Chemical reactions

What happens to milk when left at room temperature in summer?

It undergoes a chemical change, often resulting in spoilage.

What occurs when an iron tawa/pan is left exposed to a humid atmosphere?

It rusts, indicating a chemical change.

What is a chemical reaction?

A process in which the nature and identity of initial substances change.

What observations indicate that a chemical reaction has taken place?

Change in state, change in color, evolution of gas, change in temperature.

What is the word equation for burning magnesium in oxygen?

Magnesium + Oxygen → Magnesium oxide.

How can chemical equations be represented more concisely?

By using chemical formulae instead of words.

What signifies a balanced chemical equation?

The number of atoms of each element is the same on both sides of the equation.

Define combination reaction.

A reaction where two or more substances combine to form a single product.

What is an example of an exothermic reaction?

The burning of natural gas.

What is a displacement reaction?

A reaction where one element displaces another element from its compound.

What occurs in a double displacement reaction?

Ions are exchanged between two compounds.

What is oxidation in terms of a chemical reaction?

The gain of oxygen or the loss of hydrogen.

What is reduction in a chemical reaction?

The loss of oxygen or gain of hydrogen.

What is corrosion?

The deterioration of metals due to reactions with environmental substances.

What is rancidity?

The oxidation of fats and oils, resulting in off-tastes and smells.

What does the balanced equation 3Fe + 4H2O → Fe3O4 + 4H2 represent?

The balanced reaction involving iron and water producing iron oxide and hydrogen.

What chemical change occurs when calcium oxide reacts with water?

It forms slaked lime and releases heat.

How do you write a chemical equation with physical states?

Include symbols (s), (l), (g), (aq) to indicate solid, liquid, gas, and aqueous states.

What happens to silver chloride in sunlight?

It decomposes into silver and chlorine.

What type of reaction is indicated by the formation of a precipitate?

It is a double displacement or precipitation reaction.

What is a redox reaction?

A reaction involving oxidation and reduction where one substance loses oxygen and another gains it.

Give an example of a thermal decomposition reaction.

Calcium carbonate decomposing into calcium oxide and carbon dioxide upon heating.