Understanding the rules It’s not enough to remember the rules for conducting a lab experiment safely – you need to understand WHY those rules exist Like any lesson in science, you’ll remember it better if you Understand the importance of the concept, or Experience the concept first-hand Since I’d rather you not learn the importance of safety glasses by blinding yourself, focus on the WHY of the following rules.
QUESTION: What safety equipment is mandatory for every lab, and what is optional?
Rule #1 – Wear the proper safety equipment ANSWER: Safety glasses are mandatory, however, prescription glasses are an acceptable replacement ** Safety glasses must be worn on the face, not as a hair accessory, even if you find them uncomfortable. ** ** We strongly discourage you from wearing contact lenses into the lab, even if you are wearing safety glasses ** Lab coats are mandatory any time chemicals are being used (e.g. you don’t need them for a bio lab on microscopes) Closed-toe footwear is required – no sandals or flip flops Gloves are only needed during dissections, where you are likely to be handling a biohazardous specimen
QUESTIONS: Suppose you know your three solutions are salt water, sugar water and vinegar, and that none of these substances will hurt you. Why should you still not taste them? Why is it not even a good idea to bring in a water bottle or chewing gum?
Rule #2 – Don’t eat or drink in the lab ANSWERS: We cannot guarantee that the solutions are pure, that the glassware is clean, or that there are no chips in the beaker You shouldn’t stake your life on being 100% right about any experiment You could reach for your water and get something else You don’t want anything else on your lab bench other than the required materials Even water can be a dangerous chemical if mixed with the right substance Gum can absorb fumes and increase your chance of ingesting something
Rule #3 – Leftover chemicals QUESTION: What should be done with any used or unused chemical once they have been taken from the original container (the source container)?
Rule #3 – Leftover Chemicals ANSWER: ALWAYS put any chemicals you’ve taken from the stock beaker in the waste beaker OR If it is safe to do so; with the tap running to dilute it, you can pour it down the drain. WHY: The chemicals could have been contaminated by something already in your beaker so it can never go back to the original container The new chemical you made will have different properties Some solutions, such as those containing heavy metals, will pollute local water supplies, or corrode the pipes
Rule #4 – Wash your hands thoroughly QUESTION: When should you wash your hands in the lab? POSSIBLE ANSWERS: A) Before starting the experiment B) After handling each chemical C) At the end of the lab activity D) Before you eat your lunch
Rule #4 – Wash your hands thoroughly CORRECT ANSWER: C) At the end of the lab activity unless you spill anything on your hands while you’re working, there’s no need to wash your hands in between each chemical you should wash your hands at the end, even if they appear clean, because some chemicals are invisible and others just plain stink.
Rule #5 – Clean up any spilled substances immediately QUESTION: Why should you check with your teacher first before you clean something up? POSSIBLE ANSWERS: A) Because you should collect the spilled liquid and try to reuse it B) Because your teacher wants as many reasons as possible to yell at you C) Because there may be specific instructions for cleaning up that particular solution D) Because your teacher spends less money on her clothes than you, so she doesn’t mind the risk
Rule #5 – Clean up any spilled substances immediately CORRECT ANSWER: C) Because there may be specific instructions for cleaning up that particular solution (Although your teacher does probably spends less money on her clothes than you) For instance, if you spill an acid, we will first neutralize it with a basic solution (baking soda solution) if you spill a base, we will first neutralize it with an acidic solution (vinegar solution) some compounds should be diluted first before wiping them up some compounds stain your skin, and you don’t want to be known as the “splotchy kid”
Rule #6 – Pour chemicals properly QUESTION: Which photo demonstrates the safe way of pouring chemicals?
Rule #6 – Pour chemicals properly ANSWER: Actually none of them! (Photo #1 is the safest) If you spill something, immediate stop pouring and check for a break in your glassware Precise measurements are made at eye level, not above or below your line of sight
Rule #6 – Pour chemicals properly ANSWER: Don’t get your lab partner to hold on to your glassware while you pour Especially with test tubes and graduated cylinders (which are narrow), never pour chemicals into containers held in your hands – place the container on the counter or use a test tube rack
Rule #7 – Always listen to the teacher’s instructions QUESTION: You should know what you’re doing in the lab BEFORE you go in, so what are some reasons why you should listen to the teacher’s instructions during the lab?
Rule #7 – Always listen to the teacher’s instructions ANSWERS: There may have been a change to the procedure due to a lack of supplies There could be some kind of emergency Because your teacher charges a “stupid question tax” of 5 marks if you ask her something that is in the lab procedure or was said out loud while you weren’t listening
Rule #8 – Label any containers you put chemicals in QUESTION: One of these solutions is sugar water, one is an acid strong enough to dissolve concrete, and one will make you go blind if you drink it. Which is which?
Rule #8 – Label any containers you put chemicals in ANSWER: Actually, they’re all water, but hydrochloric acid, methanol, and sugar water are all clear, colourless solutions indistinguishable by sight. SO? Even if you think you can “keep track” of which substance is which, label your containers to minimize your risk, and your error
Rule #9 – What to do with broken glassware QUESTION: What’s the proper procedure if you break glassware? ANSWER: 1) Inform your teacher 2) Make sure any other students in the area are alerted 3) Your teacher will collect the large pieces, and we will sweep up the smaller pieces 4) If necessary, we will neutralize any spilled liquid 5) Broken glass goes in a special bin – do not simply throw it out into the garbage.
Rule #10 – Safely detect the odor of a substance QUESTION: How should you go about safely detecting the odor of a substance? ANSWER: You hold the container safely away from your face and use your hand to “waft” the scent towards your nose. WHY: The smell may be too strong / irritating to get a nose-full You should never put your face directly over a container in case of splattering or fumes
Rule #11 – Tie hair back and roll up loose sleeves
QUESTION: What are three reasons why it could be dangerous to have long hair or loose sleeves unsecured?
Rule #11 – Tie hair back and roll up loose sleeves ANSWER: Both hair or clothing could catch on fire Loose sleeves can knock over glassware, resulting in broken glass or spilling harmful chemicals Both hair and clothing can absorb chemicals and further exacerbate a chemical burn/ irritation
Rule #12 – Mixing acids and water QUESTION: What’s the proper way of mixing an acid and water? POSSIBLE ANSWERS: A) Pour the acid into the water – it’s less likely for acid to splash out of the container B) Pour the water into the acid – you’re less likely to get acid on your hands this way C) It doesn’t matter what order you mix two chemicals in, the result will be the same.
Rule #12 – Mixing acids and water CORRECT ANSWER: A) Pour the acid into the water – it’s less likely for acid to splash out of the container You always pour any acids into water rather than vice versa because it's much more likely that the liquid being poured into will splash out of the beaker. If it's just water, then it’s not a problem; but if acid gets on your clothes or hands you can get burned badly.
Rule #12 – Mixing acids and water CORRECT ANSWER: There’s one other good reason why acid goes in water, and not vice versa - If you add water to acid, the first drops of water will react exothermically with the acid, and bubble all over like it’s boiling (very dangerous!) If you add the acid to the water, the acid reacts/ mixes completely with the water and dissipates. So: “Do like you oughta, add acid to wat-ah”
Rule #13 – Using distilled water instead of tap water QUESTION: What are three reasons why you get more accurate results if you use distilled water instead of tap water? ANSWER: Tap water will have salts dissolved in it that can skew your results Tap water is not necessarily neutral – in fact at O’Leary it has a pH of about 8.5 Tap water comes out at unpredictable rates, distilled water is easier to control the flow
Practice problems: 1. List five steps that should be taken BEFORE entering the lab to perform an experiment? 2. List precautions you can take to prevent: 1. poisoning 2. scalding 3. eye damage
Practice problems: 3. The purpose of a lab is to determine what several “mystery solutions are”. You pick up a fresh test tube, and you pour some “mystery solution” into it and add some solute. You give it a good shake by holding your thumb over the opening and shake it up and down. You put the test tube down into the rack and look down into it to make your observations about the reaction that took place. List as many things as you can that were performed unsafely in the lab. Suggest what should have been done instead that would improve the procedure.
Practice problems: 4. There are six pieces of emergency equipment in the lab. What are they, where are they, and when/how should they be used? 5. What should be done in the following two scenarios? While your lab partner is boiling some water, the fire alarm goes off. Your lab partner has just poured some acid into what you thought was a beaker of water. It starts to bubble rapidly.
Practice problems (Solutions): 1. List five steps that should be taken BEFORE entering the lab or starting to perform an experiment? read the lab COMPLETELY and prepare any pre-lab requirements prepare a pre-lab – predictions, hypotheses, and observations tables should be prepared in advance come dressed in the appropriate clothing bring only the necessary items to the lab (text book, pre-lab, pen/pencil) NO purses, binders, jackets, or iPods put on protective wear: goggles, lab coat, gloves (if necessary) collect solutions/ materials from the front and bring them to your station LABEL all beakers/ materials…keep your station organized! double check with your partners that you ALL understand the procedure – once the lab begins you will lose marks for procedural questions
Practice problems (Solutions): 2. List precautions you can take to prevent: 1. poisoning always wash your hands after the lab, don’t touch your face/ mouth during the lab never use your mouth to open containers etc. 2. scalding never touch test tubes/ beakers that are sitting in water in case they are hot use “oven mitts” or tongs to handle any hot glassware 3. eye damage keep your safety glasses on at all times do not wear contact lenses in chemistry labs (some fumes can cause them to melt to your eyes)
Practice problems (Solutions): 3. The purpose of a lab is to determine what several “mystery solutions are”. You pick up a fresh test tube, and you pour some “mystery solution” into it and add some solute. You give it a good shake by holding your thumb over the opening and shake it up and down. You put the test tube down into the rack and look down into it to make your observations about the reaction that took place. You shouldn’t mix chemicals unless you have a reasonable idea how they will react You shouldn’t shake glassware vertically You shouldn’t use thumb as a stopper Never look directly into a test tube from above (splatters/ fumes can get in your face).
5. What should be done in the following two scenarios? While your lab partner is boiling some water, the fire alarm goes off. Turn off the hot plate/ Bunsen burner. Separate any chemicals that could possibly react while you’re out of the room, then calmly leave the lab. Your lab partner has just poured some acid into what you thought was a beaker of water. It starts to bubble rapidly. The two chemicals are now reacting. Do not touch the beaker. Come get the teacher/ lab tech and tell them what the two chemicals could be
Safety symbols Two different systems of safety symbols have been developed to warn users of potential hazards HSHSWHMIS What does the acronym stand for? Household Safety Hazard Symbols Workplace Hazardous Materials Information System Where is it used?For household products (the average consumer) In labs & industry (people with some understanding of chemistry) Number of symbols48 Colour coded?Yes, three shapes and colours are used to indicate degree of hazard No, all symbols are in circles and are printed in black or red
HSHS Household Safety Hazard Symbols CORROSIVEPOISONOUSEXPLOSIVEFLAMMABLE The product can burn your skin or eyes. If swallowed, it will damage your throat and stomach If you swallow, lick, or in some cases, breathe in the chemical, you could become very sick or die. The container can explode if heated or punctured. Flying pieces from the container can cause serious injury. The product or its fumes will catch fire easily if it is near heat, flames or sparks.
WHMIS the Workplace Hazardous Materials Information System is a national warning system for dangerous chemicals WHMIS symbols are more specific than HSHS, but require a bit more understanding of chemicals
WHMIS - purpose To ensure that all work places across Canada that work with hazardous chemicals have a standardized way for handling and labeling toxic chemicals. Provides: hazard identification product classification ways of safely storing and organizing chemicals labeling methods & material safety data sheets standardized worker training and education
Practice problems: 7. For each room listed, suggest one hazardous chemical that might be found in it. Include the WHMIS symbol that would be appropriate for that hazard. a) kitchen b) bathroom c) garage d) bedroom e) classroom http://toxmystery.nlm.nih.gov/
Material Safety Data Sheets MSDS are detailed information sheets describing the particular properties, hazards, and emergency procedures for a specific chemical Each and every single chemical in the lab has its own sheet, and they are organized into binders alphabetically
Material Safety Data Sheets Information that can be found on the MSDS: material’s identity (e.g. Clorox bleach) brand name e.g. Clorox chemical name e.g. sodium hypochlorite common name e.g. bleach
Material Safety Data Sheets hazardous ingredients lists ingredients as small as 1% e.g. sodium hypochlorite, 5.25% unless listed, the rest of the substance is water physical & chemical hazards / characteristics stability, reactivity, flammability, explosiveness, corrosiveness, compatibility with other materials often listed using WHMIS symbols e.g. stable, incompatible with strong acids, toxic, corrosive, oxidizing
Material Safety Data Sheets health hazards and information acute and chronic effects e.g. corrosive, causes eye and skin burns, causes digestive tract burns, harmful if inhaled, causes respiratory tract irritation carcinogen? (may include human and animal summaries) exposure limits how it gets into the body, what organs it targets, symptoms of overexposure e.g. route: blood; organs: eyes, skin, lungs
Material Safety Data Sheets precautions for handling and storing any safety equipment required (e.g. gloves, eyewash station) or monitoring equipment emergency and first aid procedures how to deal with cases of inhalation, ingestion, and eye or skin contact e.g. ingestion: do not induce vomiting specific fire-fighting information procedures for cleanup and spills identity of the organization responsible for creating the MSDS, date of issue, contact number
Properties of matter “Matter” includes anything that has mass and takes up space To divide up this nearly infinite list of “stuff”, we classify different types of matter based on their properties Properties: the physical and chemical characteristics of a substance Physical properties: appearance and composition of a substance, can usually be determined using the five senses Chemical properties: the reactivity of a substance, can be determined by doing an experiment
Physical properties PropertyDescription boiling pointtemperature of boiling (or condensing) melting pointtemperature of melting (or freezing) malleabilitycan be flattened into sheets without crumbling ductilitycan be stretched into wires without breaking colourcolour (or colourless) transparencyclear (or opaque) statesolid, liquid, or gas at room temperature solubilityability to dissolve (usually in water) crystal formation formation of crystals, appearance of crystals conductivityability to conduct heat or electricity magnetismmagnetic attraction between objects
Chemical properties PropertyDescription ability to burncombustion (causing flame, heat and light) flash pointtemperature needed to ignite a flame behaviour in airtendency to break down, react, tarnish reaction with watertendency to corrode or dissolve reaction with acidscorrosion, sometimes bubble formation reaction to heattendency to melt or decompose reaction to red and blue litmus blue red - acid red blue - base no colour change - neutral
Matter Pure substances Elements Compounds Mixtures Homogeneous Solutions Heterogeneous Mechanical mixtures Suspensions Colloids
Classification of matter Pure substances Mixtures all the particles making up the substance are identical elements –cannot be broken down into other substances e.g. carbon compounds – made up of two or more elements in fixed ratios e.g. water combination of pure substances homogeneous mixtures – the separate components are not visible heterogeneous mixtures – the separate components are visible
Classification of matter Homogeneous mixtures the prefix “homo” means “the same”, meaning all the parts of the solution look the same Solutions one example of a homogeneous mixture in a solution, one substance is dissolved in another the substance dissolving is the solute and the substance it’s dissolving in is the solvent
Classification of matter Mechanical mixtures Suspensions The different substances are clearly visible E.g. trail mix The components of the mixture are in different states E.g. mud in water, aerosol sprays Colloids Similar to a suspension but the suspended substance cannot easily be separated out E.g. whole milk
Classification of matter Not every substance can be easily classified because some substances have features of several categories E.g. motor oil doesn’t have constant properties – it can separate out over time so sometimes it behaves as a solution and sometimes a colloid Pure substances are much easier to classify because Elements are classified in the periodic table Compounds are further classified according to the elements that compose them
Physical change vs. chemical change Physical change – does not alter the chemical characteristics of the substances involved, e.g. phase changes changing from solid to liquid to gas crystallization / dissolving allowing a substance to crystallize, then dissolve back into solution Chemical change – the substances produced have different chemical properties than the substances that reacted
Chemical reactions In a chemical reaction, chemical change occurs when: at least one new substance is formed, with new physical and chemical properties sometimes, those new substances can be observed with phase changes such as bubbles or precipitates sometimes, they can be observed with colour changes or new odours, a change in energy occurs this is often detected by a change in temperature (e.g. it gives off heat)
Homework A1.2 – Check and Reflect Pg.17 #1-7, 9
Chemistry in our world Even before scientists fully understood the structure of the atom or had the technology to study it, people were using chemistry in their daily lives Food chemistry Metallurgy Alchemy
Food chemistry Methods of preserving food heating food – temporarily sterilizes it (kills the micro- organisms) canning – heating the food, then sealing it in an air-tight container freezing – low temperatures prevent the grown of micro- organisms
Food chemistry salting – salt dries the water out of the meat, but also preserves it by drying the water out of any bacteria fermentation – bacteria naturally present on the surface of living organisms converts starches and sugars into acid, preserving the food and giving it a sour flavour
Metallurgy the science of producing and using metals annealing the heating of a metal before it’s hammered, which makes it less brittle this technique has allowed copper to be used for tools, weapons and jewellery for thousands of years copper works better than other pure metals because of its hardness and malleability
Metallurgy other techniques include alloys – the heating and combination of two or metals to gain the benefits of both e.g. brass, bronze smelting – extracting pure metal from its ore e.g. getting iron from iron ore
Alchemy early experiments involving a combination of science and magic was mostly schemes for getting rich, or producing “miracle cures” such as anti- aging serums in the process, also resulted in: the discovery of mercury a method for the production of acids the improvement of glassware and lab equipment
Our understanding of the atom Accurately describing matter in terms of its atomic structure is something that scientists are still working on today. This section deals with the evolution of our ideas on the atom and its structure, from Aristotle (~400 BC) to today’s theory on Quantum Mechanics As we go through each scientist’s contribution, try to identify What was different about his view compared to previous theory? How did this view contribute to our current understanding?
Our understanding of the atom What you learn in Science 10 about the actual structure of the atom is still a simplification of what we believe to be true, however we will present the Bohr model as being “close enough”.
Our understanding of the atom Different elements are simply different combinations of the same three particles What makes oxygen different than nitrogen, for instance, is that oxygen has one more of each of the particles, but an oxygen proton looks exactly the same as a nitrogen particle.
Our understanding of the atom Features of this model of the atom: Protons (p+) Positively-charged particles Found in the nucleus Neutrons (n 0 ) Neutral particles Found in the nucleus Prevent the p+ from repelling each other
Our understanding of the atom Electrons (e-) tiny negatively- charged particles in orbit around the nucleus hardly have any mass (about 1/2000 th that of a p+ or n 0 ), but make up most of the volume of the atom How did we get to this understanding?
Aristotle400 B.C. all matter was composed of 4 elements: earth, air, water and fire what he got right: matter is made up of different combinations of elements elements can be divided up based on their properties what he got wrong: only 4 elements the elements were “continuous”, that is, they weren’t composed of “parts” DRYWET COLD HOT
Democritus400 B.C. working at the same time as Aristotle matter was made up of tiny particles, called atomos, that could not be divided into smaller pieces what he got right: matter is composed of tiny particles the atoms determine the properties of the element what he got wrong: atoms are indivisible, that is, that they aren’t made up of any smaller parts
John Dalton early 1800s performed experiments by combining different elements to form new substances (compounds) atoms are like small spheres that varied in size, mass or colour
John Dalton early 1800s what he got right: all matter is made of small particles called atoms all atoms of an element are identical in properties such as size and mass atoms of different elements have different properties atoms of different elements can combine to form compounds with new properties what he got wrong: atoms are solid and cannot be divided any further
J.J. Thomson1890s experimented with beams of particles produced in a vacuum tube he passed electricity through different samples of elements, and found that a beam of particles was emitted when the element became “excited” showed that the beam was made of negative charges, and that different elements produced the same type of beam thus credited with the discovery of the electron
J.J. Thomson1890s The “Plum Pudding” Model In Thomson’s model, the negatively charged electrons are stuck in a sphere of positive charge so named because it’s like raisins in plum pudding (or chocolate chips in a cookie)
J.J. Thomson1890s what he got right: atoms can be further divided into smaller particles one of those particles is the electron, which carries a negative charge the electrons in one element are the same as electrons in another element, but in different amounts
J.J. Thomson1890s what he got wrong: the electrons are stuck in the positive sphere, instead of around it this was corrected by Japanese Scientist H. Nagaoka in 1904, who said the electrons traveled around the nucleus like Saturn’s rings
Ernest Rutherford1890s begun his research with Thomson, but expanded on his ideas by discovering the nucleus his experiment is called the Gold Foil Experiment, and was so designed: a sample of a radioactive element was placed in a lead chamber with a tiny opening through this opening, a beam of positively-charged particles would be emitted these particles were traveling at a VERY high speed toward a thin sheet of gold foil
Ernest Rutherford1890s because the particles were moving so fast, and the gold was so thin, he expected the gold foil not to slow the particles down at all, and that they would pass through this would be like firing a cannonball at a sheet of tissue paper most of the time, this is exactly what happened, however… once in about every 10000 th time, the particle would bounce back this would be like the tissue deflecting the cannonball – a very surprising result!
Ernest Rutherford1890s from this experiment, he realized that the gold atoms had to be made mostly of empty space when the beam hit the 99.99% of empty space, it passed right through however, 0.01% of the time, the beam struck a positive “spot” on the gold foil, which he determined to be the tiny nucleus of the atom
Ernest Rutherford1890s what he got right: the nucleus is very small compared to the empty space around it the electrons occupy some of the empty space the nucleus has a positive charge what he got wrong: the electrons “swarmed” around the nucleus like bees around a beehive
Neils Bohrearly 1900s credited with discovering the orbital levels of the electrons, that is, that the electrons don’t swarm randomly, but rather occupy specific energy levels around the nucleus he discovered this by passing electricity through different elements to excite them, then letting the electrons release that energy in the form of light
Neils Bohrearly 1900s he then noted the pattern of light bands emitted from the element since the light emitted was related to the electrons, he reasoned that each element had a different number of electrons, and that the electrons occupied certain energy levels
Neils Bohrearly 1900s what he got right: electrons occupy set energy levels around the nucleus electrons cannot fall below the lowest energy level
Neils Bohrearly 1900s what he got wrong: electrons are not actually a solid particle, but actually a cloud of negative charge – Quantum Mechanical Model there are two types of particles in the nucleus: the proton and the neutron
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