Experimental Techniques (Cambridge (CIE) IGCSE Combined Science: Chemistry): Flashcards
Exam code: 0653
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Define the term burette.
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Cards in this collection (19)
Define the term burette.
A burette is a piece of apparatus used to measure a variable volume of liquid between 0 cm3 and 50 cm3. It is the most accurate way to measure variable volumes and is read from top to bottom (0.00 cm3 at the top).
Why is a gas syringe preferred over downward displacement of water for collecting gas?
A gas syringe is preferred because it is more precise and accurate. Downward displacement of water cannot be used if the gas is soluble in water, which would give an inaccurate volume reading.
A volumetric pipette measures a .......... volume of liquid and is matched to the bottom of the .......... to make the measurement.
A volumetric pipette measures a fixed volume of liquid and is matched to the bottom of the meniscus to make the measurement.
True or False?
A digital balance should be tared before use.
True.
Taring sets the balance to zero before use, ensuring the mass reading reflects only the substance being weighed and not the container.
What is the correct unit of temperature in chemistry experiments?
Temperature is measured in degrees Celsius (°C). Laboratory thermometers typically have a precision of 0.5 °C or 1 °C, while digital temperature probes can read to 0.1 °C.
Define downward displacement of water as a gas collection method.
Downward displacement of water is a method of collecting gas where an inverted measuring cylinder filled with water captures the gas produced. It cannot be used for gases that are soluble in water.
Measuring cylinders are used when .......... volumes are required, they are .......... so they have a scale.
Measuring cylinders are used when approximate volumes are required; they are graduated so they have a scale.
True or False?
A stopwatch display reading 1:30 should be recorded as 1.30 minutes.
False.
A display of 1:30 means 1 minute and 30 seconds, which is 1.5 minutes or 90 seconds. Recording it as 1.30 minutes is a common error.
Which piece of apparatus is most accurate for measuring a variable volume of liquid?
A burette is the most accurate apparatus for measuring a variable volume of liquid. It reads from 0.00 cm3 at the top to 50 cm3 at the bottom and is most commonly used in titrations.
Why is the pencil line kept above the solvent level at the start of a chromatography experiment involving liquid volume measurement?
The pencil line must be above the solvent level so that the sample spots do not dissolve directly into the solvent. This ensures the solvent carries the substances up the paper by capillary action rather than washing them away.
Define the term solvent.
A solvent is the liquid in which a solute dissolves to form a solution. For example, water is the solvent in seawater.
Define the term solute.
A solute is the substance that dissolves in a solvent to form a solution. For example, salt is the solute in seawater.
True or False?
A saturated solution can dissolve more solute at the same temperature.
False.
A saturated solution already contains the maximum concentration of solute dissolved in the solvent at that temperature. No more solute will dissolve unless the temperature is changed.
A solution is a mixture of one or more .......... dissolved in a solvent; the substance left behind after filtration is called the .......... .
A solution is a mixture of one or more solutes dissolved in a solvent; the substance left behind after filtration is called the residue.
What is the difference between the filtrate and the residue in a filtration?
The filtrate is the liquid or solution that passes through the filter paper. The residue is the solid that remains on the filter paper and does not pass through.
Define the term saturated solution.
A saturated solution is a solution containing the maximum concentration of solute dissolved in the solvent at a specified temperature. Adding more solute will not cause further dissolution.
Why does a substance described as insoluble not form a solution?
An insoluble substance will not dissolve in a given solvent. Its particles do not break apart and mix evenly with the solvent particles, so no solution is formed. For example, sand is insoluble in water.
True or False?
The filtrate is always a pure substance.
False.
The filtrate is the liquid or solution that passes through the filter. It may still contain dissolved substances and is not necessarily pure — it is only free of undissolved solids.
In seawater, water is the .......... and salt is the .......... which together form a .......... .
In seawater, water is the solvent and salt is the solute which together form a solution.
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