Review of Chemistry topics learned in Primary Science

Topics covered in primary science, which are studied under Chemistry include: Properties of matter, mixtures and methods of separation, drugs and pollution.

Matter

Matter is anything that has mass and occupies space. Matter exists in three states namely solid, liquid and gas (vapour).

The three states of matter are inter - convertible.

Properties of matter

Physical properties of solids

Solids have definite shapes that are not easily changed. Solids also have a definite mass and volume.

Mass is a measure of the amount of matter in a substance. Volume is the space occupied by a substance.

Different sizes of the same substance contain different amounts of matter and therefore have different masses. When a solid is put in water, the water level rises. The rise in water level represents the volume of the solid.

Physical properties of liquids

Liquids have a definite mass and volume but take the shape of the containers in which they are placed due to their ability to flow.

Physical properties of gases.

Gases have a definite mass but do not have definite volume or shape. They can therefore be compressed to occupy small spaces and also expanded.

Mixtures

Matter is found either as pure substances or mixtures. A pure substance is one that consists of only one type of matter.

A mixture consists of two or more substances mixed together and in which the individual components forming the mixture retain their physical and chemical properties.

A mixture can be separated by physical means such as winnowing, sieving, filtering, evaporating, decanting and use of magnets. The choice of method to separate a given mixture depends on the nature and properties of the individual components forming the mixture.

Conductors and non-conductors

Substances which allow electrical energy to flow through them are conductors.

Substances which do not allow electricity to flow through them are non-conductors.

Drugs and drug abuse

A drug is any substance, natural or manufactured which when used alters the way the body functions.

Drugs used to treat diseases in human beings and other animals are known as medicines.

Medicines are administered by qualified medical officers in specific amounts called doses.

The written instructions by a qualified medical officer, giving details on the type of drugs and how the drugs should be used is called a prescription.

The use of a drug for a purpose other than what it is meant for, or use of overdose or underdose of prescribed drugs constitutes drug abuse.

Drug abuse has harmful effects on the state of health of the user. The harmful effects include stress, depression, hallucination, addiction and dependency or may be fatal.

The commonly abused drugs are tobacco, alcohol, bhang and khat (miraa).

Harmful effects of smoking tobacco include lung cancer and heart failure.

Alcohol abuse leads to liver problems (liver cirrhosis).

Misuse of bhang leads to mental disorders.

Prolonged use of khat leads to addiction, dependency and vascular disorders.