practical skills Flashcards
What is an independent variable? (2)
The variable that is changed in an experiment;
To test its effects on the dependent variable
What is a dependent variable? (2)
The variable that is measured in an experiment;
This variable is affected by the independent variable
What are controlled variables? (2)
Factors that are kept constant during an experiment;
That ensures that any changes in the dependent variable are due to the independent variable only
What is the mean of a data set? (2)
A measure of average;
The sum of all values divided by the number of values in the data set
What are qualitative observations? (2)
Observations that deal with descriptions; E.g. colours
What are quantitative observations? (1)
Numerical values
What is accuracy? (2)
How close a reading is to the true value;
A value is considered accurate if it is close to the true result
How do you interpret volumes? (2)
When reading volume from a measuring cylinder or syringe;
Take where the meniscus is
How do you reduce random errors in measurements? (3)
Taking multiple measurements and calculating an average;
Using more precise instruments;
Increasing sample size
What is the uncertainty in a measurement? (2)
The range within which the true value is expected to lie;
Given by the precision of the instrument used and the repeatability of the measurements
How do you calculate the percentage uncertainty of a measurement? (2)
(Absolute uncertainty / Measurement value) x 100
What should you include when drawing a graph in an experiment? (4)
Labelled axes (with units);
Title;
Line of best fit;
Data points plotted (with error bars if applicable)
What is the purpose of a control experiment? (3)
Used to compare results and confirm that the effect on the dependent variable;
Is due to the independent variable alone;
Without the interference from other factors
How do you ensure an experiment is reliable? (3)
Repeat the experiment multiple times;
Maintain consistent controlled variables;
Use precise instruments
What are systematic errors? (2)
Consistent, repeatable errors
Caused by faulty equipment or flawed experimental design
How can systematic errors be minimised? (3)
Calibrating instruments; Using appropriate methods;
Cross-checking results with different methods
Why is it important to calibrate instruments before taking measurements? (3)
Ensures that the instruments provide accurate readings;
By comparing them to a known standard;
Reducing systematic errors
What is a colorimeter? (2)
Apparatus that measures light absorbance or light transmission;
Used to measure colour change
What questions are asked in a risk assessment? (3)
What could harm you?;
What harm could it cause you?; What actions could be put in place to prevent / treat harm?
What are some ways in which pH is measured? (3)
Indicator paper;
Indicator solution;
pH metre
How is length measured? (2)
Ruler; Tape measure
What needs to be considered when measuring length? (2)
The scale;
To ensure there is a high enough precision of equipment
How is temperature measured? (2)
Thermometer;
Data logger
How is volume of a gas measured? (1)
Gas syringe
