Tool 1: Experimental Techniques (DP IB Biology)
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What is a hazard in a science experiment?
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What is a hazard in a science experiment?
A hazard is a feature of a procedure that may have inherently harmful properties, such as a chemical irritant or slippery rocks.
What is the difference between a hazard and a risk?
A hazard is something that can cause harm, while a risk is the level of danger posed by the hazard, considering likelihood and severity.
True or False?
Wearing a lab coat and goggles is enough to prevent all lab hazards.
False.
While wearing a lab coat and goggles is standard practice, specific safety precautions must be taken based on identified hazards.
True or False?
Disposal of toxic waste from laboratories will always result in environmental issues.
False.
Toxic chemical waste should be disposed of correctly, not down the laboratory sink. This will prevent or minimise environmental impact.
What does this hazard symbol indicate?
This symbol indicates that a substance is corrosive and so can cause skin burns and eye damage.
What is an ethical consideration when using animals in experiments?
Ethical considerations include minimising potential harm to animals, such as by keeping experiments short and handling animals minimally.
Why is it important that a Petri dish containing bacterial cultures is disposed of carefully and correctly in the laboratory?
Biological waste, such as Petri dishes with bacteria, should be disposed of correctly to prevent contamination and potential harm resulting from infection. This is an important safety consideration when working with bacteria.
True or False?
Informed consent is a safety consideration in human experiments.
False.
Informed consent means that individuals participating in an experiment are fully aware of the procedures and potential risks involved. This is an ethical consideration rather than a safety consideration.
What does this hazard symbol indicate?
This hazard symbol indicates that a substance is hazardous to the environment.
What are examples of units of mass that can be used in scientific experiments?
Units of mass that are used in scientific investigation include:
kilograms (kg)
grams (g)
milligrams (mg)
How should a digital balance be prepared before use?
A digital balance must be set to zero before use to ensure accurate mass measurements.
True or False?
A measuring cylinder is the most accurate apparatus for measuring a fixed volume of liquid.
False.
Measuring cylinders are used when accuracy is not an important factor.
A volumetric pipette is the most accurate apparatus for measuring a fixed volume of liquid.
Define the term meniscus in the context of measuring liquids.
The meniscus is the curve seen at the liquid's surface when measuring its volume in a container, such as a graduated cylinder or pipette. The bottom of the meniscus should be used when determining volume.
What is a gas syringe used for in experiments?
A gas syringe is used to measure the volume of gas produced in a reaction.
In the investigation below, suggest why a gas cylinder should be used to measure the product produced, rather than counting the bubbles.
A gas syringe should be used in the investigation shown because it is a more accurate way of measuring the volume of gas produced.
Counting the bubbles does not allow for bubbles of different sizes and can also result in errors if bubbles are missed during the counting process.
How can time be measured during a lab investigation?
Time can be measured using a stopwatch. It can be recorded in minutes (min) or seconds (s).
True or False?
Digital temperature probes are less precise than traditional thermometers.
False.
Digital temperature probes are often more precise than traditional thermometers, reading to 0.1 °C.
What are examples of units of length that are used in scientific measurements?
Units of length used in scientific measurement include:
metre (m)
centimetre (cm)
millimetre (mm)
micrometre (μm)
nanometre (nm)
What are methods that can be used to take a cell count in microbiology?
Examples of cell count methods include:
direct counting using a hemocytometer or a counting chamber
streak plating with a known volume of cell culture
In ecological studies, why is it common to take samples of the larger population rather than recording actual counts?
Taking actual counts in ecological studies can be time-consuming and inefficient. Ecologists take representative samples which can be scaled up to give estimates of an overall population.
State two rules that should be applied when producing a biological drawing.
When producing a biological drawing, you should ensure that you follow the conventions below:
use a sharp pencil
draw clear, single lines with no sketching or shading
only draw structures that are visible
apply correct proportions
ensure the drawing fills the space given
label drawings with straight lines that do not cross or have arrowheads
give the drawing a title
What is the purpose of paper or thin-layer chromatography?
The purpose of paper or thin layer chromatography is to separate and identify components of a mixture.
What is colorimetry?
Colorimetry is a technique used to measure the concentration of a solution by assessing its colour intensity.
A colorimeter will measure the light absorbance or transmission through a solution to provide a quantitative reading of colour intensity.
True or False?
Serial dilutions are used to create a gradient of concentrations.
True.
Serial dilutions are used to create a gradient of concentrations by systematically reducing the concentration of a solution.
What does physical and digital molecular modelling involve?
Physical and digital molecular modelling involved building models of molecules, either using modelling kits (physical) or computer programmes (digital). This allows molecule structure to be visualised.
What is a light microscope?
A light microscope is an instrument that uses visible light to magnify specimens.
What is an eyepiece graticule?
An eyepiece graticule is a small disc with an engraved scale within the eyepiece of a light microscope. It acts as a ruler in the field of view.
What does the preparation of temporary mounts involve?
The preparation of temporary mounts involves:
placing a specimen on a slide
adding a drop of liquid and/or stain
covering it with a cover slip
What is systematic sampling?
Systematic sampling is a method of sampling where a sample is taken at regular, pre-determined intervals.
What is karyotyping?
Karyotyping is the process of arranging and analysing the chromosomes of an organism.
What can be determined during cladogram analysis?
Cladogram analysis can be used to determine evolutionary relationships between organisms, e.g. how recently species diverged from a common ancestor.