Chemical changes Flashcards
(27 cards)
What is a physical change?
A change which no new substances are formed
What is a chemical change?
A change which new subtances are formed
What are the types of chemical changes?
1.Reactions in which two or more substances chemically
combine to form one or more new substances
2.Reactions in which a substance breaks down into two or
more new substances
How can you tell there is a chemical change?
- Change in colour
- Change in temperature
- Production of gas
- Production of solid
What is the difference between a physical change and chemical change?
-In physical change, no new
substances are formed while in chemical change, one or more
new substances are formed
-In physical change, Changes can usually be reversed which are obtained back using separation techniques while in chemical change Changes are usually
not easily reversed can’t obtain
reactants back easily
What are word equations used for?
-Word equations show the substances that are involved in
chemical reactions - reactants used and products formed
-It also shows the condition under which a chemical
reaction occurs
What are the different types of chemical changes?
-Combustion
-Thermal decomposition
-Oxidation
-Neutralization
What is combustion?
-It is where a substance is heated in the prescene of oxygen to form one or more subtances
-Heat and light are usually given out
What is thermal decomoposition?
It is where a subtance breaks down into two or more simpler subtances when heating
What is oxidation?
-When a subtance gains oxygen, it undergoes a chemical change called oxidation
-Carbon dioxide and water are produced in this reaction
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 dissolves and dissociates
in water to produce hydrogen (H+) ions and the corresponding negative ions
What is a base?
A base is a substance that reacts with an acid to produce salt and water only. Bases are usually metal
oxides or hydroxides.
What is an alkali
An alkali is a base that dissolves and dissociates in water to produce hydroxide (OH-) ions and the corresponding positive metal ions. (mainly group I hydroxides)
What are the characteristics in acids?
-Sour taste
-Can burn the skin
-Turn blue litmus paper red
-React with alkalis, metals
and carbonates
-React with alkali in neutralisation reactions
What are the characteristics of alkali?
-Have a bitter taste
-Have a soapy feeling
-Can burn the skin
-Turn red litmus paper blue
-React with acids in neutralisation reactions
What safety precauctions must you take when handling corrosive subtances?
-Avoid direct or unprotected contact with these substances which can cause burns
-Wash any spilled acids/alkalis with lots of water
-Wear eye protection
-Use corrosion-resistant
containers and equipment
What equipment do you use to find the acidity or alkalinity of a solution?
-Use of ph scale
-Indicators
-ph meter
How does the use of a ph scale find the acidity or alkalinity of a solution?
Measures how acidic or alkaline a substance is which ranges from 0 to 14
How does the use of indicators find the acidity or alkalinity of a solution?
The indicators change colour accordingly in the prescene of an acid or alkali
What reaction does an acid+base form?
A neutralisation reaction which produces salt+water
What reaction does an reactive metal+acid form?
Acid can react with a reactive metal to form salt and hydrogen
gas
What reaction does an carbonate+water form?
An acid can react with a carbonate to form a salt, carbon
dioxide gas and water
What are the different types of salts that can be formed?
-hydrochloric acid
-nitric acid
-sulfuric acid
