Chapter 11 Science Workbook Flashcards
What will happen if sodium hydroxide solution is added to dilute hydrochloric acid
A colourless solution is formed
What will happen if the mixture in the beaker is heated strongly?
The mixture will boil to dryness, leaving behind a white solid
Explain why antacids can be used to relieve the discomfort caused by excess acid in the stomach
Antacids contain alkaline compounds which can neutralise the excess acids in the stomach
A piece of magnesium was added to dilute hydrochloric acid observe what happened
Effervescence was formed and the magnesium ribbon becomes smaller and finally disappears
Light a wooden split and place it at the mouth of the test tube with hydrochloric acid and magnesium ribbon observe what happened
A ‘pop’ sound was heard
Calcium carbonate was put into a test tube of hydrochloric acid observe what happened
White precipitate was observed in limewater
What gas was given off when hydrochloric acid was added to magnesium
Hydrogen
What happened (observations) to sugar after it was heated for 2 min and what happened after 5 min
2 min: the sugar melted to form a colourless solution
5 min: the colourless liquid turned into a brown substance and a sweet smell was detected
What can chemical changes result from (4)and what does it usually involve (1)
Mixing of substances
Exposure to heat
Light
Electricity
Involves transfer of energy
How does neutralisation of acid on teeth by toothpaste benefit us
It prevents tooth decay
What is the benefit of release of energy from food?
Energy released from food via respiration allows us to carry out daily activities
Harmful effect of decay of apple
Food poisoning OR cause of wastage of food
Harmful effect of rusting of iron components
It causes metal structures to weaken
Harmful effect of combustion
Combustion of fuels releases carbon dioxide into the atmosphere and pollutes the environment and causes health problems
What does galvanising with zinc prevent?
Rusting of iron components
What does vacuum packaging prevent
Decay of an apple
Explain why the reaction (neutralisation) is a chemical change
The formation of new substances (potassium chloride and water) indicates that the reaction is a chemical change
Explain whether evaporation is a physical or chemical change
Physical change, the conversion of water to water vapour only involves a change in state and no new substances are formed.
Describe how the pH value changed when dilute sulfuric acid was added to the alkali in the beaker until the universal indicator turned green
The pH value in the beaker was above 7 when the universal indicator was first added to potassium hydroxide. The pH decreases as more dilute sulfuric acid was added until it reached pH 7 when potassium hydroxide was neutralise by sulfuric acid.
