Chapter 2 chemical engineering.pptxvihihigigicugu

Jcjkkkgjf

1. Chapter 2: facts about matter Section one: the three states of matter

2. Matter : is anything that occupies space and has mass. The three states of matter are solid, liquid, and gas. A physical change involves the conversion of a substance from one state of matter to another, without changing its chemical composition.

3. The three states of matter: Under normal conditions, there are three distinct states of matter: solids, liquids, and gases. Solids are relatively rigid and have fixed shapes and volumes (definite shapes and definite volume). A rock, for example, is a solid. In contrast, liquids have fixed volumes but flow to assume the shape of their containers, such as water in a bottle. Gases, such as air in an automobile tire, have neither fixed shapes nor fixed volumes and expand to completely fill their containers. Whereas the volume of gases strongly depends on their temperature and pressure the volumes of liquids and solids are virtually independent of temperature and pressure. Matter can often change from one physical state to another in a process called a physical change. For example, liquid water can be heated to form a gas called steam, or steam can be cooled to form liquid water. However, such changes of state do not affect the chemical composition of the substance. The term " phase " is sometimes used as a  synonym  for state of matter, but it is possible for a single compound to form different phases that are in the same state of matter. For example,  ice  is the solid state of water, but there are multiple  phases of ice  with different  crystal structures , which are formed at different pressures and temperatures.

4. Solids In solids, the forces keeping the particles together are relatively strong, and the particles stay very close to each other. The particles can vibrate but they are not moving around much. This is why solids are hard and rigid. Left on their own, solids will keep their shape.

5. Liquids In liquids, the forces between the particles are weaker than in solids. Particles are still fairly close together, but can move around freely. Liquids can flow around inside a container, and don’t have any particular fixed shape.

6. Gases Gases are difficult to relate to because they are often invisible, but found all around. You can feel them when, for example, the wind blows. You can sometimes smell them when, for example, you smell the odour of food that is cooking, or when a skunk has been upset. Some gases are important for our health (e.g., oxygen) while others can be deadly (e.g., hydrogen sulfide and chlorine). Before surgery, you may receive an anaesthetic gas غاز مخدر) ), which contains chemicals, to relieve pain and make you unconscious during the procedure. Gases are also responsible for the force of explosions. Gases have no definite volume and shape. The atoms and molecules move freely and spread apart from one another. They are compressible fluids. Not only will gases conform to the shape of their containers but they will also expand to fill the container.

7. Vocabularies hypothesis : A suggested explanation for a phenomenon to guide an experimental investigation. condensation:  To go from a gaseous state to a liquid state. evaporation: To change from a liquid state to a gaseous state. solidification:  The transition from a liquid state to a solid state. sublimation:  To change from a solid state directly to the gaseous state without going through a liquid phase. melting:  The change of state from a solid to a liquid. deposition:  The change of state directly from a gas to a solid. temperature:  The degree of hotness of a substance, related to the average kinetic energy of its molecules or atoms. pressure:  The pressure of a force upon a surface or an object by another force. boiling point:  The temperature required for a liquid to become a gas. melting point : The temperature required for a solid to become a liquid. freezing point: The temperature required for a liquid to change to a solid. plasma: A state, similar to a gas, where the electrons are not stuck with their atoms but are free in the cloud; plasma is naturally occurring in flames, lightning and auroras

8. Remember that a physical change: is a change in properties such as texture, shape, or state, while a chemical change represents the formation of a new substance after atoms are rearranged in a chemical reaction. The difference between a physical reaction and a chemical reaction is composition. In a chemical reaction, there is a change in the composition of the substances in question; in a physical change there is a difference in the appearance, smell, or simple display of a sample of matter without a change in composition. Although we call them physical "reactions," no reaction is actually occurring. In order for a reaction to take place, there must be a change in the elemental composition of the substance in question. Thus, we shall simply refer to physical "reactions" as physical changes from now on. Physical changes are limited to changes that result in a difference in display without changing the composition. Some common changes (but not limited to) are:

9. Texture→ الملمس Color → اللون Temperature → درجة الحرارة Shape→ الشكل Change of State→ التغير في الحالة Physical properties include many other aspects of a substance. The following are (but not limited to) physical properties. Density → الكثافة Viscosity → اللزوجة Solubility → الذوبان Mass→ الكتلة Volume→ الحجم

10. Section 2: the boiling point of water: The boiling point of water: is 100 °C or 212 °F at 1 atmosphere of pressure. Explanation: The boiling point of water depends on the atmospheric pressure, which changes according to elevation. Water boils at a lower temperature as you gain altitude (e.g., going higher on a mountain), and boils at a higher temperature if you increase atmospheric pressure (coming back down to sea level or going below it). If the external pressure is higher than one atmosphere, the liquid will boil at a higher temperature than the normal boiling point. If the force of attraction between the molecules is relatively strong, the boiling point will be relatively high

11. Section three: molecules in motion Molecular Motion Definition Molecular motion is defined as the movement of constituent particles or molecules in a certain direction. The molecular motions are affected by heat and temperature. This is because the temperature is the measurement of the average kinetic energy of the molecules and represents the motion of molecules.

12. Types of Molecular Motion: The different types of molecular motions are: Translational motion: In such kind of motion, molecules can move from one place to another in the same or different direction but always remains in the same axis. Rotational motion: In this type of motion, the molecule can rotate in and around the axis. Vibrational motion: In this type of motion, molecules can vibrate at their mean position. These motions are very common in  solid state . Electronic motion: In this type of motion, electrons can move from place to place. Electronic motions cause a change in the colour of substances.

13. Unlike the solid and liquid state, molecules in the gaseous state show random motion. That is the reason; gases take the shape of the container and spread quickly in space. The random motion of molecules in the gaseous state is due to high kinetic energy in molecules. They have weak intermolecular interactions between them. The intermolecular space between gaseous molecules is very large. They can show all the three types of molecular motion, vibrational , rotational and translational motion. In  vibrational motion, molecules move back and forth whereas in rotational motion the molecule rotates in space. In translational motion, molecules move in certain directions. Molecules of solid-state are capable of vibrational motion due to strong  intermolecular forces . The end of chapter