Observations and Measurements
164 questions· page 1 of 17
Baking soda is used to make bread rise. When baking soda is heated, it decomposes and carbon dioxide gas is released.
Baking soda also decomposes gradually when it is stored. The longer the baking soda is stored, the less carbon dioxide it releases when it is heated.
Plan an investigation to show which of two different samples of baking soda has been stored for longer.
Your plan should include the use of common laboratory apparatus and the two samples of baking soda. No other chemicals should be used.
Your plan should include:
- the apparatus needed
- the method to use
- the measurements to take
- the variables to control
- how to use the results to determine which sample has been stored for longer.
You may draw a diagram to help you answer the question.
A student is provided with two bottles labelled A and B and a supply of water.
One of the bottles contains of solid potassium chloride, .
The other bottle contains of solid calcium chloride, .
When potassium chloride dissolves in water the change is endothermic.
When calcium chloride dissolves in water the change is exothermic.
Plan experiments, based on dissolving the solids in water, to decide:
- which compound is in each bottle
- which compound produces the greatest heat change per gram of solid.
Your plan may use any of the apparatus normally found in a chemistry laboratory but no other chemicals.
Your plan must state all the measurements you need to make.
Your plan must use the same experimental procedure for each solid.
Bromine, chlorine, fluorine and iodine are elements in Group VII of the Periodic Table.
Group VII elements react with compounds of Group VII elements in aqueous solution in displacement reactions. More reactive elements displace less reactive elements from their compounds. For example:
You have access to:
- colourless aqueous solutions of potassium bromide, potassium chloride and potassium iodide
- aqueous solutions of bromine (orange), chlorine (yellow) and iodine (brown)
- the apparatus normally found in a school laboratory.
No other chemicals are available.
Plan experiments using these solutions to show that:
- chlorine is more reactive than bromine and iodine
- bromine is more reactive than iodine but less reactive than chlorine.
Your plan must include:
- what you need to do
- the observations you expect
- an explanation of how these observations show the order of reactivity of bromine, chlorine and iodine.
Carbon and copper(II) oxide are both black solids. Copper(II) oxide reacts with dilute sulfuric acid to form an aqueous solution. Carbon does not react with or dissolve in dilute sulfuric acid. Neither carbon nor copper(II) oxide dissolve in water.
A mixture contains carbon and copper(II) oxide only.
Plan an experiment to produce a sample of pure carbon from the mixture.
You may use:
- dilute sulfuric acid
- distilled water
- any of the apparatus usually found in a chemistry laboratory.
No other chemicals are available.
Your plan should include details of:
- how to dissolve the copper(II) oxide in the dilute sulfuric acid
- how to separate the carbon
- how to purify the carbon
- observations occurring at each stage of the process.
Chemical equations are not required.
A student is provided with three solutions:
- aqueous zinc sulfate
- aqueous copper(II) sulfate
- aqueous calcium nitrate.
The student tests the three aqueous solutions by adding each reagent shown in the table.
Record the observations in the table.
Write ‘no reaction’ where appropriate.
| solutions | reagents: aqueous sodium hydroxide | reagents: aqueous sodium hydroxide in excess | reagents: aqueous barium nitrate and dilute nitric acid | reagents: aluminium and aqueous sodium hydroxide + heat |
|---|---|---|---|---|
| aqueous zinc sulfate | ||||
| aqueous copper(II) sulfate | ||||
| aqueous calcium nitrate | name of gas = ______ test for gas = ______ result of test = ______ |
M is a compound which contains three ions.
Complete the table by adding the conclusion for (a), the observations for (b)(i), (ii) and (iii), and both the test and observation for (c).
| test | observations | conclusions | |
|---|---|---|---|
| (a) | M is dissolved in water and the resulting solution divided into two parts for use in tests (b), (c). | A coloured solution is formed. | |
| (b) | (i) To the first part, aqueous sodium hydroxide is added until a change is seen. (ii) An excess of aqueous sodium hydroxide is added to the mixture from (i). (iii) This mixture is heated. | M contains ions. M contains ions. M contains ions. | |
| (c) | M contains ions. |
What is the volume of liquid in the measuring cylinder?
______
The following table shows the tests a student did on compound W.
Complete the table by adding the observations for (a), (c)(i) and (c)(ii) and the tests and observations for tests (b)(i), (b)(ii) and (d).
| test | observations | conclusions |
|---|---|---|
| (a) W was dissolved in water and the resulting solution divided into three parts for tests (b), (c) and (d). | Transition metal ions are not present in the solution of W. | |
| (b) (i) (ii) | W may contain ions or ions. | |
| (c) (i) To the second part aqueous ammonia was added until a change was seen. (ii) An excess of aqueous ammonia was added to the mixture from (i). | The presence of ions was confirmed. | |
| (d) | W contains ions. |
The student heats the copper in air to form copper(II) oxide.
Give the formula and colour of copper(II) oxide.
formula ______
colour ______
Name the coloured compound present in the aqueous solution formed and give its colour.
name ______
colour ______
Half of the solution from (b) is poured into a beaker. Some powdered zinc is added to this solution and left for a while.
Describe what is seen.
Complete the table.
| anode (+) | anode (+) | cathode (–) | cathode (–) | |
|---|---|---|---|---|
| solution | name of product | observation | name of product | observation |
| aqueous copper(II) sulfate | oxygen | |||
| concentrated aqueous sodium chloride | chlorine | hydrogen |