S2 Chemistry Flashcards
Revision
What are the signs of a chemical reaction?
A colour change
A temperature change
A gas being released - look for fizzing or bubbles
A solid being formed
What can you do to increase the speed of a reaction?
Decrease the particle size
Increase temperature
Increase concentration
Adding a catalyst
What is a catalyst?
A catalyst is a substance which speeds up a chemical reaction & is not used up in the reaction.
What is the name of a biological catalyst?
The catalyst present in living things are enzymes, sometimes also called biological catalysts.
Magnesium + _ _ _ _ _ _ = Magnesium Oxide
Oxygen
Carbon + _ _ _ _ _ _ = Carbon dioxide
Oxygen
Oxygen + _ _ _ _ _ _ = water
Hydrogen
If a substance has a pH of 3 is this an acid or an alkali?
A substance with a pH of 3 is an acid.
If a substance has a pH of 14 is this an acid or an alkali
A substance with a pH of 14 is an alkali.
A substance with a pH of 7: Is this an acid or an alkali?
A substance with a pH of 7 is neutral.
A substance with a pH of 7.4: Is this an acid or an alkali?
A substance with a pH of 7.4 is an alkali.
Which pH range do gastric juice have?
a) Around pH 2
b) Around pH 7
c) Around pH 9
a) Gastric juices have a pH around 2.
Which pH range do hand soap or cleaning fluids that contain bleach have?
a) Around pH 2-3
b) Around pH 7
c) Around pH 10-12
c) Hand soap or cleaning fluids that contain bleach have a pH of around pH 10-12.
What colour does red cabbage indicator turn when you add acids?
Red cabbage indicator turns pink when you add acids.
What colour does red cabbage indicator turn when you add alkalis?
Red cabbage indicator turns green when you add alkalis.
What colour does red cabbage indicator turn when you add a neutral substance?
Red cabbage indicator stays purple when you add a neutral substance.
Write the word equation that shows what happens when an acid and an alkali react.
An acid an an alkali neutralise and form salt and water:
acid + alkali –> salt + water
What type of salt is produced by hydrochloric acid?
Hydrochloric acids produce chlorides.
What type of salt is produced by sulfuric acid?
Sufuric acid produces sulfates.
What type of salt is produced by nitric acid?
Nitric acid produces nitrates.
Write the word equation when sodium hydroxide (an alkali) reacts with hydrochloric acid.
Sodium hydroxide + hydrochloric acid
–>
Sodium chloride + water
Write a chemical reaction for this example:
Hydrogen reacting with oxygen to produce water.
Hydrogen + Oxygen –> Water
Write a chemical reaction for this example:
Sodium chloride is produced by reaxcting sodium and chlorine.
Sodium + Chlorine –> Sodium chloride
Chemical reaction? Yes or No?
A solid forming when two solutions are added together.
Yes, this is a chemical reaction.
Chemical reaction? Yes or No?
Separating chalk from water.
No, this is a physical separation, not a chemical reaction.
Chemical reaction? Yes or No?
A puddle evaporating.
No, this is a physical change of state, not a chemical reaction.
Chemical reaction? Yes or No?
Making magnesium and oxygen from magnesium oxide.
Yes, this is a chemical reaction.
Chemical reaction? Yes or No?
Adding calcium to water - it fizzes and gets hot.
Yes, this is a chemical reaction.
In which experiment would the aspirin take the longest to dissolve?
a) aspirin tablet, water at 20 degrees C
b) aspirin powder, water at 40 degrees C
c) aspirin powder, water at 30 degrees C
d) aspirin tablet, water at 40 degrees C.
a)
Explanation: Using a tablet instead of powder decreases the rate of reaction; the lower temperature also decreases the rate of reaction
Which two experiments should be compared to show the effect of particle size on the speed of dissolving?
a) aspirin tablet, water at 20 degrees C
b) aspirin powder, water at 40 degrees C
c) aspirin powder, water at 30 degrees C
d) aspirin tablet, water at 40 degrees C.
b & d
Explanation: The temperature needs to stay the same (40 degrees) as it is a controlled variable; the only thing changing (the independent variable) is aspirin powder vs aspirin tablet.
Nitric acid reacts with an alkali to form sodium nitrate and water. What is the alkali?
Sodium hydroxide
Lithium chloride is made when lithium hydroxide reacts with which acid?
Hydrochloric acid
Why can experiments c and d not be used to investigate the effect of particle size on dissolving?
a) aspirin tablet, water at 20 degrees C
b) aspirin powder, water at 40 degrees C
c) aspirin powder, water at 30 degrees C
d) aspirin tablet, water at 40 degrees C.
The temperature is also changing, so the results would be invalid. Only one thing (the particle size, i.e. powder vs tablet) should change to get valid results.
Sulfuric acid and sodium hydroxide react. What is the salt called that is made in this reaction?
Sodium sulfate
Copper carbonate solution (green) is easily decomposed by heating. As a result, the solid copper oxide (black) is formed and the gas carbon dioxide is also released. What signs of a chemical reaction are shown in this example?
There is a colour change (green to black), a solid is formed and a gas is released.
