Chemical changes Flashcards
Define a physical change.
A physical change is a change in which no new substances are formed. e.g. boiling, dissolving and melting
Define a chemical change.
A chemical change is a change in which one or more new substances are formed.
e.g. burning fuel to form carbon dioxide and water
What is combustion?
Combustion is a a chemical reaction in which a substance is heated in the presence of oxygen to form one or more new substances.
What is thermal decomposition?
Thermal decomposition is a process in which a substance breaks down into two or more simpler substances upon heating.
What is oxidation?
When a substance gains oxygen, it undergoes a chemical change called oxidation.
What is neutralisation?
When an acid is mixed with an alkali, a neutralisation reaction occurs.
What is an acid?
An acid is a substance that produces hydrogen ions, H +, in aqueous solution.
What are the properties of acids?
Acids have a sour taste. Acids turn blue litmus paper red. Acids dissolve in water to form solutions that conduct electricity.
What is an alkali?
An alkali is a substance that produces hydroxide ions, OH-, in aqueous solution.
What are the properties of alkalis?
Alkalis feel soapy and have a bitter taste too. Alkalis turn red litmus paper blue. Alkalis reacts to acids to from water and salt only.
What is a test for hydrogen gas?
Place a lighted splint near the mouth of the test tube containing hydrogen gas. Hydrogen gas extinguishes the flame with a ‘pop’ sound.
What is a test for carbon dioxide? What is the observation?
Bubble the gas through limewater.
Observation: Carbon dioxide forms a white precipitate with limewater.
What is formed when an acid is mixed with an alkali?
Salt and water.
acid+ reactive metal=?+?
salt+ hydrogen gas
acid+ carbonate=?+?+?
salt+ water+ carbon dioxide
