Lecture 1 - Mass & Weight

Mass:

Mass is the amount of substance in matter. Mass tends to resist change in its state of rest or motion.

1. Smaller mass = Easier to move and easier to stop
• Example: A ball at rest can easily be set in to motion by a gentle push and a rolling ball can easily be stopped by using a hand.
2. Bigger mass = Harder to move and harder to stop
• Example: A parked truck cannot be set into motion unless and until a very large force is applied and a large force is needed to stop a moving truck.

Unit:

Mass is measured in g & kg. SI unit is kg.

Weight: 

Weight of a body is defined as the action of gravity on it. The greater the mass, the greater the weight and vice versa.

Weight = mass x acceleration due to gravity

w = mg

Unit:

Weight is measured in Newtons, symbol; N.

N = kgm/s²

w = mg where g is a constant; g = 10m/s²

so w is directly proportional to m.

Weight depends of acceleration due to gravity, if the gravitational field is changed, the weight changes.

Example: 1kg weighs 10N on earth where g = 10m/s² , but only 1.6N on moon where a = 1.6m/s²

Mass is independent of gravitational field and does not change with change in gravitational fields.

Mass measuring balances:

1. Precise/Accurate:
• A scientist in a lab or a gold seller uses precise balances to measure mass.
2. Non-Precise:
• Vegetable or meat vendors use a normal balance to measure mass, as precision here is important, yet not vital.

Example:

If a gold seller sells you an extra 1g of gold on a purchase; it will cause him a loss of $35, as gold is an expensive commodity costing $35/g; but if a bag of 1kg of apples costs $2, the fruit vendor can give you an extra 10g or so because that is affordable as apples only cost $0.002/g. Therefore, precision is always important but in some cases, it is more vital than others.

Lecture 9 – Sulphuric acid & the Contact Process

Sulphuric Acid:

Sulphuric acid is an extremely important industrial product. Many industries depend on using sulphuric acid.

Industrial manufacture of Sulphuric Acid:

Sulphuric Acid is industrially manufactured in a 7 step process, listed below:

1. Sulphur from the earth’s crust is burned in the presence of Oxygen to form Sulphur dioxide.
   
2. Sulphur dioxide is purified by passing through electrostatic dust precipitators to remove arsenic impurities. Arsenic impurities decrease the efficiency of Vanadium(V) oxide catalyst.
3. Sulphur dioxide and Oxygen are washed with water and dried before reaction.
4. Sulphur dioxide is reacted with more Oxygen to form Sulphur trioxide. This is a reversible reaction and therefore, the gaseous mixture is reacted at a temperature of 450°C and 2 to 3atm pressure, in a chamber of heated Vanadium(V) oxide mesh as a catalyst. This is the most critical step of the process and this manufacture of Sulphur trioxide is also known as the Contact’s Process.
   
5. The conditions for this process are strictly monitored and maintained to ensure a maximum yield of Sulphur trioxide.
6. Sulphur trioxide obtained by Contact’s process is dissolved in Sulphuric acid to form a dense liquid called, Oleum.
   
7. This oleum is diluted with distilled water to form Sulphuric acid.

Uses of Sulphur dioxide:

1. As a bleaching agent 
2. In the manufacture of wood pulp for paper
3. As an antibacterial for food preservatives

Uses of Sulphuric acid:

1. Detergents
2. Fertilizers
3. Battery acid

Lecture 8 – Nitrogenous fertilizers

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 7a	decorbestideas.tk
Figure 7b	www.royalqueenseeds.com

Uses of Ammonia:

The largest use of Ammonia is to manufacture nitrogenous fertilizers to improve agricultural growth. 

Nitrogenous fertilizers:

Nitrogenous fertilizers are necessary for plant growth and increasing the crop yield. They are rich source of nitrogen for the plants. Nitrogen in needed for plant growth as it is a constituent element of all proteins manufactured by the plant. Nitrogen also improves the immunity of the plants by defending it against pests and diseases. Nitrogen is also a constituent element of the green pigment in plants. This green pigment; chlorophyll; is essential for plants as it traps light energy during the manufacture of food by the plant during photosynthesis. Deficiency of nitrogen in plants can easily be identified by their dull yellowish appearance.

Figure 7a: Well – Nitrogened plant

Figure 7b: Nitrogen deficient plant

Bases when warmed with ammonium salt, react to form salt, water and release ammonia gas.  

This property of bases, becomes a menace in some agricultural areas where calcium hydroxide pellets are used to decrease the acidity of the soil. In such areas, calcium hydroxide with ammonium fertilizers in the presence of heat from the sun, reacts to form ammonia which escapes from the soil. Hence, this leads to a loss of nitrogen from the soil.