Chemical Changes Flashcards
What are the 5 types of physical changes?
- Forming a mixture
- Change of state
- Change of size
- Heating/lighting effect of electricity
- Magnetic effect of electricity
State a difference between a physical and chemical change.
Physical change: No formation of new substances, properties of substance remains the same before and after change, none or little heat is taken in or given off.
Chemical change: Formation of new substances is present, properties of ending products are different from starting products, a lot of heat is taken in and given off.
What are the 5 causes of chemical change?
- Mixing
- Heat
- Oxygen
- Light
- Electricity
What are the two chemical changes by heat?
Combination and thermal decomposition.
What is combination?
2 or more substances combined to form a new substance with heat.
What is thermal decomposition?
Breaking down of a substance into 2 or more simpler substances by heat.
What are the 3 chemical changes by oxygen?
- Rusting
- Combustion/oxidation
- Cellular respiration
What is combustion/oxidation?
Combination of a substance with oxygen with the presence of heat.
What is cellular respiration?
Living cells or plants and animals taking in oxygen to release the energy stored in glucose.
What are the 2 chemical changes by light?
- Photosynthesis
- X-ray film
What are the 2 chemical changes by electricity?
- Electrolysis
- Electroplating
What is electrolysis?
Chemical decomposition of substances with the presence of an electric current.
What is electroplating?
Coating a substance with metal with a passage of an electric current.
What are some strong types of acids?
Hydrochloric acid, sulfuric acid and nitric acid.
What are some types of weak acids?
Malic acid, citric acid and ethanoic acid.
What are the properties of acids?
- Corrosive
- Turns blue litmus paper red, red litmus paper remains red.
- Reacts with metals, carbonates and alkalis.
- pH value <7
- Dissolve in water
- Conduct electricity
- Tastes sour
What are some types of strong alkalis?
Sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia hydroxide, magnesium hydroxide.
What is sodium hydroxide used for?
Make soaps and detergents.
What is potassium hydroxide used for?
Remove paints.
What are the properties of alkalis?
- Corrosive
- Turns red litmus paper blue, blue litmus paper remains blue
- Reacts with acids and ammonium salts
- pH value >7-14
- Dissolves in water
- conducts electricity
- Feels soapy and tastes bitter
State one similarity and difference between alkalis and acids.
Similarity: Both are corrosive/conduct electricity/dissolves in water.
Difference: Acids turn blue litmus paper red but alkalis turns red litmus paper blue/alkalis feels soapy and tastes bitter but acids tastes sour.
What is the chemical product of the reaction metal + acids?
Salt + hydrogen
What is the chemical product of the reaction carbonate + acid?
Salt + carbon dioxide + water
What is the chemical product of the reaction alkali + acid?
Salt + water
What happens when carbon dioxide is present in lime water?
White precipitate is formed, metal becomes smaller, effervescence of colourless, odourless gas evolved, increase in temperature and lighted splint extinguishes with a ‘pop’ sound.
What happens when hydrogen is present in lime water?
Metal becomes smaller, effervescence of colourless, odourless gas evolved, increase in temperature and lighted splint extinguishes.
How does an indicator work?
An indicator is a substance which changes colour depending on whether the solution being tested is acidic or alkaline.
What is the pH value and colour of detergent?
Violet, pH 14.
What is the pH value and colour of distilled water?
Green, pH 7.
What are the 5 beneficial uses of effects of chemical change?
- Decomposition
- Fuel combustion
- Cooking
- Production of materials, medicine and fertilisers
- Natural processes such as reproduction, digestion, growth and photosynthesis
What are the 5 harmful effects of chemical change?
- Air pollution
- Acid rain
- Rusting
- Decomposition
What is the harmful and useful effect of fuel combustion?
Harmful: Releases air pollutants into the atmosphere - gases such as sulfur dioxide dissolves in rain, which corrodes buildings and other structures. Polluted air results in difficulty breathing and risk of respiratory illnesses.
Useful: Releases energy to more vehicles.
What does acid rain do?
It is resulted from fuel combustion destroys plants and kills fishes and other aquatic life.
What is rusting?
When iron rusts, structures such as bridges become corroded can be unsafe. Rusting causes loss of finite natural resources.
What is the harmful and useful effect of decomposition?
Harmful: Waste of food supply and resources.
Useful: Breaks down unwanted matter and releases nutrients back to earth to prevent too many dead organisms from piling up on earth.
