Well...this is Science.

martes, 30 de abril de 2013

How do liquids and gases change state?

Removing enough energy from a gas causes a gas to change into a liquid or a solid. Adding energgy to a liquid or a solid causes it to change into a gas. The process by which a liquid or a solid changes to a gas is vaporization.

By Evaporization or Boiling:

As a liquid is warmed, some particles gaine enough energy that they escape from the surface of the liquid and become a gas. This process is called evaporation.

A rapid change from a liquid to a gas, or vapor, is called boiling. This takes place throughout a liquid, not just at the surface. At a high temperature bubbles form. The specific temperature at which this occurs in a liquid is called the boiling point.

By Condensation:

As a gas is cooled its particles lose energy, and a liquid forms. The change of state from a gas to a liquid is called condensation.

Lesson 6: Changes of State

What happens when matter changes state?

The three most familiar states of matter are solid, liquid and gas.
A change of state is the change of a substance fromone physical form of matter to another. When a substance undergoes a physical change, it does not change its density, just its appearence.

Energy is Gained and Lost:

To change a substance to one state to another, energy must be added or removed. When a substance gains or loses energy, its temperature changes or its states changes. They do NOT happen at the same time.

Particle Motion Changes:

During a change of state, the motion of the particles in matter changes. Particles can break away from each other and gain more freedom to move. Particles can also attract each other more strongly, and have less freedomto move.

Energy is Conserved:

During a change of state, a substance must gain energy from the environment or ose energy to the environment, but the total amount of energy is conserved.

Solid Facts!

How do solids and liquids change states?

Removing energy from a liquid can cause it to change to a solid as the particles stop sliding past each other. Adding energy to a solid can cause it to change to a liquid as particles begin sliding past each other.

By Freezing:

The change of state in which a liquid becomes a solid is called freezing. When a liquid is cooled, it particles have less energy than they did before. Eventually, the particles lock into the fixed arrangement of a typical solid. The temperature at which a liquid substance change into a solid is the liquid´s freezing point.

By Melting:

When a solid is warmed, its particles have more energy than they did before. Eventually, the particles are are able to slide past one another. The change of state from a soid to a liquid is called melting. The temperature at which the substance changes from a solid to a liquid is called the melting point.

How do solids and gases change state?

Under the right conditions, some solids and gases canc hange state without ever becoming aliquid. The sustance must gain or lose a great deal of energy for this to occur.

By sublimation

The change from a solid state directly into a gas is called sublimation. As the particles of solid dry, ice gain energy their motion completely overcomes the atraction between the particles, and the oarticles escape into the air as gas.

By deposition

Deposition is the change in state from a gas directly to a solid. Deposition is the process by which ice crystals form in clouds. When conditions are rightm depostion occurs when the particles of a gas lose energy. Atracttion between particles locks the particles into the rigid structure of a solid. No liquid is formed in the process.

What happens to matter when a change of state occurs?

When matter changes from one state to another, it remains the same kind of matter. Its physical state changes, but its chemical identity does not.
The mass of a substance does not change when its state changes, Each state contains the same amount of matter.

Mixtures

What are mixtures?

A mixture is a combination of two or more substances that are combined physically but not chemically, they form a mixture if they do not change chemically to form a new substance. Unlike elements and compunds, mixtures are not pure substances, because they contain more than one type of substance. Each substance in a mixture has the same chemical makeup it had before the mixture formed.

Unlike pure substances , they do not have definite properties because they don't have a defined chemical makeup.

How can mixtures be classified?

Heterogeneous: mixture that does not have a uniform composition. In other tupes of mixtures, the sustances are evenly spread throughout.
Homegenous: susbtances that have a uniform composition.

As suspensions: suspensions are mixtures in which the particles of a material are spread throughout a liquid or gas but are too large to stay mixed without being stirred or shaken.

As solutions: In a solutions, one substance is dissolved in another substance.

As colloids: colloids are a third type of mixture that falls somewhere between suspensions and solutions. As in a suspension, the particles in a colloid are spreand throughout a liquid or a gas. Unlike the particles in a suspension, colloid particles are small and do not settle out quickly.

Lesson 4

Aloha! Ni Hao! Hola! Bonjour! Hello!

So this entry is gonna be about the lesson 4: pure substances and mixtures
Before starting with the actual topic, I shall explain some concepts to you, so let's begin.

Atom: are the smallest unit of an element that maintains the properties of that element. Is like a building block of matter.
Element: is made up of one or more of the same kind of atom chemically combined.
Compound: a compund is made up of different kinds of atoms chemically combined. Compounds have different properties from the elements that make them up.
Mixture: a mixture contains a variety of elements and compound that are not chemically combined with each other.

Elements and compounds are pure substances. Pure substance is asubstance that has definite physical and chemical properties such as appearence, melting point and reactivity.

Physical changes do not change the identity of the substance. The chemical bonds that hold atoms together cannot be broken easily. To break or form chemical bonds, a chemical change is required.

When a pure substance undergoes a chemical change, it is no longer the same substance. line-height: By knowing the category to which an element belongs, ypu can predict some of its properties

font-family: Times, 'Times New Roman', serif;">Element are broadly classified as metals, nonmetals or metalloids. There are over 100 elements known to exist and each one has a place in the periodic table of elements.

Compounds are grouped into basic categories by their properties.

By their pH: They can be classified as acidic, basic or neutral by measuring their pH. Acids have a pH below 7. Bases on the other hand have pH values greater than 7 and neutral compounds have a pH of 7.

Organic or Inorganic: In chemistry the word organic refers to compounds that contain carbon and hydrogen. Organic compounds are found in most foods. For example, gasoline contains a numer of organic ompounds, such as octane and heptane.

By their role in the body: Organic compounds that are made by living things are called biochemicals. They are divided into four categories: lipids, proteins, carbohydrates and nucleic acids. Carbohydrates are a source of energy. Lipids store excess energy. Proteins build and repair body structures and Nucleic acids contain genetic information (DNA).

What happen when substances change state?

...The motion of the particles change.
The particles of a substance, even a solid, are always in motion. As a solid is heated, its particles gain energy and if the vibrations are fast enough, the particles break loose. The process in which a solid becomes a liquid is known as melting.

As the temperature of a liquid is lowered, its particles lose energy. Eventually, the particles move slowly enough for the attractions between them to cause the liquid to become a solid. This process is called freezing.

Because water freezes at 0°C. Freezing does not happen only in low temperatures, some substances are frozen at room temperature or above. Example: An aluminum can.

When substances lose or gain energy, one of two things can happen:

Its teperature change.
Its state can change.

But both do NOT happen at the same time.
If you measure the temperature of boiling water, you will find that the temperature stays at 100°C until all of the liquid has become a gas.