/measured only after a change in the composition of the substance » Intensive – does not depend upon amount of the substance » Extensive – depends upon amount of the substance
- 5. Every pure substance has its own unique set of properties( • - serve to distinguish it from all other substances • Are intensive properties-properties which are independent of amount of the substance • Chemical properties are intensive properties • Fact: • Sample weighs 4.02 g, has a volume 0f 229 mL. • Tells nothing about the identity of the substance • Mass & volume – extensive properties- they depend on amount Beyond that the substance may be identified on the basis of its chemical properties
- 6. Chemical change- change in the composition of the substance Chemical equation- expression/language of a chemical change
- 7. • Matter is anything that has mass and occupies space. Matter can be invisible. Air is matter, but it cannot be seen. Matter appears to be continuous and unbroken. Matter is actually discontinuous. It is made up of tiny particles call atoms.
- 8. An apparently empty test tube is submerged, mouth downward in water. Only a small volume of water rises into the tube, which is actually filled with invisible matter– air.
- 9. Classification of matter: A pure substance is always homogeneous in composition, whereas a mixture always contains two or more substances and may be either homogeneous or heterogeneous.
- 10. Substance • A particular kind of matter that has a fixed composition and distinct properties. • Examples • ammonia, water, and oxygen.
- 11. Homogeneous Matter Matter that is uniform in appearance and with uniform properties throughout. Examples ice, soda, solid gold
- 12. Heterogeneous Matter • Matter with two or more physically distinct phases present. • Examples • ice and water, wood, blood
- 14. Phase • A homogenous part of a system separated from other parts by physical boundaries. • Examples • In an ice water mixture ice is the solid phase and water is the liquid phase
- 15. Mixture • Matter containing 2 or more substances that are present in variable amounts. Mixtures are variable in composition. They can be homogeneous or heterogeneous.
- 16. Homogeneous Mixture (Solution) • A homogeneous mixture of 2 or more substances. It has one phase. • Example • Sugar and water. Before the sugar and water are mixed each is a separate phase. After mixing the sugar is evenly dispersed throughout the volume of the water.
- 17. Heterogeneous Mixture • A heterogeneous mixture consists of 2 or more phases. • Example • Sugar and fine white sand. The amount of sugar relative to sand can be varied. The sugar and sand each retain their own properties.
- 18. Mixture of iron and sulfur Compound of iron and sulfur Has no definite formula: consists of Fe and S. FeS Contains Fe and S in any proportion by mass. 63.5% Fe and 36.5% S by mass. Fe and S can be separated by physical means. Fe and S can be separated only by chemical change.
- 19. Energy – driving force of all changes/capacity to do work Energy Types Potential – stored energy Energy at work motion position Vibrational motion Of a plucked guitar Translational motion Of a moving bullet Kinetic motion of Moving molecules Due to has HEAT Most Common form
- 20. Thermodynamics • Literally means “movement” of heat • As it applies to chemistry it refers to all aspects of chemical systems that involve changes in energy of any type.
- 21. Laws of Thermodynamics • First Law • Defines the energy change for a process in terms of the difference between heat absorbed and work done • Second Law • Puts a restriction on the amount of heat that may be converted into work and defines a quantity called entropy
- 22. 22 In all chemical changes, matter either absorbs or releases energy.
- 23. 23 Law of Conservation of Energy Energy can be neither created nor destroyed, though it can be transformed from one form of energy to another form of energy. Bookeeping of energy
- 24. Situation Seem to Be Actual Direction of Energy Flow A + B >>> C C < A + B Energy was destroyed Some of A and B was converted into energy and was inevitably lost as HEAT EXOTHERMIC C > A + B Energy was created A and B absorbed Heat from outside to form C ENDOTHERMIC
- 25. 25 An energy transformation occurs whenever a chemical change occurs. • If energy is absorbed during a chemical change (endothermic ), the products will have more chemical potential energy than the reactants. • If energy is given off in a chemical change (exothermic ), the products will have less chemical potential energy than the reactants.
- 26. 26 Energy Release From Chemical Sources Type of Energy Energy Source Electrical Storage batteries Light A lightstick. Fuel combustion. Heat and Light Combustion of fuels. Body Chemical changes occurring within body cells.
- 27. 27 Chemical Changes Caused by Absorption of Energy Type of Energy Chemical Change Electrical Electroplating of metals. Decomposition of water into hydrogen and oxygen Light Photosynthesis in green plants.
- 28. Do all changes spontaneously occur(bound to happen)? What will bound to happen in each of the following situation?
- 29. firewood
- 30. ice
- 31. Attainment of low energy state Endothermic heat flow Increase in entropy Exothermic heat flow ice firewood What are the reasons behind in the spontaneous changes of the above situations ?
- 32. The rationale of an spontaneous change are Attainment of low energy state Attainment of high entropy Entropy- degree of disorderliness