Mrs Teo CCHwa Chong Institution

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heating iron and sulphur

1. A compound has 1. A compound has properties that are properties that are different from the different from the properties of its properties of its constituent elements.constituent elements.

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burning magnesium in air

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burning sodium in chlorine

2. When a compound is 2. When a compound is formed, energy (in the formed, energy (in the form of heat energy or form of heat energy or light energy or both) is light energy or both) is either taken in or given either taken in or given out to the surroundings.out to the surroundings.

3. A compound can only be broken down into simpler substances by chemical methods, such as decomposition by heat energy, exposure to light or passing an electric current through it.

4. The different elements 4. The different elements in a compound always in a compound always combine in a fixed combine in a fixed proportion by mass.proportion by mass.

4. The different elements 4. The different elements in a compound always in a compound always combine in a fixed combine in a fixed proportion by mass.proportion by mass.

For example, 1 g of For example, 1 g of hydrogen combines with hydrogen combines with only 8 g of oxygen to form 9 only 8 g of oxygen to form 9 g of waterg of water..

Some Examples of Some Examples of CompoundsCompoundsSome Examples of Some Examples of CompoundsCompounds

Sodium+

Chlorine

Hydrogen+

Oxygen

Carbon+

Hydrogen+

Oxygen

Calcium+

Carbon+

Oxygen

sodiumchloride

Water sugarLimestone (calciumcarbonate)

A compoundA compound is a substance is a substance consisting of two or more consisting of two or more elements chemically elements chemically combined.combined.

A compoundA compound is a substance is a substance consisting of two or more consisting of two or more elements chemically elements chemically combined.combined.

What is a What is a Compound?Compound?

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mixing iron and sulphur

1. A mixture has the properties of its components.

1. A mixture has the properties of its components.

Some Examples of Mixtures

• air

• soil

• blood

• sea water

2. When a mixture is produced, little or no energy is given out or taken in.

2. When a mixture is produced, little or no energy is given out or taken in.

3. A mixture can be separated into its components by physical means such as evaporation, filtration, distillation or using a magnet

3. A mixture can be separated into its components by physical means such as evaporation, filtration, distillation or using a magnet

4. The components in a mixture can be mixed in any proportion.

4. The components in a mixture can be mixed in any proportion.

What is a Mixture?

A mixture consists of two A mixture consists of two or more substances not or more substances not chemically combinedchemically combined..

What is a Mixture?

A mixture consists of two A mixture consists of two or more substances not or more substances not chemically combinedchemically combined..

Word EquationsWord Equations areare commonly commonly used for representing chemical used for representing chemical reactions.reactions.e.g.e.g.

1. 1. iron + sulphur

iron sulphide

2. magnesium + oxygen magnesium

oxide3. sodium + chlorine

sodium chloride

Word EquationsWord Equations areare commonly commonly used for representing chemical used for representing chemical reactions.reactions.

5. iron + hydrochloric acid

hydrogen + iron(II) chloride

4. oxygen + hydrogen

water

6. magnesium + hydrochloric acid

hydrogen + magnesium chloride

Video clip on reaction between 1. iron and sulphur2. calcium and water

The End