chemical changes Flashcards
Memorisation (49 cards)
What are reactants?
Substances that react with each other are known as
reactants
What are products?
The new substances formed are called products
1st type of reaction
Reactions in which two or more substances chemically
combine to form one or more new substances
Eg: carbon burns in oxygen to form carbon dioxide and
water
2nd type of reaction
Reactions in which a substance breaks down into two or
more new substances
Eg: when calcium carbonate is heated, it breaks down
into carbon dioxide and calcium oxide
How can you tell there is a chemical change?
- Change in colour
- Change in temperature
- Production of gas
- Production of solid
What is combustion?
Substance is heated in the presence of oxygen
● To form one or more substances
Heat and light are usually given out
methane + oxygen → carbon dioxide + water
What is thermal decomposition?
Substance breaks down into two or more
simpler substances upon heating
What is oxidation?
Matter is able to interact with oxygen
● When a substance gains oxygen, it undergoes a
chemical change called oxidation
Example: Rusting of nails
● Iron reacts with oxygen and water to form rust,
which is a reddish brown flaky substance
Iron + oxygen → iron(III) oxide
Example: cellular respiration
● Food molecules such as glucose are broken down in
the presence of oxygen to provide cells with energy
● Carbon dioxide and water are produced in this
reaction
What is neutralization
When an acid is mixed with an alkali, a
neutralisation reaction occurs
What is a 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)
Acidity or alkalinity of a
solution
Bases alkalis “All alkalis are bases,
but not all bases are alkalis”
Acids
Sour taste
● Can burn the skin
● Turn blue litmus paper red
● React with alkalis, metals
and carbonates
Alkalis
Have a bitter taste
● Have a soapy feeling
● Can burn the skin
● Turn red litmus paper blue
● React with acids in neutralization reactions
Reactions of Acids
with Alkalis
- Acid + alkali
● Neutralisation reaction
● Products: salt and water
● Word equation:
Acid + alkali → salt + water
Hydrochloric acid + sodium hydroxide → sodium chloride + water
The type of salt formed from an acid reaction
depends on the type of acid that is used
● Salts formed from hydrochloric acid are
chlorides
● salts formed from nitric acid are nitrates
● salts formed from sulfuric acid are sulfates
Fill in the blanks.
1. Hydrochloric acid + sodium hydroxide → ??? + water
2. Nitric acid + potassium hydroxide → ??? + water
3. Sulfuric acid + sodium hydroxide → ??? + water
Example:
1. hydrochloric acid + sodium hydroxide → sodium chloride + water
2. nitric acid + potassium hydroxide → potassium nitrate + water
3. sulfuric acid + sodium hydroxide → sodium sulfate + water
Reactions of Acids
with Metals
● Acid can react with a reactive metal to form salt and hydrogen
gas
● Word equation:
Acid + metal → salt + hydrogen gas
Hydrochloric acid + magnesium → magnesium chloride + hydrogen
● Hydrogen gas can be tested by using a lighted splint
● It will extinguish with a pop sound in the presence of hydrogen
gas
Fill in the blanks.
1. Nitric acid + magnesium → ??? + hydrogen gas
2. Hydrochloric acid + calcium → ??? + hydrogen gas
3. ??? + ??? → potassium sulfate + hydrogen gas
Fill in the blanks.
1. Nitric acid + magnesium → magnesium nitrate + hydrogen gas
2. Hydrochloric acid + calcium → calcium chloride + hydrogen gas
3. sulfuric acid + potassium → potassium sulfate + hydrogen gas
Reactions of Acids with
Carbonates
An acid can react with a carbonate to form a salt, carbon
dioxide gas and water
● Word equation:
● Acid + carbonate → salt + carbon dioxide + water
Example:
Nitric acid + calcium carbonate → calcium nitrate + carbon dioxide + water
Fill in the blanks.
1. Nitric acid + potassium carbonate → potassium nitrate + ?? +
water
2. ??? acid + ??? carbonate → copper sulfate + carbon dioxide +
water
3. Hydrochloric acid + lithium carbonate → ??? + carbon dioxide +
water
Fill in the blanks.
1. Nitric acid + potassium carbonate → potassium nitrate + carbon
dioxide + water
2. sulfuric acid + copper carbonate → copper sulfate + carbon
dioxide + water
3. Hydrochloric acid + lithium carbonate → lithium chloride + carbon
dioxide + water
Magnesium
Mg
Sodium
Na
Zinc
Zn
Aluminum
Al
