Experimental Design Notes PDF - Catholic High School - Level 3 Chemistry
Document Details
![GoldenEvergreenForest8111](https://quizgecko.com/images/avatars/avatar-3.webp)
Uploaded by GoldenEvergreenForest8111
Catholic High School
Tags
Summary
This document contains lesson notes for Level 3 Chemistry, focusing on experimental design. It covers learning outcomes related to apparatus, measurement, and gas collection techniques. The notes are from Catholic High School and include information on precision, accuracy, and drying gases.
Full Transcript
Level 3/ Experimental Design Teacher’s Copy Chemistry Catholic High School Level 3 Chemistry...
Level 3/ Experimental Design Teacher’s Copy Chemistry Catholic High School Level 3 Chemistry Lesson Notes 1 – Experimental Design Name: Learning Outcomes (a) Name appropriate apparatus for the measurement of time, temperature, mass and volume, including burettes, pipettes, measuring cylinders and gas syringes. (b) Suggest suitable apparatus, given relevant information, for a variety of simple experiments, including drying and collection of gases and measurement of rates of reaction (drying agents will be limited to calcium oxide, concentrated sulfuric acid and fused calcium chloride) http://www.thecomicstrips.com/store/add.php?iid=126141 R ack-your-brains What is measurement all about? Why do we have to choose appropriate apparatus for our measurements? What is the difference between precision and accuracy? Match the following diagrams with the degree of accuracy and precision: High accuracy Low accuracy High accuracy Low accuracy High precision High precision Low precision Low precision Low accuracy Low accuracy High accuracy High accuracy Low precision High precision Low precision High precision Last updated by: SA (Dec 2024) 1 Level 3/ Experimental Design Teacher’s Copy Chemistry 1. Measurement of Physical Quantities The modern metric system used to measure quantities of different things is called the International System of Units (S.I. Units). Scientists use S.I. units as a common standard for their measurements for ease of communication. Physical S.I. unit Units of Apparatus Smallest Values can be Examples of Quantities recordings division of recorded to the recording instrument nearest… Mass kilogram (kg) gram (g) electronic balance 0.01 g 0.01 g 5.10 g, 5.11 g kilogram (kg) 1 kg = 1000 g tonne (t) 1 t = 1000 kg Time second (s) minute (min) digital stopwatch 0.01 s 1s* 20 s, 28 s 1 min = 60 s hour (h) 1 h = 60 min Temperature kelvin (K) degree Celsius Thermometer 1 oC 0.5 oC 22.0 oC, 22.5 oC (°C) (-10 oC to 110 oC) Temperature in K = Temp in°C + 273 Note: Data-logger with temperature sensor (can record data continuously over time) * Depending on the experiment, the recording of measured time may be to the nearest 0.1 s or the nearest 1 s, even though a typical digital stopwatch has a resolution of 0.01 s. This is to account for uncertainty due to human reaction time. Last updated by: SA (Dec 2024) 2 Level 3/ Experimental Design Teacher’s Copy Chemistry Physical S.I. unit Units of Apparatus Quantities recordings Volume cubic metre (m3) cubic centimetre The apparatus we choose for an (cm3) experiment depends on 1 m3 = 1000 dm3 cubic decimetre - the volume to be measured and (dm3) - the precision of measurements of volume (see next section) 1 dm3 = 1000 cm3 Measuring volume of liquids Beaker Measuring Burette Pipette (100 cm3) Cylinder (50.00 cm3) (25.0 cm3) (100 cm3) Apparatus measures approximate measures fixed volumes only volumes only Smallest division of 25 cm3 1 cm3 0.1 cm3 instrument Values can be recorded 0.5 cm3 0.05 cm3 to the nearest… Examples of 14.0 cm3, 24.00 cm3, recording 14.5 cm3 22.05 cm3 Last updated by: SA (Dec 2024) 3 Level 3/ Experimental Design Teacher’s Copy Chemistry When a liquid or a solution is placed in a container, it forms a curved surface called a meniscus. The figure below shows how to take reading of the meniscus in a burette. Read the scale at the top of the convex Read the scale at the bottom of the meniscus for liquids such as mercury. concave meniscus (most common). 2. Methods of Gas Collection The method to collect a gas depends on its physical properties, namely: Solubility — how soluble a gas is in water Density — how dense the gas is compared to air. As a general guide, relative mass of air is taken to be about 30. The best method to use would be one that allows you to collect the largest volume of gas possible. 1 2 3 4 Downward delivery Upward delivery Water displacement Gas syringe Collects gases which Collects gases which Collects gases which Collects most gases are soluble in water are soluble in water are insoluble or and measures their and denser than air and less dense than slightly soluble in volumes air. water. Examples: chlorine Example: ammonia, Example: hydrogen, and hydrogen hydrogen and helium oxygen and carbon chloride dioxide Last updated by: SA (Dec 2024) 4 Level 3/ Experimental Design Teacher’s Copy Chemistry The table below shows some common gases and their properties. Nature Solubility in Molecular Gas Density relative to air of gas water Mass Hydrogen (H2) Neutral Insoluble 2 Less dense than air Oxygen (O2) Neutral Slightly soluble 32 About the same Nitrogen (N2) Neutral Insoluble 28 About the same Carbon monoxide (CO) Neutral Insoluble 28 Slightly less dense than air Carbon Dioxide (CO2) Acidic Slightly soluble 44 Denser than air Chlorine (Cl2) Acidic Soluble 71 Denser than air Hydrogen Chloride (HCl) Acidic Very Soluble 36.5 Denser than air Sulfur Dioxide (SO2) Acidic Very Soluble 64 Denser than air Ammonia (NH3) Alkaline Very Soluble 17 Less dense than air Acidic Very Soluble 32+3(16)= Denser than air Sulfur trioxide (SO3) 80 3. Drying Gases Sometimes we need to collect a dry gas in an experiment. We can dry a gas by passing it through a suitable drying agent. Drying Agent Concentrated sulfuric Quicklime Fused calcium chloride acid (calcium oxide) Nature acidic alkaline neutral Diagram Concentrated sulfuric acid quicklime Note the position of the delivery tubes Fused calcium chloride Remarks Used to dry gases except Used mainly to dry Used to dry most gases for alkaline gases such as ammonia gas. except for ammonia. ammonia. Reason Acidic drying agents like Alkaline drying agents like Calcium chloride will react concentrated sulfuric acid calcium oxide should not with ammonia gas. should not be used to dry be used to dry acidic alkaline ammonia gas. gases like chlorine, They will neutralise each hydrogen chloride, carbon other. dioxide and sulfur dioxide. Neutralisation will occur. Last updated by: SA (Dec 2024) 5 Level 3/ Experimental Design Teacher’s Copy Chemistry For example, in the figure below, a gas which is less dense than air is produced from a reaction in a conical flask. The gas is then passed through a drying agent (fused calcium chloride) before being collected by the upward delivery method. Gas collected Fused calcium chloride Checkpoint 1 1. Draw an experimental setup to collect a dry sample of ammonia gas from the reaction between dilute sodium hydroxide and ammonium sulfate. Name the drying agent used. Last updated by: SA (Dec 2024) 6 Level 3/ Experimental Design Teacher’s Copy Chemistry 2. The diagram shows the apparatus used to obtain carbon monoxide using three chemical reactions. reaction 1: dilute hydrochloric acid + calcium carbonate → carbon dioxide + calcium chloride + water reaction 2: charcoal (carbon) + carbon dioxide → carbon monoxide reaction 3: unreacted carbon dioxide + dilute sodium hydroxide → sodium carbonate + water dilute sodium hydroxide (a) Explain if the carbon monoxide gas obtained at the end would be (i) dry; and (ii) pure. Last updated by: SA (Dec 2024) 7