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Welcome !!!! Dr. Leslie Sombers Lingjiao Qi In the top left, click Guest Login --> Create new account. In the top right, click orange button ‘register here’. Click the link in the when it arrives. Under ‘search courses’, type in ‘Lee County ’. Enter as the key code.
A. Develop a thinking map or brainstorm a list to show what you know about Chemistry. B. Share your map with your group/neighbor. C. Place your map on the wall. D. With your group, develop a definition for chemistry. Write it on your sentence strip and post it for others to see. Your assignment:
What is Chemistry? The study of all substances and the CHANGES they undergo. Referred to as the Central Science because it overlaps so many other sciences. It all begins with curiosity!
Some Definitions…. Hypothesis: Theory: Variable: Fact: Law: a proposed explanation for a phenomenon. Generally based on observations a value that may change within the scope of a given problem Valid observation. Scientific facts are verified by repeatable experiments. A scientific law is a statement based on repeated experimental observations that describes some aspect of the world. Hypothesis that has been tested over long periods
Classifying Matter Matter is classified by the number of phases it contains. Any part of a system with uniform composition and properties is called a phase. Matter can be classified as either Homogeneous or Heterogeneous.
Mixtures Mixtures are a physical blend of 2 or more kinds of matter. Mixtures can be either homogeneous (solutions) or heterogeneous. Separation of mixtures is done by physical means such as magnets, distillation, chromatography and filtration.
Pure Substances A pure substance has a fixed composition. Elements and compounds are pure substances. Unlike mixtures, every sample of a pure substance has exactly the same characteristic properties and composition.
Elements and Compounds An element is a collection of the same type of atom. They are the simplest form of matter that can exist under normal lab conditions. Compounds consist of two or more elements that are chemically combined. They can be separated only by a chemical change. Making a compound….
Extensive vs. Intensive Extensive Properties Depend on the amount of matter present Mass, volume, length, height, amount of energy, etc. Intensive Properties Do not depend on the amount of matter present Density, boiling point, melting point, color, ability to conduct electricity, etc.
Metric System The metric system is based on a base unit that corresponds to a certain kind of measurement Length = meter Volume = liter Weight (Mass) = gram Prefixes plus base units make up the metric system – Example: Centi + meter = Centimeter Kilo + liter = Kiloliter
Metric System The three prefixes that we will use the most are: – Kilo= 1000 – centi = 1/100 (one hundredth) – milli= 1/1000 (one thousandth) How do you remember all of them? Kissing Hairy Dark space dogs causes mono King Henry Died by Drinking Chocolate Milk Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000) https://www.youtube.com/watch?v=IhtgKHYZti0
Metric System So if you needed to measure length you would choose meter as your base unit – Length of a tree branch 1.5 meters – Length of a room 5 meters But what if you need to measure a longer distance, like from your house to school? – Let’s say you live approximately 10 miles from school 10 miles = meters – is a big number, but what if you could add a prefix onto the base unit to make it easier to manage: meters = kilometers (or 16.1 if rounded to 1 decimal place)
Metric System These prefixes are based on powers of 10. What does this mean? – From each prefix every “step” is either: 10 times larger or 10 times smaller – For example Centimeters are 10 times larger than millimeters 1 centimeter = 10 millimeters Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000)
Metric System – Centimeters are 10 times larger than millimeters so it takes more millimeters for the same length 1 centimeter = 10 millimeters Example not to scale 1 mm 1 cm
Metric System For each “step” to right, you are multiplying by 10 For example, let’s go from a base unit to centi 1 liter = 10 deciliters = 100 centiliters 2 grams = 20 decigrams = 200 centigrams ( 1 x 10 = 10) = (10 x 10 = 100) (2 x 10 = 20) = (20 x 10 = 200) Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000)
Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000) Metric System An easy way to move within the metric system is by moving the decimal point one place for each “step” desired Example: change meters to centimeters 1 meter = 10 decimeters = 100 centimeters or 1.00 meter = 10.0 decimeters = 100. centimeters
Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000) Metric System Now let’s try our previous example from meters to kilometers: meters = decameters = hectometers = kilometers So for every “step” from the base unit to kilo, we moved the decimal 1 place to the left (the same direction as in the diagram below)
Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000) Metric System If you move to the left in the diagram, move the decimal to the left If you move to the right in the diagram, move the decimal to the right
Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000) Metric System Now let’s start from centimeters and convert to kilometers centimeters = ? kilometers
Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000) Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000) Metric System Now let’s start from meters and convert to centimeters 5 meters = ? centimeters Now let’s start from kilometers and convert to meters.3 kilometers = ? meters
Metric System Summary – Base units in the metric system are meter, liter, gram – Metric system is based on powers of 10 – For conversions within the metric system, each “step” is 1 decimal place to the right or left – Using the diagram below, converting to the right, moves the decimal to the right and vice versa Kilo (1000) Hecto (100) Deca (10) Base Units meter gram liter deci (1/10) centi (1/100) milli (1/1000)
Purpose: to provide a set of physical science activities to help teach major concepts in the study of matter and to help students develop their abilities in scientific inquiry Developed to work across grades 3-8 Cover basic concepts with flexibility incorporated Common, safe and inexpensive materials Material is based on the National Science Education Content Standards for Physical Science and Science as Inquiry Scientific questions are their investigation Physical properties Physical change Dissolving solids, liquids and gases Chemical change States of matter Density ACS – Inquiry in Action. A guided-inquiry approach.
Each investigation Begins with an intro activity to motivate discussion Together, teacher and students develop a question to investigate and design an experiment to answer the question Students plan their experiment, record their results, and draw conclusions. Goal: students will acquire both the skills of scientific inquiry and the concepts of the physical science curriculum
Essential Features of Inquiry: 1.Students begin with a question that can be answered in a scientific way 2.Students rely on evidence in attempting to answer the question 3.Students form an explanation to answer the question based on the evidence collected 4.Students evaluate their explanation
Science as inquiry: Abilities necessary to do scientific inquiry
Science as inquiry: Understandings about scientific inquiry
Physical science content standards
Question to investigate A question at the beginning of each activity serves as a guide for designing and conducting the experiments to answer that question. All the activities within an investigation lead up to or contribute to the overall objective of the investigation. Procedure Procedures are examples or models of ways to design and conduct an experiment to answer the question to investigate. Because student input in the experimental design is encouraged, the procedure may be modified or completely changed. The procedure is offered as a guide to show one way an activity can be conducted. Expected results The expected results describe what would happen if the activities were conducted exactly as written. These should be used as a guide, as the procedures students develop may vary. Activity sheets Each activity has a corresponding activity sheet, which guides students as they conduct the activity. The activity sheets help students plan their experiments, record their observations, draw conclusions based on observations, offer explanations, and apply their learning. When needed, the activity sheets also contain science content. Assessment One scoring rubric is included with each investigation. This can be used as a formative assessment of the students’ work on the activity sheets and their performance doing the hands-on activities that were a part of the investigation. A separate summative assessment for the investigation, called Review and apply, is included at the end of each investigation.
The Power of Polarity Atoms have a certain number of protons in their nucleus and the same number of electrons around the nucleus. Protons – POSITIVE CHARGE Electrons – NEGATIVE CHARGE Because the nucleus contains protons, it has an attraction for electrons. Since an atom has the same number of positively-charged protons as negatively-charged electrons, an atom has no overall or net charge. IT IS NEUTRAL. O H H Water (H 2 O) is made up of 2 hydrogen atoms bonded to one oxygen atom. It is the special character of this oxygen-hydrogen bond that makes water such a good dissolver
Atoms can form a covalent bond When 2 atoms get near each other, the protons in the nucleus of each atom have a certain attraction for the electrons in the other atom. If the attractions are just right, one or more electrons from each atom can end up moving around the nuclei of BOTH atoms. Even though the atoms in the water molecule share electrons, the total number of electrons is still equal to the total number of protons. Therefore, the water molecule has no overall or net charge.
The oxygen-hydrogen bond Because the oxygen has a greater attraction for electrons than the hydrogens have, the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen than they do around the hydrogens. Because electrons have a negative charge, this makes the area around the oxygen atom slightly negatively charged. It also leaves the area around the hydrogen atoms slightly positively charged. O HH O H H BEFORE AFTER
A picture of water The charge density model O H H O HH The space-filling model O H H The ball and stick model
The power of polarity The molecules in liquid water associate very closely with one another They orient themselves according to their polarity (the positive area of one molecule is attracted to the negative area of another) Attractions between water molecules are constantly breaking and new ones are forming with other water molecules The attraction water molecules have for other polar or charged particles is what makes water so effective at dissolving many substances
The molecular structure of sucrose molecules Sugar dissolves in water because of the special structure of the water molecule, but also because of the structure of the molecules that make up sugar (sucrose). C 12 H 22 O 11 Red = oxygen (slightly negative) gray = hydrogen (slightly positive)
Dissolution – 2 sucrose molecules dissolving in water
Investigation 1: Scientific questions and their investigation Key concepts for students In a scientific experiment, a “variable” is something that can affect the outcome of the experiment. When designing a scientific experiment, it is necessary to identify and control variables. In an experiment to find out if a certain variable affects the outcome, only that variable should be allowed to vary and all other variables should be kept the same. The temperature of a solvent affects the speed of dissolving. Learning objectives Students will be able to: Ask scientific questions that they can investigate. Identify and control variables as they design an experiment to answer the questions. Be able to make predictions, design and conduct tests, record their observations, and draw logical conclusions. Understand the meaning of the “characteristic properties” of an object or substance. Identify variables that affect dissolving.
Investigation 1: Scientific questions and their investigation Investigation questions What happens when the colored coating of an M&M gets wet? What happens when one M&M is placed in water? Do some M&M colors dissolve in water faster than others? What would the colors look like if we place two or more M&M’s in a plate of water? Is the “line” that forms when two colors meet a special property of M&M’s? Does the temperature of the water affect how fast the colored coating dissolves from an M&M? Does the amount of sugar already dissolved in water affect how fast an M&M coating dissolves?
Chemistry review: Water A water molecule has no overall or “net” charge. It is neutral. Because of the way oxygen and hydrogen are bonded together, water has an area of positive charge and an area of negative charge. This makes the water a polar molecule. Because of water’s polarity, water molecules are attracted to each other. Sugar (sucrose) also has oxygens and hydrogens bonded to each other. This gives sucrose many areas of positive and negative charge. Water and sucrose are attracted to one another based on the attractions of opposite charges. When the attraction that water molecules have for sucrose overcomes the attraction sucrose molecules have for each other, the sucrose dissolves. The polar nature of water is what makes water so good at dissolving many substances.
The structure of water
Review - How are ions made from neutral atoms? Yes no metal nonmetal Yes no Ion POGIL
2. What distinguishes a neutral atom from an ion? A change in the number of electrons 3a. Where is the ion charge located in the isotope symbol? Upper right 3b. Is a charge indicated on the neutral atoms? If yes, where is it located? There is no charge indicated 4. Which subatomic particle carries a positive charge? 5. Which subatomic particle carries a negative charge? protons electrons 6. Propose a mathematical equation to calculate the charge on an ion from the number of protons and electrons in an ion. Confirm that your equation works using two positive ion examples and two negative ion examples from model 1 Number of protons – number of electrons = charge
cation anion Ga cationanion Br Could a +3 ion of aluminum be made by adding three protons to an aluminum atom? No, changing the number of protons would change it into a different element 9. “When you add an electron, you get a positive charge because adding is positive in math.” a. Explain why this student is incorrect When you add an electron, you get a negatively charged ion. b. Provide a better description of how math relates to electrons and ion formation The electron has a negative charge, so you are adding a negative number
anions cations hydrogen
Physical Changes Physical change alters the substance without changing its composition or chemical identity. Boil, melt, cut, break, split, grind, crush, bend, condense, freeze, dissolve and crack are examples of physical changes.
Physical Properties A physical property is a condition that can be measured or observed without changing the identity of the substance. Examples of physical properties include color, solubility, odor, hardness, density, melting point and boiling point, etc.
Chemical Properties The ability of a substance to undergo a chemical reaction to form a new substance is called a chemical property. Chemical properties are observed when a substance undergoes a chemical change.
Chemical Change A change in which one or more substances are converted into different substances is called a chemical change or chemical reaction. C + O 2 CO 2 (reactants) (product)
Look for terms such as... burn rot rust decompose ferment explode oxidize corrode grow precipitate gas formation digest Combustion – powering the space shuttle
Physical Change in Solids The Chemistry of Solubility Dissolving NaCl Review solutions – solute vs solvent
Investigation 2: Physical properties and physical change in solids Key concepts for students ● Solubility is a characteristic property of a substance. ● To measure equal amounts of different solids for a solubility test, it is better to use mass than volume. ● When comparing solubilities of different solids, all variables should be kept the same except for the type of solid used. ● The way a substance recrystallizes is a characteristic property of that substance. ● Solubility and recrystallization can be used to help identify an unknown substance. Learning objectives Students will be able to: ● Develop an understanding of the meaning of characteristic properties of substances by testing and comparing different household crystals. ● Recognize that solubility is a characteristic property of a substance. ● Identify an unknown crystal by comparing its characteristic physical properties with those of four known crystals. ● Measure equal amounts of crystals by mass rather than volume. ● Identify possible variables and suggest ways to control them as they help design valid scientific investigations.
Investigation questions How can you tell if crystals that look the same are really the same or different? Can you identify an unknown crystal by comparing its appearance to other known crystals? Can you identify the unknown crystal by crushing the different crystals and comparing them? Do some of the crystals dissolve more or less than others? What is the best way to measure equal amounts of crystals? Can you identify the unknown crystal by the amount that dissolves in water? Can you identify the unknown crystal by the way it looks when it recrystallizes? Investigation 2: Physical properties and physical change in solids
Physical Change in Solids - Summary Physical change is a change that alters the form or appearance of a material without changing the chemical composition. One example of a physical change is dissolving. Salt is made of ions that are ionically bonded together in a crystal. Sugar is made of molecules that are bonded together based on the positively and negatively charged areas. The positive and negative areas of water molecules are attracted to the oppositely charged ions in salt and to the positive and negative areas on sugar molecules. Because salt and sugar are made up of different atoms that bond together differently, water is attracted to them differently. Water interacts and dissolves salt and sugar in characteristic ways That’s why solids that may look similar behave differently.
Physical Properties and Physical Change in Liquids
Investigation 3: Physical properties and physical change in liquids Key concepts for students ●Different liquids have different characteristic properties ● A solution made from water and another substance will have characteristics based on the interaction between water and the other substance. ● The way a liquid behaves on a surface depends on the characteristics of the liquid and the characteristics of the surface. ● The way a liquid combines with water depends on the characteristics of the liquid and the characteristics of water. Learning objectives ● Recognize that different liquids have unique characteristic properties. ● Identify and control variables as they design and conduct tests on each of the liquids. ● Identify unknown liquids based on the results of their tests. ● Understand that the way liquids behave on a surface has to do with the interaction between the characteristics of the liquid and the characteristics of the surface. ● Understand that the way liquids combine with water has to do with the interaction between the characteristics of the liquid and the characteristics of water.
Investigation questions How can you tell if liquids that look the same are really the same or different? ● Can you distinguish between four clear colorless liquids based on the way they look on a brown paper towel? ● How can you identify an unknown liquid based on the way it behaves on different paper surfaces? ● Can you tell a difference between liquids by the way they look when they combine with water? ● How can you use the characteristic way each liquid combines with water to identify the unknown liquids? Investigation 3: Physical properties and physical change in liquids
Dissolving Solids, Liquids and Gases Solubility POGIL
Investigation 4: Dissolving Solids, Liquids and Gases Key concepts for students ● Dissolving applies to solids, liquids, and gases. ● Dissolving involves the interaction between the solvent and the solute. ● The extent to which a substance dissolves in a liquid is a characteristic property of that substance. ● Heat increases the solubility of most solids. ● Heat does not increase the solubility of all solids by the same amount. ● Heat decreases the solubility of most gases. Learning objectives Students will be able to: ● Identify and control variables to design and conduct valid experiments. ● Develop a definition of “dissolve” that applies to solids, liquids, and gases. ● Use observations and results of experiments to develop explanations to answer a question. ● Explain that the solubility of a substance depends on the characteristics of both the solute and the solvent giving each substance a unique solubility. ● Draw pictures and write captions showing the stages of a solid dissolving. ● Explain that heat affects the solubility of solids and gases differently.
Investigation questions Can solids, liquids, and gases all dissolve? ● How can you tell when a substance is dissolved? ● Does colored sugar dissolve equally well in water, vegetable oil, and alcohol? ● Does cocoa mix dissolve better in hot water or cold water? ● Do salt and sugar dissolve better in hot water than in cold water? ● Do all liquids dissolve in water? ● Can a gas dissolve in a liquid? ● Does temperature have an effect on how quickly dissolved gas escapes from a soda? ● How can you make a lemon soda that keeps as much carbonation as possible? Investigation 4: Dissolving Solids, Liquids and Gases
Dissolving - Summary Solids, liquids, and gases can all dissolve. Dissolving depends on the molecules of the substance doing the dissolving, called the solvent, and the molecules of the substance being dissolved, called the solute. Dissolving is the process in which these molecules interact and attract each other to form a solution. The extent to which a substance dissolves is a characteristic property of that substance called its solubility. Water is a good dissolver because of its areas of positive and negative charge. The mutual attraction between water molecules and other substances with positive and negative charges causes these substances to dissolve.
Chemical Change Acid/Base POGIL Calculating pH POGIL
Acid: A substance that releases H+ ions in an aqueous solution “aqueous” means: water
Characteristics of Acids: Acids have a sour taste Acids react with metals Acids contain Hydrogen Many are poisonous and corrosive to skin H
Strong Acids (break down completely to give off many H+ ions)
Weak Acids (only partially breaks down, gives less H+)
Acids and Bases Acids: Some common acids in our daily life: Ethanoic Acid, CH 3 COOH: found in vinegar, tomato juice Citric Acid, C 6 H 8 O 7 : found in citrus fruits Lactic Acid: found in sour milk, yogurt Tannic Acid: Found in tea Tartaric Acid: Found in grapes What about those commonly found in our lab? Hydrochloric acid, HCl Sulfuric Acid, H 2 SO 4 Nitric Acid, HNO 3 Which of these is found in batteries? Sulfuric Acid
Base: A substance that releases OH- ions in an aqueous solution
Characteristics of Bases: Bases usually taste bitter Bases feel slippery Bases contain hydroxide ions STRONG bases are also poisonous and corrosive to skin OH -
Strong BasesThe Formulae Lithium hydroxide Sodium hydroxide Potassium hydroxide Rubidium hydroxide Caesium hydroxide Barium hydroxide Calcium hydroxide Strontium hydroxide LiOH NaOH KOH RbOH CsOH Ba(OH) 2 Ca(OH) 2 Sr(OH) 2 Common Bases: (Hydroxides of Group 1 and Group 2 Metals are STRONG) All others are WEAK
Some bases (VERY FEW) don’t have OH- Most commonly: ammonia NH3
Reactions between acids and bases When and acid and a base react with each other, the characteristic properties of both are destroyed. This is called neutralization.neutralization
Reactions between acids and bases General formula for acid base reaction: Acid+Base→ H2OH2O+ Salt “Salt” means any ionic compound formed from an acid/base reaction NOT JUST NaCl !! Neutralization Reaction Animation
Neutralization HCl + NaOH → H 2 O + NaCl acidbase water salt
Neutralization Another Example HNO 3 + KOH → H 2 O + KNO 3 H OH K NO 3 acidbase water salt
Indicators An indicator is a compound that will change color in the presence of an acid or base Universal indicator (pH paper) Used for the full pH range Red Litmus-Turns blue in base Blue Litmus-Turns red in acid Phenolphthalein-Turns pink in base
pH pH stands for “potential hydrogen” and is a measure of how many H+ ions there are in solution. The MORE H+ there are, the LOWER the pH will be. pH = - log [H + ]
pH Scale Shows the range of H+ concentrations High H+ concentrationLow H+ concentration Virtual demonstration - Detecting acid/base
Investigation 5: Chemical Change Key concepts for students ● Substances react chemically in characteristic ways. ● Evidence that a chemical reaction has occurred includes: production of a gas, change in temperature, color change, and formation of a precipitate. ● A chemical reaction can be controlled by adjusting the amount of reactants. ● A chemical reaction can result in an increase in temperature (exothermic) or a decrease in temperature (endothermic). ● The color change of an acid–base indicator can help classify a solution as an acid or a base, identify when a solution has been neutralized, and compare the amount of acid or base in a solution. ● In a chemical reaction, the bonds holding one atom to another are broken, atoms rearrange, and then combine in new ways to create one or more different substances. ● In a chemical reaction, the atoms that make up the reactants are never destroyed or disappear. They rearrange and bond in new ways to form the products. Learning objectives Students will be able to: ● Design a testing procedure to compare the chemical reactions of different substances. ● Use the characteristic chemical reactions to identify an unknown substance. ● Recognize that production of a gas, change in temperature, color change, and formation of a precipitate are evidence of chemical change. ● Use a thermometer and graduated cylinder accurately. ● Control chemical reactions by adjusting the amount of the reactants. ● Use the color changes of an acid-base indicator to classify and compare different substances. ● Determine whether a new substance is created during a chemical reaction.
Investigation questions ● Do powders that look the same have the same chemical reactions? ● How can you use the characteristic ways substances react to tell similar-looking substances apart? ● How can you identify an unknown powder? ● What are the active ingredients in baking powder? ● Aside from bubbling, what else happens during a reaction between baking soda and vinegar? ● How can you control the amount of gas produced in a baking soda-and-vinegar reaction? ● Can the temperature increase during a chemical reaction? ● How can you tell if a substance is an acid, a base, or neutral? ● How can you return the color of a red cabbage indicator solution back to blue? ● How can neutralizing acids help you compare the amount of acid in different solutions? ● What happens when soap is added to hard water? Investigation 5: Chemical Change
Relevant National Science Education Standards: K–4 Physical science Properties of objects and materials Objects have many observable properties Science as inquiry Abilities necessary to do scientific inquiry Ask a question about objects. Plan and conduct a simple investigation. Use simple equipment and tools to gather and extend the senses. Use data to construct a reasonable explanation. Communicate investigations and explanations. Understandings about scientific inquiry Scientific investigations involve asking and answering a question. Types of investigations include describing objects…and doing a fair test. Good explanations are based on evidence from investigations 5-8 Physical science Properties and changes of properties in matter A substance has characteristic properties Science as inquiry Abilities necessary to do scientific inquiry Identify questions that can be answered through scientific investigations. Design and conduct a scientific investigation. Use appropriate tools and techniques to gather, analyze, and interpret data. Develop descriptions, explanations, predictions, and models using evidence. Think critically and logically to make the relationships between evidence and explanations. Communicate scientific procedures and explanations. Understandings about scientific inquiry Different kinds of questions suggest different kinds of scientific investigations. Scientific explanations emphasize evidence and have logically consistent arguments. Scientific investigations sometimes result in new ideas and phenomena for study that can lead to new investigations.
Chemical Change - Summary A chemical reaction happens when one or more substances change into entirely new substances with different properties. The clues of a chemical reaction are production of a gas, change in temperature, color change, production of a precipitate. In a chemical reaction, it takes energy to break the bonds in the reactants and energy is released when bonds are formed in the products. If more energy is required to break the bonds than is released when new bonds are formed, the reaction is endothermic.