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GRADE 10

PHYSICAL SCIENCE

1.

Aluminium𝑨𝒍

phosphorus

carbon dioxide

Hydrogen sulfate

Hydrochloric acid

Sulfuric acid

𝑷

𝑪𝑶𝟐

𝑯𝟐𝑺𝑶𝟒

𝑯𝑪𝒍

𝑯𝟐𝑺𝑶𝟒

2.

Gaseous state (g)Liquid state (l)Solid state (s)Aqueous solution (aq)

𝑁2(𝑔) + 2𝑂2(𝑔) → 2𝑁𝑂2(𝑔)

3.

𝑁2(𝑔) + 2𝑂2(𝑔) → 2𝑁𝑂2(𝑔)

4.

𝑁2(𝑔) + 2𝑂2(𝑔) → 2𝑁𝑂2(𝑔)

2(𝑁𝐻4)2𝐶𝑂3

Examples• Write a balanced chemical equation for the following chemical reactions:

•Aluminium reacts with hydrogen chloride solution to form an aluminium chloride solution and hydrogen gas.

•Nitrogen gas reacts with hydrogen gas to form nitrogen hydride gas (ammonia gas)

Homework

EXERCISE 14 PG. 158-159

Energy changes

• Energy changes in chemical reactions are bigger than the energy changes in physical changes.

•During a chemical change, the temperature increases or decreases because the kinetic energy of the

particles change.

REMEMBERWhen bonds are broken – energy is absorbed

When new bonds are formed – energy is released

Calculating energy change

• Amount of potential energy absorbed to break the bonds –amount of energy released when bonds are broken

• If answer is + - endothermic reaction

(the product is colder than the reactants)

• If answer is - - exothermic reaction

(the product is hotter than the reactants)

• The following possible values are given for potential energies that are absorbed and released for a reaction.

• Calculate the energy change and determine whether the reaction is exothermic or endothermic.

Examples

Energy absorbed tobreak bonds(𝑘𝐽.𝑚𝑜𝑙−1)

Energy absorbed to

release bonds(𝑘𝐽.𝑚𝑜𝑙−1)

Energy change

(𝑘𝐽.𝑚𝑜𝑙−1)

Endothermic or exothermic

(𝑘𝐽.𝑚𝑜𝑙−1)

350 420

870 630

Examples•𝐶𝐶𝑙4 𝑔 + 2𝐹2 → 𝐶𝐹4 𝑔 + 2𝐶𝑙2 𝑔 + 752kJ

Exothermic or endothermic ?

Energy is released - hotter

Examples

•𝐶𝑙𝐹3 g + 514kJ → 𝐶𝑙 𝑔 + 3𝐹(𝑔)

Exothermic or endothermic ?

Energy is absorbed - colder

Homework

EXERCISE 15 pg. 160-161