1.1 Practical Skills

Question 1

Define variable.

Answer 1

A quantity that has the potential to change and can affect the outcome of an experiment

Question 2

Define independent variable.

Answer 2

The thing you change to see the effect t has on one other factor

Question 3

Define dependant variable.

Answer 3

The thin that you observe in the experiment.

Question 4

What are the three different types of data?

Answer 4

Discrete, continuous and categoric.

Question 5

How do you obtain continuous data?

Answer 5

Any value on a scale - can never measure the exact value.

Question 6

How do you obtain categoric data?

Answer 6

Values that can be sorted into categories - eg blue green and red.

Question 7

Where do you read the volume of a liquid from?

Answer 7

The bottom of the meniscus.

Question 8

How do you make it easier to measure colour change?

Answer 8

White background.

Question 9

How do you make it easier to see a precipitate?

Answer 9

Mark and x on a piece of paper and put in under the reaction contained - it is cloudy when you can no longer see the x.

Question 10

What are valid results?

Answer 10

Results that answer the original question - if you haven’t controlled all variables BC not testing what you wanted.

Question 11

What are accurate results?

Answer 11

Results that are really close to the true value.

Question 12

What are precise results?

Answer 12

Results that can be independently reproduced in independent experiment s.

Question 13

Define valid

Answer 13

A valid expediency provides information to test the aim of the experiment

Question 14

What is a hypothesis?

Answer 14

A prediction and explanation of the chemistry behind the prediction

Question 15

What’s an experiment?

Answer 15

An ordered see of practical steps used to test the hypothesis

Question 16

What is resolution

Answer 16

The smallest change in the quantity being measured that can be observed

Question 17

What is accuracy?

Answer 17

How close to the true value a measurement is

Question 18

What is the control variable?

Answer 18

The actor theta you must keep contacts between experimental runs so you can compare results

Question 19

What is an extraneous variable?

Answer 19

A factor that is not controlled or measure in the experiment but may introduce error into the results

Question 20

What is a plan?

Answer 20

A summary of an experiment that you wish to complete

Question 21

What is a method?

Answer 21

A step by step detailed explanation of how to complete an experiment

Question 22

How to measure mass

Answer 22

weigh full and empty

Question 23

How to measure solutions

Answer 23

volumetric pipette from bottom of meniscus

Question 24

How to measure gas

Answer 24

• gas syringe

- over water - fill measuring cylinder and measure water displaced

Question 25

Preparing standard solution

Answer 25

- dissolve solid in beaker (approx 100ml water) - pour into volumetric flask using funnel - rinse beaker - pour into volumetric flask - fill so bottom of meniscus is on the line

Question 26

Titration

Answer 26

- measure 25cm3 of standard solution using volumetric pipette - add to conical flask with 2-3 drops of indicator - fill burette with unknown conc - add this to conical flask - while over white tile until permanent colour change - record volume added to 2dp (either 0.00 or 0.05) - repeat adding drop by drop until end poinit - repeat until concordant results

Question 27

What are concordant results?

Answer 27

within 0.1

Question 28

Test for carbonate

Answer 28

add strong dilute acid collect gas and pass through limewater positive = fizzing and limewater cloudy

Question 29

Test for sulphate

Answer 29

dilute hydrochloric acid and then barium chloride | white precipitate of barium sulfate produced

Question 30

Test for halide

Answer 30

- dissolve halide in water - silver nitrate and dilute nitric acid - ppt colour - dilute then conc ammonia - note solubility

Question 31

Test for ammonium ions

Answer 31

- add sodium hydroxide and warm gently - test gas with red litmus - turns blue

Question 32

What happens when metal ions react with ammonia or hydroxide ions?

Answer 32

insoluble coloured compounds

Question 33

Method for testing for metal ions

Answer 33

- fill half a test tube with sample - add aqueous ammonia or NaOH dropwise - note colour of ppt

Question 34

What transition metal is it if a blue ppt is formed?

Answer 34

Cu2+

Question 35

What transition metal is it if a brown ppt is formed?

Answer 35

Mn2+or Fe2+

Question 36

What transition metal is it if a green ppt is formed?

Answer 36

Fe2+ ot Cr3+ (green-grey)

Question 37

Testing enthalpy change of combustion

Answer 37

weigh fuel, burn it to heat a know amount of water, measure temp change, reweigh fuel use q=mc delta t and change in H =-q/n where q=energy change

Question 38

Determining enthalpy change of neutralisation

Answer 38

measure out known conc of acid and alkali measure temp change use q=mc delta t for TOTAL volume use delta H = -q/n for limiting reactant

Question 39

Determining enthalpy change of reaction

Answer 39

- dissolve salt in water - measure enthalpy change - dissolve hydrated salt in water - measure enthalpy change - q= mcdeltat - find enthalpy change of forming hydrated salt from salt and water

Question 40

How can you measure rate of reaction?

Answer 40

-loss in mass -volume of gas produced -amount of light passing through over time plot graph and find gradient

Question 41

How do you determine initial rate?

Answer 41

- make solution of known concentration - react and measure initial rate - change conc but keep volume same - react and measure initial rate - compare difference

Question 42

Quickfit for reflux

Answer 42

- vertical condenser attached to flask - water goes in bottom of condenser - often use water bath or heating element to heat flask rather than bunsen burner as chemicals may be flammable

Question 43

Quickfit for distillation

Answer 43

- condenser at angle (higher end at flask and sloping away) - water attached at lower end - -thermometer level with entrance to condenser

Question 44

Purification of organic liquid

Answer 44

separating funnel to remove organic layer from aqueous layer | drain off bottom

Question 45

Example of anhydrous salt used for drying

Answer 45

MgSO4 | CaCl2

Question 46

How to dry with anhydrous salt

Answer 46

add and will absorb water | filter to remove hydrated salt

Question 47

How to purify an organic solid

Answer 47

- filter under pressure, buchner funnel attached to tap with filter paper dampened with solvent, wash product with solvent - recyrstallize by adding min amount of hot solvent until crystals dissolve, cool and recrystallize, filter under pressure, wash with cold solvent, dry, check melting point with melting point apparatus