Chemistry01A_Lec1s-2010

Chemistry01A_Lec1s-2010 - Outline 1 Jan-5-2010 Why study...

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Chem1A 1 Outline 1 Jan-5-2010 Why study Chemistry? Fundamental definition The scientific approach and problem solving Measurements, numbers, units and dimensions Temperature conversions The scientific approach and problem solving Measurements Significant Figures; Precision & Accuracy
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Chem1A 2 Chemistry Why study chemistry? -- Used in all sciences -- It’s a part of life itself: breathing, growing, thinking -- Tremendous applications Creation of new products Drug design and discovery Greener environment
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Chem1A 3 Chemistry Is the study of matter (anything that occupies space and has mass), its properties , the changes that matter undergoes, and the energy associated with these changes.
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Chem1A 4 Classifying Matter Slide courtesy of Lee Wilson
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Chem1A 5 Substances and Mixtures Substance: Fixed composition as in pure elements and compounds. Ex: sodium, glucose, water Mixture: Variable compositions, two or more substances. Ex: salt water, milk, juice. Separable into substances through physical processes
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Chem1A 6 Physical Change Change in form (state) but not in kind. Same substance. Can be reversed by just changing temperature. No new substances formed. Melting ice, H 2 O(s) → H 2 O(l) ice (solid) turns into water (liquid)
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Chem1A 7 Chemical Change (reaction) substance(s) changed into new substance(s). (May include change in state (physical change)). (Can’t be reversed by just changing temperature.) New substances formed. Example: rusting of iron 4 Fe(s) + 3 O 2 (g) → 2 Fe 2 O 3 (s) iron and oxygen form an iron oxide
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Chem1A 8 Distinguishing Between Physical and Chemical Change PROBLEM: Decide whether each of the following process is primarily a physical or a chemical change, and explain briefly: PLAN: “Does the substance change composition or just change form?” SOLUTION: (a) Frost forms as the temperature drops on a humid winter night. (b) A cornstalk grows from a seed that is watered and fertilized. (c) Dynamite explodes to form a mixture of gases. (d) Perspiration evaporates when you relax after jogging. (e) A silver fork tarnishes slowly in air. (a) physical change (b) chemical change (c) chemical change (d) physical change (e) chemical change
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9 Scientific Approach: Developing a Model Observations : Natural phenomena and measured events; universally consistent ones can be stated as a natural law. Hypothesis: Tentative proposal that explains observations. Experiment: Procedure to test hypothesis; measures one variable at a time. Model (Theory): Set of conceptual assumptions that explains data from accumulated experiments; predicts related phenomena. Further Experiment:
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Chemistry01A_Lec1s-2010 - Outline 1 Jan-5-2010 Why study...

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