Required Practicals
What's covered
Key facts
Electrolysis
At the anode (positive electrode), ions lose electrons — this is called oxidation.
Hooke's Law
Beyond the elastic limit, a spring is permanently (plastically) deformed and does not return to its original length.
I-V characteristics
A diode allows current to flow in one direction only (forward bias); in reverse bias it has very high resistance and almost no current flows.
Microbiology — antiseptics and antibiotics
Aseptic technique is a set of methods used to prevent contamination of cultures by unwanted microorganisms.
Microscopy
Actual size = image size ÷ magnification; a 4 mm image at ×400 represents an actual size of 0.01 mm.
Specific heat capacity
ΔE = mcΔθ, where ΔE is energy (J), m is mass (kg), c is specific heat capacity (J/kg°C), Δθ is temperature change (°C).
Titration
Burette volumes are read at eye level from the bottom of the meniscus, to the nearest 0.05 cm³, to avoid parallax error.
Electrolysis
During electrolysis at the cathode, positive ions (cations) gain electrons and are reduced.
Hooke's Law
Hooke's Law: F = ke, where F is force (N), k is the spring constant (N/m), and e is the extension (m).
I-V characteristics
A filament lamp's resistance rises as the filament heats up, which is why its I-V graph is not a straight line.
Sample questions
A taste of the 100 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What happens at the cathode during electrolysis?
- •Negative ions are attracted and gain electrons
- •Oxidation — negative ions lose electrons
- •Positive ions are repelled away from the electrode
- ✓Reduction — positive ions gain electrons to form atoms
What does Benedict's reagent test for?
- •lipids (fats and oils)
- •proteins
- ✓reducing sugars
- •starch
State Hooke's Law.
- •Extension increases by a constant amount for each unit of force
- ✓Extension is directly proportional to force, up to the limit of proportionality
- •Force and extension are inversely proportional at all loads
- •Force is directly proportional to the square of the extension
What does an I-V characteristics practical investigate?
- •charge vs time relationship
- ✓current vs voltage relationship
- •power vs current relationship
- •resistance vs temperature relationship
What is the first step when making a pure salt from an acid and an insoluble metal oxide?
- ✓Add excess solid metal oxide to the acid until no more dissolves
- •Add the acid to the solid until the solid disappears
- •Add water to dilute the acid before adding the solid
- •Heat the acid until it evaporates
What is aseptic technique?
- •identifies the type of bacteria present
- •kills all bacteria on an agar plate
- •measures the growth rate of bacteria
- ✓prevents contamination of cultures
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