need a lot of help on compounds/mixtures, hetero/homoegeneous, colloids/suspensions, physical/chemical help!!!

Question

huge test tomorrow!!
need help with telling the difference between compounds, mixtures, solutions, heterogeneous
physical and chemical reactions and noticing them
colloids/suspensions
and chemical and physical properties
teacher is awfula nd doesn't explain anything please help i am going to fail!

Answer 1

In chemistry, you start with elements. Elements are "indivisible". Then you have compounds which are two or more elements combined. They can be seperated by chemical means (i.e. chemical reactions that liberate one element).

Mixtures are combination of two or more compounds or solutions that are easy to seperate. Mixtures can generally be seperated by physical means like boiling, sieving, and so on.

Solutions are a combination of solvent and solute. In this case, a chemical reaction occurs and so solutions cannot be seperated by physical means but chemical means only.

A homogeneous solution/ mixture is uniform throughout. For example, water mixed with table salt (sodium chloride) would be homogeneous solution.

A heterogeneous solution/mixture is not uniform. For example, water mixed with oil will be heterogeneous because oil does not dissolve with water and collects on top of the water (an the interface).

I am not sure what is meant by physical reaction. There is generally only a chemical reaction which occurs when two solutions are combined or a solution and some solid is combined. A chemical reaction can be noticed by changes that occur in your beaker or other container such as production of gas (bubbles) or change in color (change to magenta when phenolphthalein is indicator in acid/base reactions and basic conditions have been reached).

Colloids and suspensions are alike. Colloids are solutions with tiny solid particles distributed throughout. They are generally homogeneous looking and will not settle easily because of motion of the tiny particles (it is called Brownian motion but you probably haven't studied that yet right?).

Suspensions are generally solutions that contain larger particles than colloids. If a suspension is left out for some time, larger particles will settle at the bottom of the container.

Lastly, physical properties are things like mass, temperature, volume and so on. They are measurable and related to the materials we are studying.

Chemical properties are things like phase, state, pH, and so on. They are related to chemistry of the system and contents of the system. Like pH is dependent on amount of hydronium ions you have in a solution.

Answer 2

Compounds: contain two or more pure substances and need a chemical process to seperate the constituents.
Mixtures, on the other hand contain two or more substances, but can be separated by physical techniques as simple as handpicking, filteration, etc.
Solutions: Contain a solvent and at least one solute. The solute is the one which is present in a lower amount.
Heterogeneous: Hetero means "not uniform". A good example is sand in water. You clearly see sand and water as sand does not dissove in water. Homogeneous is "uniform", where you cannot see the contents with naked eye. Sugar solution and any solution is homogeneous.
Physical changes are reversible - melting and boiling.
Chemical changes are irreversible.
Colloids and suspensions differ in particle size. Refer the book for exact particle sizes.
Chemical properties are the properties which explain the REACTIVITY of the substance with other and tendancy of the substance to become another. It ultimately is based on the electronic structure of the element/compound.
Physical properties are properties like appearance, melting point, boiling point, vap pr., etc.

Hope this helps you start off.
Go through your text for EXACT definitions.

Answer 3

A compound is the result of 2 or more elements that are chemically combined. An example of a compound is water. It is a combination of hydrogen and oxygen. A mixture is a combination of 2 elements that are physically combined and can be separated.
A homogeneous mixture is a mixture wherein the objects in the mixture cannot be distinguished. A heterogeneous mixture is a mixture wherein the objects that are combined can still be distinguished.

Answer 4

Chapter 2.

Compounds are made of pure substances in fixed proportions.
Physical changes are usually reversible and are based on physical properties (density, viscosity, melting point, boiling point, maleability). Chemical changes are not reversible and are based on chemical properties (flamability and reactivity).

That should get you half way. Your textbook should cover this material.

Answer 5

homogeneous means uniform composition
hetreogeneous means nonuniform composition
Egs-homogeneous-sugar in water ,salt in water, water and alcohol etc...
heterogeneous-wood, blood,sand and salt etc....

Answer 6

Shouldn't it be in your textbook?

Answer 7

dude, one word...cram.

Answer 8

http://en.wikipedia.org/wiki/Chemical_compound

http://en.wikipedia.org/wiki/Mixture

http://en.wikipedia.org/wiki/Solution

http://en.wikipedia.org/wiki/Heterogeneous#Chemistry

http://en.wikipedia.org/wiki/Chemical_reactions

http://en.wikipedia.org/wiki/Colloids

http://en.wikipedia.org/wiki/Suspensions

I'd give these a try...