Chemistry Form 4 Chapter 2 Essay

 

Matter

-

Is anything that occupies space and has mass.

-

Is made up of tiny and discrete particles.

-

There are spaces between these particles.

-

These particles may be atoms, molecules or ions.

-

Matter exists in three states

solid, liquid and gas2

Element

-

Is a substance that consists of only one type of atom3

Compound

-

Is a substance that contains two or more elements that are chemically bonded together

-

Molecule, Ion4.

Atom

-

An atom is the smallest particle of an element that can participate in a chemical reaction.

-

Metals and some non metals such as carbon and helium exist as atoms.

-

Fe, Al, Mg, Au5.

Molecule

-

Is a group of two or more atoms which are chemically bonded together

-

O

2

, H

2

, H

2

O, CO

2

6.

Ion

-

Is a positively-charged or negatively-charged particle.

-

Sodium Chloride, NaCl: Na

+

, Cl

-

7.

Diffusion

-

Occur when particles of a substance, move in between the particles of another substance.

-

Occur most rapidly in gases, slower in liquids and slowest in solids.8.

The Kinetic Theory of Matteri. Solid

-

a solid has a fixed volume and shape

-

a solid cannot be compressed

-

the particles are packed closely together in an orderly manner

-

there are strong forces between the particles

-

the particles can only vibrate and rotate about their fixed positions

ii. Liquid

-

a liquid has fixed volume. It does not have a fixed shape but takes the shape of the container

-

a liquid cannot be compressed easily

-

The particles are packed closely together but not in orderly arrangement

-

The particles are held together by strong forces but weaker that the forces in a solid

-

The particles can vibrate, rotate and move through the liquid. They collide against each other

iii. Gas

-

a gas does not gave a fixed shape or volume

-

a gas can be compressed easily

-

the particles are very far apart from each other and in a random motion

-

there are weak forces between the particles

the particles can vibrate, rotate and move freely. The rate ofcollision is greater that the rate of collision in a liquid

2 Study Smart www.studysmart.page.tl C) IONS  An atom or a group of atoms that has acquired a net electric charge by gaining or losing one or more electrons.  Ions that are positively charged is called cations (loss of electron)  Ions that are positively charged is called anions (gain/accept electron)  Examples: Oxygen ion Hydrogen Ion Hydroxide ion 2- + - CRITICAL THINKING : What do we call ions that consist of more than 1 elements, such as OH-, SO 4 2-? ELEMENTS AND COMPOUND  Matter can either exist as an element or a compound.  Element is a substance that cannot be broken down into simpler substances by chemical nor physical methods.  An element consists of only one type of atom. Element can be either atoms or molecules.  Examples: Magnesium;Mg , Sodium;Na , Sulphur;S , Hydrogen;H  Compound is substance containing 2 or more elements chemically joined together  A compound is made up of either molecules or ions.  Examples, Magnesium is an element; oxygen is an element – they can only be burnt to form magnesium oxide compound. Magnesium,Mg Element Oxygen,O Element Magnesium oxide, MgO Compound CRITICAL THINKING : What is the difference between Molecules and Compound ? Diffusion  Particle of a substance move in between particles of another substance  Example : Bromine Gas A gas jar is filled with bromine gas and covered with another inverted gas jar. After few minutes, the color of gas jar is observed CRITICAL THINKING: What will be the diffusion rate in liquid & solid substances? (Slower than gas or faster than gas ? Why? O H O H Mg O Mg O

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