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HIA International — Grade 8

Unit 1: Photosynthesis and the carbon cycle

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Unit 2: Properties of materials

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Unit 3: Forces and energy

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Unit 4: Maintaining life

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Unit 5: Reactivity

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Unit 6: Sound and space

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Unit 7: Genes and inheritance

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Unit 8: Rates of reaction

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Unit 9: Electricity

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Quiz

Checkpoint Grade 8 Unit 8 – 8.4 Detecting Chemical Reactions

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Detecting Chemical Reactions Checkpoint Chemistry quiz set 2: free practice for Cambridge Checkpoint (chemistry). Work through this Detecting Chemical Reactions Checkpoint Chemistry quiz set 2 and get instant feedback on every answer. If you get stuck, review the 16.4 Detecting chemical reactions lesson. More practice: Cambridge Checkpoint (chemistry) — all units. Syllabus: Cambridge Lower Secondary programme.

  • Questions count: 50
  • Passing grade: B+
  • Time limit:
Start Quiz
1.
Chloe put a flask of acid and marble chips (calcium carbonate) on a balance, with a cotton-wool plug in the neck, and recorded the mass. Which statement is supported by her graph?
Dr Dabour Hub Academy - figure 1
It stopped at about 4 minutes; 1.10 g of gas was lost
It stopped at about 6 minutes; 118.90 g of gas was lost
It stopped at about 2 minutes; 0.94 g of gas was lost
It never stopped, since the flask still had mass at 6 min
2.
Which step comes immediately after "observe for a precipitate or gas"?
mix reactants safely
record evidence of reaction
apply a gas test
3.
Which statement correctly describes precipitate?
a procedure using a characteristic observation to identify a gas
a gas giving a squeaky pop with a lighted splint
a gas that turns limewater cloudy
an insoluble solid formed from solutions
4.
Each option pairs a key term with an example. Which pairing is correct?
Reversible – bread being toasted
Irreversible – fruit going rotten
Irreversible – an ice lolly melting
Physical change – a nail rusting
5.
Salma mixed two clear solutions in front of a light sensor. Which conclusion do her readings best support?
A gas formed, and its bubbles let more light pass through
A solid formed, and the mixture was clear again by 150 s
Nothing formed, as light still passed through at 150 s
A solid formed, making it cloudy, and this stopped at about 90 s
6.
Hiro wants to compare the temperature changes of two different reactions. Which plan makes the comparison fair?
Use a larger volume for the reaction that looks slower
Start one mixture in a warm room and one in a cold room
Same volumes, same starting temperature, same insulated cup
Use a glass beaker for one and a foam cup for the other
7.
Which practical work belongs to Detecting Chemical Reactions?
Plan and evaluate a fair test comparing acids, alkalis or neutralisation reactions
Compare metal reactions and use the hydrogen “pop” test safely under supervision
Relate neutralisation to antacids, soil treatment and industrial waste treatment
Use observations, precipitates, temperature change and gas tests as evidence of reaction
8.
Which of these is the FIRST step in the correct order?
observe for a precipitate or gas
apply a gas test
record evidence of reaction
mix reactants safely
9.
Each option pairs a piece of equipment with its use when detecting reactions. Which pairing is correct?
Delivery tube – measures the temperature rise
Thermometer – collects the gas that is given off
Limewater – tests whether a gas is hydrogen
Gas syringe – measures the volume of gas made
10.
A white powder turns yellow when heated. On cooling it turns white again and its mass has not changed. What is the best conclusion?
It must be chemical, because the colour changed
It is probably a physical change, as it reverses
It must be chemical, because heat was supplied
It is a precipitate forming, as the colour changes
11.
Two solutions are mixed and the liquid turns cloudy. How could Priya best check that the cloudiness is a precipitate and not tiny gas bubbles?
Shake it hard to see whether it turns cloudier
Heat it strongly until all the liquid boils away
Leave it to stand, or filter it, to see if a solid collects
Add more of both solutions to see if it fizzes
12.
Amir wants to find out whether a vitamin tablet dissolving in water is a chemical reaction. Which plan would give the best evidence?
Time how long the tablet takes to disappear in the water
Record temperature, test any gas, and see if the solid is recovered
Watch whether the tablet gets smaller as it goes into the water
Weigh the tablet before adding it and then taste the solution
13.
Which student has drawn a valid conclusion from the observation?
Ana – a new solid formed from two solutions
Ben – his skin cooled, so heat was taken in
Chen – the water became cloudy with a solid
Dev – water appeared as the ice changed state
14.
Kwame mixed two colourless solutions and measured the temperature with a data logger and a glass thermometer together. Which conclusion is best?
A 0.4 °C rise happened that the thermometer could not show
No reaction took place, as the thermometer stayed at 20 °C
The data logger is faulty, as it disagrees with the thermometer
The temperature rose by 20.5 °C during the two minutes
15.
Mateo heated ice in tube A and white sugar in tube B, as shown. Both tubes formed droplets of water. Which conclusion is correct?
Dr Dabour Hub Academy - figure 2
Both are physical, because both of them made water
Only B is chemical: a black solid forms and stays
Both are chemical, because both of them were heated
Only A is chemical, because the solid ice disappeared
16.
For which change is there NOT yet enough evidence to say that a chemical reaction happened?
A – fizzing always needs a second sign to count
B – nothing happened apart from a solid appearing
C – its bubbles could simply be the liquid boiling
D – colour changes never show chemical reactions
17.
Lina used a temperature probe and data logger while she dropped magnesium ribbon into dilute acid. Which statement correctly describes her graph?
Dr Dabour Hub Academy - figure 3
Magnesium went in at 0 s; the temperature rose by 34 °C
Magnesium went in at 60 s; the temperature rose by 14 °C
Magnesium went in at 120 s; the rise was only 14 °C
Magnesium went in at 60 s; the rise was only 11.5 °C
18.
Nadia mixed citric acid solution with sodium hydrogencarbonate. It fizzed, and her thermometer readings are shown. She says: "It got colder, so this cannot be a chemical reaction." Which is the best reply?
Dr Dabour Hub Academy - figure 4
Wrong – a 6 °C fall is a temperature change, a sign of reaction
Right – chemical reactions only ever make mixtures hotter
Wrong – the thermometers show the temperature rose by 6 °C
Right – the fall of 32 °C shows the mixture is just cooling
19.
Why are most chemical reactions hard to reverse, while melting is easy to reverse?
Reactions make new substances; melting changes only the state
Reactions happen only at high temperatures; melting does not
Reactions destroy atoms, but melting leaves the atoms alone
Reactions always give off gas that is lost into the room
20.
Yusuf measured the temperature rise for different masses of magnesium powder in the same acid. Which conclusion do his results support?
The rise grows with mass, then stays at 12 °C once the acid runs out
The rise doubles every time the mass of magnesium is doubled
The rise grows with mass, then stops as the magnesium runs out
The temperature change is not linked to the mass of magnesium
21.
Which statement correctly describes hydrogen?
an insoluble solid formed from solutions
a procedure using a characteristic observation to identify a gas
a gas that turns limewater cloudy
a gas giving a squeaky pop with a lighted splint
22.
Each option pairs a sign of reaction with a way to detect it. Which pairing is correct?
Precipitate – test the mixture with a glowing splint
Gas given off – measure the mixture with a ruler
Temperature change – read a thermometer before and after
Colour change – listen closely for a squeaky pop
23.
Ravi collects the gas from magnesium and acid over water, as shown, filling three test tubes one after another. His teacher tells him not to use the first tube for the hydrogen test. What is the best reason?
Dr Dabour Hub Academy - figure 5
It holds steam from the water in the trough
It holds so much hydrogen it would explode
The gas in it is too cold for the splint to light
It holds mostly air pushed out of the flask
24.
Which statement correctly describes gas evolved?
not able to be changed back by simple physical means
a change such as dissolving or melting where no new substance forms
a gas given off, seen as bubbles or fizzing
a rise or fall showing energy has been transferred
25.
Blue copper sulfate crystals turn white when heated and water is given off. Adding water to the white powder makes it blue and hot. What does this show?
Heating the crystals was only melting them
No reaction happened, as blue came back
The water was a precipitate of the powder
Some chemical reactions can be reversed
26.
Each panel shows particles before and after a change. Blue and red circles are two different kinds of atom. Which panel shows a chemical reaction?
Dr Dabour Hub Academy - figure 6
P – the molecules have moved out of their neat rows
Q – the molecules have spread far apart from each other
R – the atoms have joined up into new molecules
S – two kinds of molecule are now mixed up together
27.
Each option pairs a change with a classification and reason. Which pairing is correct?
Chocolate melting – physical, it sets again on cooling
Bread toasting – physical, only the colour changes
Petrol burning – physical, the liquid just evaporates
Water freezing – chemical, a new solid substance forms
28.
Which statement correctly describes gas test?
an insoluble solid formed from solutions
a gas giving a squeaky pop with a lighted splint
a gas that turns limewater cloudy
a procedure using a characteristic observation to identify a gas
29.
Which statement correctly describes carbon dioxide?
an insoluble solid formed from solutions
a gas giving a squeaky pop with a lighted splint
a gas that turns limewater cloudy
a procedure using a characteristic observation to identify a gas
30.
Which control measure in the risk assessment is unsafe and should be changed?
The one for using the dilute hydrochloric acid
The one for the hydrogen "pop" test on the gas
The one for using a Bunsen burner in the lab
The one for heating a liquid in a test tube
31.
Ella will burn magnesium ribbon as shown, to see the signs of a reaction. She already wears goggles. Which further precaution is most important?
Dr Dabour Hub Academy - figure 7
Hold the ribbon in her fingers so that it cannot be dropped
Burn it inside a sealed jar so none of the gas can escape
Do not look straight at the flame, as the light harms eyes
Put water on the mat first so the white powder dissolves
32.
Which term is described as: an insoluble solid formed from solutions?
gas test
carbon dioxide
precipitate
hydrogen
33.
Which term is described as: a gas given off, seen as bubbles or fizzing?
gas evolved
temperature change
colour change
observation
34.
Which term is described as: a gas giving a squeaky pop with a lighted splint?
precipitate
gas test
carbon dioxide
hydrogen
35.
Which term is described as: a gas that turns limewater cloudy?
precipitate
gas test
hydrogen
carbon dioxide
36.
Which term is described as: a procedure using a characteristic observation to identify a gas?
precipitate
hydrogen
carbon dioxide
gas test
37.
To detect a temperature change during a reaction, you should use a _____ rather than touching the tube.
measuring cylinder
thermometer
lighted splint
balance (scale)
38.
A change in which no new substance is formed, and which can usually be reversed, is called a _____.
physical change
chemical reaction
irreversible change
precipitation
39.
A precipitate forming in a liquid is usually detected by seeing _____ appear in the mixture.
fizzing bubbles
a bright flame
cloudiness
steam rising up
40.
A chemical reaction always produces at least one _____.
type of gas
coloured liquid
solid precipitate
new substance
41.
The bubbles that appear when a bottle of fizzy water is opened are evidence of a chemical reaction. True or false?
True – bubbles always show a new gas
True – the water turns into a new gas
False – dissolved gas is just escaping
False – the bubbles are made of steam
42.
Statement: in an open beaker a gas-producing reaction shows a fall in mass, but a physical change such as melting does not change the mass. True or false?
False – melting makes the mass fall as well
False – mass is lost in every chemical reaction
True, but only if the beaker has been heated
True – only escaping gas lowers the reading
43.
A mixture becomes cloudy when a precipitate forms because tiny pieces of an insoluble solid are spread through the liquid. True or false?
True – the solid particles block light
False – the cloudiness is caused by gas
False – precipitates are always soluble
True, but only if the mixture is heated
44.
Iron filings mixed with sand can be pulled out with a magnet, which shows that mixing them was a physical change. True or false?
False – a new magnetic compound forms
False – iron and sand react when mixed
True, but only if the sand is also wet
True – the iron keeps its properties
45.
When zinc is added to dilute acid, bubbles on the zinc and a rising temperature are two separate signs of a chemical reaction. True or false?
False – only the bubbles count as evidence
True – a gas and a heat change both count
False – the rise is from the acid dissolving
True, but only if the zinc turns orange-brown
46.
Statement: the results show that only test 2 is a chemical reaction; the small pH change in test 1 is due to dilution by the water. True or false?
True – test 2 also fizzed and warmed up
False – any change in pH proves a reaction
False – dissolving the salt was a reaction
True, but only because the pH became 4
47.
Most physical changes, such as melting and dissolving, can be reversed quite easily. True or false?
False – they can never be reversed
True – no new substance forms
False – they make new substances
True, but only when done in water
48.
Steam condensing into droplets on a cold window is a physical change. True or false?
True – it is still water, just liquid
False – a new liquid is made on the glass
False – the droplets show a gas was formed
True, but only because the window is cold
49.
A physical change can alter the state, shape or size of a substance without making a new substance. True or false?
False – shape changes are chemical
False – a state change makes a new one
True – the substance stays the same
True, but only for metals and plastics
50.
A glow stick gives out light when bent but hardly warms up, so what happens inside it cannot be a chemical reaction. True or false?
True – every reaction has to give out heat
False – giving out light is a sign of reaction
True – light only comes from electric current
False – because it gets very hot when bent
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Part of Unit 8: Rates of reaction — see every lesson and quiz in this unit.
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