Aim 3: How do we use lab equipment to make observations and take measurements?
DO NOW: Answer the following questions 1. What is the purpose of using laboratory tools and equipment? - Makes experiments more accurate and precise - Makes experimentation safer - Makes observations easier
DO NOW: Answer the following questions 2. Why is it important that we use these tools properly? - Ensures lab safety - Ensure that we have accurate and precise results - If we learn to use lab equipment correctly, scientists should be able to obtain the same results when they repeat the experiment
Why is it important that all countries use the metric system? Metric system history Devised by a group of French scientists to create a system of standard measurements (Centimeter, meter, kilogram, millimeter, milliliter etc) Different from what we usually use (Inches, feet, pounds, gallon etc) Why is it important that all countries use the metric system?
Practice
I. LENGTH What instrument is most commonly used to measure length? _________________ What does cm stand for? ________________ How many reference marks make up one cm? ______ What are these reference marks called? ____________________ Therefore there are ____________________ in one centimeter MILLIMETERS 10 MILLIMETERS
d) Answer the following questions:
d) Answer the following questions:
d) Answer the following questions: 9 90mm/10 = 9 cm
II. VOLUME What instrument is most commonly used to measure volume? ______________________________ What unit should answers be expressed in? ________________ What is the abbreviation? _______ What is the curved surfacve of a liquid called? ______________________ GRADUATED CYLINDER MILLILITERS mL MENISCUS
*ALWAYS KEEP IT ON A FLAT SURFACE! d) What is the proper way to read a volume of a liquid? ___________________________________________ ___________________________________________ KEEP GRADUATED CYLINDER FLAT ON THE SURFACE AND READ THE BOTTOM OF THE MENISCUS AT EYE LEVEL *ALWAYS KEEP IT ON A FLAT SURFACE!
e) Answer the following questions:
e) Answer the following questions:
III. TEMPERATURE What instrument is most commonly used to measure temperature? ______________________________ What unit should answers be expressed in? ___________________ What is the abbreviation? _______ What other scale can temperature be expressed in? _______________________________________
d) Why should you NOT hold the thermometer in your hand when taking a reading? e) Similarly, when taking a temperature reading of a liquid, why should the thermometer not touch either sides or bottom of the container? Our hand can transfer heat/cold to the thermometer which will not give us a true reading of the liquid We want the temperature of the water not the beaker. This could change our observations and results
f) Read the following temperature scales and report your answers to the nearest tenth of a degree. 13 98.3 - .7
IV. MASS What instrument is most commonly used to measure mass? ______________________________ What unit should answers be expressed in? ___________________ What is the abbreviation? _______
c) Calculate the mass for each triple beam balance below 37.3 g
c) Calculate the mass for each triple beam balance below 536.8 g
V. What is the difference between accuracy and precision? How close a measurement is to the real value/accepted value (proper equipment) How close a series of measurements are to one another (good technique)
V. How come all measurements have some level of inaccuracy and uncertainty? There will always be errors due to the experimenter, the equipment and changes in experimental conditions. I give you a graduated cylinder. You say it’s 41.1 ml, I say it’s 41.5, you say 42. Why is that? All measurements are rounded up. Some may measure more precise than others which is why it’s important to repeat experiments *This is why it is important that we repeat measurements and experiments MORE THAN ONCE!
VI. How do laboratory tools improve the observations made by a scientist? It increases the accuracy, makes observations easier and allows experiments to be easily repeated. Can you observe a cell with the naked eye? You need a microscope. I want to see a specific organelle of the cell, so I will stain it. How can you heat up a liquid without a bunsen burner?