RnR chem01 (0654s22)

Which piece of apparatus is used to measure the change in the volume of a liquid most accurately?

• A

• B

• C

• D

Answer explanation

Question asked for accuracy therefore the

burette is more accurate to 0.05cm³

if pipette (D) though accurate BUT it can only measure exact amount of volume

measuring cylinder's accuracy is up to 0.5cm³ whereas the conical flask has an accuracy of either 10cm³ or 25cm³ depending on size of conical flask

Some physical and chemical changes are listed.

1 burning methane

2 dissolving sugar in water

3 evaporating ethanol

4 rusting iron

Which changes are chemical changes?

• 1 and 2

• 1 and 4

• 2 and 3

• 3 and 4

Answer explanation

Physical change: reactants and products are the same

Chemical change: produce NEW product or products

burning methane (CH₄) becomes CO₂ & H₂O

dissolving sugar in water: still sugar and water

evaporating ethanol: liquid ethanol becomes gaseous ethanol !!

rusting iron: Iron (Fe) becomes Iron oxide (Fe₂O₃)

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which equation is balanced?

• A

• B

• C

• D

Answer explanation

Make sure that the number of molecules on the left side and right side are balanced (equal)

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which word describes reactions that give out heat energy?

• endothermic

• exothermic

• oxidation

• reduction

Answer explanation

Question mentioned "gives out" which means heat energy exit (released)

Tags

NGSS.HS-PS1-4

When solid pieces of calcium carbonate are added to dilute hydrochloric acid in a flask,

carbon dioxide gas is given off. The mass of the flask and its contents are measured over time. Two different experiments are carried out. In both experiments the acid is in excess.

The results of these two experiments are shown.

Which statement explains the different shapes of the curves?

• Experiment 2 uses a catalyst.

• Experiment 2 uses acid at a higher temperature.

• Experiment 2 uses acid that is more dilute.

• Experiment 2 uses powdered calcium carbonate.

Answer explanation

when looking at both curves, the gradient for expt. 2 shows that the mass of the calcium carbonate reacting is less per unit time meaning that slower reaction (gradient less steep) compared to expt. 1

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

When aqueous potassium hydroxide is warmed with ammonium chloride, a gas is given off.

Which test result identifies the gas?

• It bleaches pH paper.

• It turns anhydrous cobalt(II) chloride blue.

• It turns universal indicator red.

• It turns red litmus blue

Answer explanation

"...potassium hydroxide (an alkali) is warmed with ammonium chloride"

from this we can deduce that Ammonia gas will be produced which is an alkaline gas.

test for alkali is using red litmus paper which turns blue OR universal indicator (which will also turns blue in the presence of alkali)

Tags

NGSS.MS-PS1-2

Which row does not link a general physical property to the type of element?

• A

• B

• C

• D

Answer explanation

Recall the properties between metals and non-metals...

metals are malleable (can be bent... metals we are talking about NOT alloys)

metals are good conductors of BOTH electricity and heat

ALL non-metals are poor conductors of heat and electricity as they do not have free moving electrons!!

but there are non-metals which do not have low melting point

Which colour change is observed when water is tested using copper(II) sulfate?

• blue to pink

• blue to white

• white to blue

• white to pink

Tags

NGSS.MS-PS1-2

What are the products of the complete combustion of ethanol?

• carbon dioxide and hydrogen

• carbon dioxide and water

• carbon monoxide and hydrogen

• carbon monoxide and water

Answer explanation

since when is hydrogen given out during combustion??

and if COMPLETE combustion it is always CO₂ and H₂O

if INCOMPLETE??? i hope you can recall the products