2. Experimental Techniques (for WA1)

Paper Chromatography + Collection and drying of gases

two or more elements chemically combined in a fixed composition

compounds

two or more substances physically mixed together in any proportion

mixtures

components of a ________ can be seperated by physical means

mixture

can only be broken down into its elements or its simpler compounds by chemical processes

compounds

the chemical properties of a _______ are the same as those of its components

mixtures

physical and chemical properties of a ______ are different from its constituent elements

compounds

methods to determine purity: b________ ________ ___________, __________ ________ _________, ________ __________

boiling point determination, melting point determination, paper chromatography

importance of measuring purity: ensures that only _________ substances are used esp in the food industry

permitted

importance of measuring purity: presence of _________ can have ______ effects in a ______ / _________

impurities, harmful, drug, medicine

importance of measuring purity: presence of _________ can _____ with _______ pure substances are involved

impurities interfere reactions

purity: for example the addition of salt to water ________ its boiling point but the addition of salt to water ________ its freezing point

raises lowers

purity: the ________ the amount of ________, the larger the change in melting or boiling points

greater impurities

a pure substance has a ________ meling and/or boiling point under fixed conditions

fixed

chromatography:____________ ________ may be used to reveal some colourless substances e.g. conjugated systems

ultraviolet light

locating agent is a _______ that can ____ with ________ substances in order to make them _______

chemical react colourless visible

retention factor is the ratio between the ________ _________ by the _________ and the ________ ________ by the ________

distance travelled substance distance travelled solvent

methods of paper chromatography: ________ method is faster due to the effect of _________

descending gravity

chromatography: ________ ______ should be near the ____ of the paper to ensure that the dyes are ________ separated

solvent line top fully

paper chromatography: ______ of solution and dyes on the starting line should be _______ and ________ to ensure that the dyes are _________ __________

spots small concentrated distinctly separated

chromatography: the more soluble the substance, the ______ and _______ it travels

further faster

chromatography is used to _______ and _______ _______ amounts of substances that are ________ in _______.

seperate identify small dissolved solvents

chromatography: why does the container need to be closed with a lid? (to __________ ________ _______ and _______ ___ ________ ________ is ________)

to minimise solvent evaporation and drying up before process is completed

chromatography: will the results of the experiment be the same if a different solvent is used? (the result will be _______ as the ______ have _________ ________ in _________ _________)

the result will be different as the solutes have different solubilities in different solvents

chromatography: why should the start line be above the solvent level? (So that the _______ will ____ __________ in the ________ _______ the _________ in the _____ can be ___________)

so that the sample will not dissolve in the solvent before the components in the sample can be seperated

chromatography: why should the spots and dyes on the starting line be small? (to _______ that there will _____ be any __________ of the _________)

to ensure that there will not be any overlapping of the components

paper chromatography: why should the solvent front be near the end of the paper at the end of the experiment? (to ________ _________ _________ of the _________ in the _______)

to ensure maximum seperation of the components in the sample

chromatography: how can chromatograpy be applied to colourless substances? (use a ________ _______)

use a locating agent

chromatography: what are the advantages of using chromatography (over other seperation techniques)? (only a _____ amount of _______ is _______. _________ to __ __ and ______, in the case of ______ _____________)

only a small amount of sample is required. inexpensive to set up and conduct, in the case of paper chromatography

paper chromatography: why should the base line be drawn using a pencil instead of a pen? (the _______ will ____ _________ the _______ _____, unlike ____ which contains _______ _____. the _________ ______ from the ____ will ________, thus ________ with _____ from the test sample)

the solvent will not seperate the pencil mark, unlike ink which contain soluble dyes. the seperated dyes from the ink will smudge, thus interfering with dyes from the test sample

how does the two solutes separate from each other in chromatography? (A _____ that is ____ _______ in the solvent will travel up the filter paper a ________ distance than a solute that is _____ _________ in the solvent)

a solute that is more soluble in the solvent will travel up the filter paper a greater distance than a solute that is less soluble in the solvent

how does chromatography works? (the ________ solutes in the _____ have _________ solubilities in the _____ solvent)

the different solutes in the mixture have different solubilities in the same solvent

why should spots be above the solvent in chromatography? (to _______ the spots from being _________ from the paper)

to prevent the spots from being removed from the paper

why is an ink pen not used as the ink for chromatography?

ink is a mixture which can dissolve in certain solvents and spread up the chromatogram

what is sprayed on the chromatogram to make the colourless spots visible? (2 words)

locating agent

separate substances with different solubility

chromatography

The method to collect a gas from a preparation depends on two factors: (_ of the _ in _, _ of the _ as compared to _)

solubility of the gas in water, density of the gas as compared to air

method for gases that are insoluble or have low solubility in water

displacement of water

what gases can be collected using displacement of water

carbon dioxide hydrogen oxygen

use displacement of water for gases that are _ or have _ _ in _

insoluble low solubility water

what method is this

displacement of water

method for gases that are more dense than air

downward delivery

what gases can be collected using downward delivery

chlorine hydrogen chloride gas

use downward delivery for gases that are _ _ than _

more dense air

what method is this

downward delivery

method for gases that are less dense than air

upward delivery

what gases can be collected using upward delivery

ammonia gas hydrogen gas

use upward delivery for gases that are _ _ than _

less dense air

what method is this

upward delivery

gas can also be collected and measured using a _ _

gas syringe

What do you think is the purpose of this set up? Which apparatus is essential for this purpose? (_ the _ of a _ by _ the decrease in _ _ _. _ is an essential apparatus for investigating experiments involving _.)

Measure the rate of a reaction by determining the decrease in mass over time. Stopwatch is an essential apparatus for investigating experiments involving rate.

Can i use a beaker to measure the same volume of solution? (_ a beaker is _ _ for any _ of _ as it is _ an _ instrument.)

No a beaker is not used for any measurement of solutions as it is not an accurate instrument.

What do you think is the purpose of this set up? Is there another way to achieve this purpose? (_ and _ _ of gas. A _ _ can be used for measuring the _ of a gas _.)

Collect and measure volume of gas. A gas syringe can be used for measuring the volume of a gas accurately.

What do you think is the purpose of this set up? Is there another way to achieve this purpose? (_ and _ _ of gas. _ _ _ method is another way to _ the _ of gas produced if the gas is _ in _.)

Collect and measure volume of gas. Displacement of water method is another way to measure the volume of gas produced if the gas is insoluble in water.

Can I use a beaker to dispense the liquid instead of apparatus '5.'? (No a beaker _ _ _ as it cannot _ the _ of a liquid _ .)

No a beaker cannot dispense liquid as it cannot measure the volume of a liquid accurately.

Can I use a measuring cylinder to measure out the 25.0cm^3 instead? (_ the measuring cyclinder is _ _ than a _.)

No the measuring cylinder is less accurate than a pipette.

We can dry a gas by passing it through a _ _ in appropriate apparatus.

drying agent

_ is used to dry acidic gases such as chlorine and hydrogen chloride.

concentrated sulfuric acid

concentrated sulfuric acid is used to dry _ gases such as _ and _ _.

acidic chlorine hydrogen chloride

concentrated sulfuric acid cannot be used to dry _ gases as it _ with them.

alkaline reacts

_ is used to dry alkaline gases such as ammonia gas

quicklime (calcium oxide)

quicklime (calcium oxide) is used to dry _ gases such as _ gas

alkaline ammonia

quicklime (calcium oxide) cannot be used to dry gases as it with them.

acidic reacts

_ can be used to dry most gases such as hydrogen

fused calcium chloride

fused calcium chloride can be used to dry _ gases such as _.

most hydrogen

fused calcium chloride cannot be used to dry _ gas

ammonia

what drying agent

concentrated sulfuric acid

what drying agent

quicklime

what drying agent

fused calcium chloride

what apparatus is used to measure time?

stopwatch

what apparatus is used to measure temperature?

thermometer

what apparatus is used to measure mass?

electronic balance

what apparatus (most accurate) is used to measure volume of solution or liquid?

burette

what apparatus is used to measure volume of solution or liquid more accurate than measuring cylinder?

pipette

what apparatus (least accurate) is used to measure volume of solution or liquid?

measuring cylinder

what apparatus is used to measure volume of gas?

gas syringe

precision of thermometer including units

0.5'C

precision of electronic balance including units (record what we see) ________ or ______

0.01g or 0.001g

precision of stopwatch including units (record what is asked by qn)

0.01s

precision of measuring cylinder including units (half of smallest division)

0.5cm3

precision of pipette including units

25.0cm3

precision of burette including units

0.05cm3

precision of gas syringe including units

0.5cm3

solubility in water of ammonia

high

solubility in water of hydrogen chloride

high

solubility in water of sulfur dioxide

high

solubility in water of chlorine

high

solubility in water of carbon dioxide

low

solubility in water of carbon monoxide

low

solubility in water of oxygen

low

solubility in water of hydrogen

insoluble

solubility in water of helium

insoluble

solubility in water of nitrogen

insoluble

acidity/basicity of ammonia

basic

acidity/basicity of hydrogen chloride

acidic

acidity/basicity of sulfur dioxide

acidic

acidity/basicity of chlorine

acidic

acidity/basicity of carbon dioxide

acidic

acidity/basicity of carbon monoxide

neutral

acidity/basicity of oxygen

neutral

acidity/basicity of hydrogen

neutral