In science there is a lot of changes in matter, There are two types, Physical
and Chemical…
Matter is anything that has mass and volume.
To understand changes in matter, you need to know what the sample of matter was like before the change and what it is like after the change. You also need to be able to describe and classify matter.
States of Matter:
Solid
Liquid
Gas
Any kind of matter can be classified as a
mixture or a pure substance.
Mixture--matter that has two or more kinds of particles and thus may have different properties in different samples
Pure substance--a substance that has the same properties in any sample you choose. There are two kinds of pure substances: elements and compounds.
A physical change in a substance doesn't change what the
substance is. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.
For example, if a piece of paper is cut up into small pieces it still is paper. This would be a physical change in the shape and size of the paper. If the same piece of paper is burned, it is broken up into different substances that are not paper.
Physical changes can be reversed, chemical changes cannot be reversed with the substance changed back without extraordinary means, if at all. For example, a cup of water can be frozen when cooled and then can be returned to a liquid form when heated.
If one decided to mix sugar into water to make sugar water, this would be a physical change as the water could be left out to evaporate and the sugar crystals would remain. However, if one made a recipe for a cake with flour, water, sugar and other ingredients and baked them together, it would take extraordinary means to separate the various ingredients out to their original form.
When heat is given off in a chemical change or reaction, it is called an exothermic reaction. When heat is absorbed in a chemical change or reaction, it is called an endothermic reaction. The speed at which chemical reactions take place depend on the temperature pressure and how concentrated the substances involved in the chemical reaction are. Sometimes substances called catalysts are used to speed up or help along a chemical reaction. Light is helpful in the processing of film.
Magicians are not the only ones who can change one material into something completely different. Did you know that scientists, nature and even you can change one material into another? We call this “magic” a chemical reaction.
In a chemical reaction matter is changed from one substance from one to another.
Burning wood changes the wood into ash. Water will react with iron to form a new product. Do you know what it is? If you have ever left your bicycle in the rain you probably know it is called rust.
Chemical reactions may also produce heat, light, bubbles or color changes. When the bike rusted, the metal turned a different color so we know that a chemical reaction occurred between the bike and the water. Please remember that not all color changes prove that a chemical reaction has taken place.
A physical change is different than a chemical change. Things that are changed physically do not turn into something else.
Breaking a match in two pieces is an example of a physical change. Lighting a match and letting is burn is an example of a chemical change.
Matter undergoes certain changes as a result of the application of energy. Glaciers melt in summer and rivers freeze in winter. Water from saltpans on the sea coast dry up, leaving behind salt. Water from the sea evaporates to from water vapor, which form into clouds and then condense to form rain. A candle upon burning gives light, heat, water vapor and carbon dioxide. Hydrogen burns in air to form water.
Physical Change
A physical change is one in which the shape, size, appearance or state, of a substance may alter, but its chemical composition remains same. No new substance is formed. It is usually a change, which is reversible. By reversing the process, the original substance can be obtained.
Chemical Change
A change in which the composition of a substance is altered is called as chemical change. As a result, the original properties get changed and one or more new substances are formed.
Main Features of Physical and Chemical Changes
Energy Changes in a Chemical Reaction
Chemical reactions are often accompanied by evolution or absorption of energy.
Types of Chemical Changes
Decomposition It is a chemical reaction in which molecules of a substance break down to form simpler molecules of two or more new substances. Decomposition of a substance, due to heat is called thermal decomposition, while decomposition due to electricity, is called electrolytic decomposition.
Action of Heat on Substances
Heat is a very powerful form of energy. Although there are other forms of energy like light and electricity, heat is the most commonly used agent for initiating all chemical changes.
Summary
In a physical change the shape, size, appearance or state of a substance may alter, but it is a temporary change, which is usually reversible. There is no new substance formed, no change in the mass of the substance and no energy changes are involved.
Matter is the Stuff Around You
Mixtures on Earth Matter is everything around you. Matter is anything made of atoms and molecules. Matter is anything that has a mass. Matter is also related to light and electromagnetic radiation. Even though matter can be found all over the universe, you usually find it in just a few forms. As of 1995, scientists have identified five states of matter. They may discover one more by the time you get old.
You should know about solids, liquids, gases, plasmas, and a new one called Bose-Einstein condensates. The first four have been around a long time. The scientists who worked with the Bose-Einstein condensate received a Nobel Prize for their work in 1995. But what makes a state of matter? It's about the physical state of molecules and atoms.
Changing States of Matter
Sun has more matter than all planets Elements and compounds can move from one physical state to another and not change. Oxygen (O2) as a gas still has the same properties as liquid oxygen. The liquid state is colder and denser but the molecules are still the same. Water is another example. The compound water is made up of two hydrogen (H) atoms and one oxygen (O) atom. It has the same molecular structure whether it is a gas, liquid, or solid. Although its physical state may change, its chemical state remains the same.
So you ask, "What is a chemical state?" If the formula of water were to change, that would be a chemical change. If you added another oxygen atom, you would make hydrogen peroxide (H2O2). Its molecules would not be water anymore. Changing states of matter is about changing densities, pressures, temperatures, and other physical properties. The basic chemical structure does not change.
The properties of a substance are those characteristics that are used to identify or describe it. When we say that water is "wet", or that silver is "shiny", we are describing materials in terms of their properties. Properties can be divided into the categories of physical properties and chemical properties. Physical properties are readily observable, like; color, size, luster, or smell. Chemical properties are only observable during a chemical reaction. For example, you might not know if sulfur is combustible unless you tried to burn it.
Another way of separating kinds of properties is to think about whether or not the size of a sample would affect a particular property. No matter how much pure copper you have, it always has the same distinctive color. No matter how much water you have, it always freezes at zero degrees Celsius under standard atmospheric conditions. Methane gas is combustible, no matter the size of the sample. Properties, which do not depend on the size of the sample involved, like those described above, are called intensive properties. Some of the most common intensive properties are; density, freezing point, color, melting point, reactivity, luster, malleability, and conductivity.
Extensive properties are those that do depend on the size of the sample involved. A large sample of carbon would take up a bigger area than a small sample of carbon, so volume is an extensive property. Some of the most common types of extensive properties are; length, volume, mass and weight.
Pieces of matter undergo various changes all of the time. Some changes, like an increase in temperature, are relatively minor. Other changes, like the combustion of a piece of wood, are fairly drastic. These changes are divided into the categories of Physical and Chemical change. The main factor that distinguishes one category form the other is whether or not a particular change results in the production of a new substance.
Physical changes are those changes that do not result in the production of a new substance. If you melt a block of ice, you still have H2O at the end of the change. If you break a bottle, you still have glass. Painting a piece of wood will not make it stop being wood. Some common examples of physical changes are; melting, freezing, condensing, breaking, crushing, cutting, and bending. Special types of physical changes where any object changes state, such as when water freezes or evaporates, are sometimes called change of state operations.
Chemical changes, or chemical reactions, are changes that result in the production of another substance. When you burn a log in a fireplace, you are carrying out a chemical reaction that releases carbon. When you light your Bunsen burner in lab, you are carrying out a chemical reaction that produces water and carbon dioxide. Common examples of chemical changes that you may be somewhat familiar with are; digestion, respiration, photosynthesis, burning, and decomposition
A physical change is reversible, a chemical change is not. For example, the freezing of water would be a physical change because it can be reversed, whereas the burning of wood is a chemical change - you can't 'unburn' it, A physical change is a change in which no new substance is formed; a chemical change results in the formation of one or more new substances. Again, consider the previous examples: Freezing water into ice just results in water molecules which are 'stuck' together - it's still H2O. Whereas burning wood results in ash, carbon dioxide, etc, all new substances which weren't there when you started
Is there a difference?
Yes, is a big difference! If you change something physically you still have what you started with. For example, if you tear a piece of paper you still have paper. If you change something chemically you end up with something very different than what you started with. For example if you burn a piece of paper you end up with carbon and no more paper.
But, these are obvious examples. Is it always that simple? What if you put sugar into water? Is that a physical or a chemical change? How about if you freeze water? Is that physical or chemical? For these examples we have to examine what it would take to get the original substances back after wo have made the change. With the sugar and the water we could evaporate the water and find that the sugar is left and there is no change, except in how it looks. It is still sweet and it can be remixed in water. The frozen water can be melted and we have the same water we started with.
If we take that same sugar and water and mix it with flour and eggs and vanilla and chocolate chips and cook it we will have performed a chemical change making cookies. No matter what you do to the cookies you will never get the sugar and the water out of them as before.
All substances have properties that we can use to identify them. For example we can idenify a person by their face, their voice, height, finger prints, DNA etc.. The more of these properties that we can identify, the better we know the person. In a similar way matter has properties - and there are many of them. There are two basic types of properties that we can associate with matter. These properties are called Physical properties and Chemical properties..
Physical properties: Properties that do not change the chemical nature of matter
Chemical properties: Properties that do change tha chemical nature of matter
Examples of physical properties are: color, smell, freezing point, boiling point, melting point, infra-red spectrum, attraction (paramagnetic) or repulsion (diamagnetic) to magnets, opacity, viscosity and density. There are many more examples. Note that measuring each of these properties will not alter the basic nature of the substance.
Examples of chemical properties are: heat of combustion, reactivity with water, PH, and electromotive force.
The more properties we can identify for a substance, the better we know the nature of that substance. These properties can then help us model the substance and thus understand how this substance will behave under various conditions.
Physical properties:
Colour
Melting Point
Boiling Point
Solubility
Hardness
Strength
Elasticity
Heat Conductivity
Electrical Conductivity
Ability to transmit light
Lustre ('shininess' or dullness)
Magnetic attraction
Chemical Properties are:
pH
Reaction with oxygen (flammability or corrosion)
Reaction with water
Reaction with acids and bases
Reaction with metals
So, in summary, there are really only two criteria for whether a change is chemical or physical: After the change does it look the same and Can you change it back? If the answer is yes, the change is physical every time.If the answer is no the change is chemical every time.
How many pages is this in microsoft word?
It is 5 pages long
Reply:5 pages
Reply:Typed exactly like that...four and three quarters of a page.
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