Sunday 24 May 2015

Revision tasks

Here are some additional pages you might find helpful when doing your revision. Also use some of the other information on  the blog to revise.

Rock cycle revision
Rock cycle revision game
Rock cycle MCQ's
Test your knowledge - rock cycle
Test your skills rock cycle
Diamonds
Rocks

Compounds and chemical equations revision
Compounds activity

ELEMENTS AND COMPOUNDS

Elements are simple substances which cannot be split up in chemical reactions.
Atoms are the smallest particles of an element that can exist. Atoms of an element
are all the same.
Each element has its own chemical symbol. For example, the chemical symbol for
oxygen is O.
Some elements have their atoms joined to each other in small groups called
molecules. Oxygen is an example.


Compounds
Elements can join together to make compounds. A compound contains two or more
elements joined together. The name of the compound tells you the elements that are
in it. Compounds made from two elements always have a name which ends in ‘-ide’.
Many compounds exist as atoms attached to each other in small groups – molecules.


The chemical formula tells you the numbers of atoms of each element in a
compound. Each element in the chemical formula is shown by its chemical symbol.
For example:


A compound always contains the same elements in the same ratio.
The properties of a compound are different from the elements that make it up. For
example, hydrogen is an explosive gas and oxygen will relight a glowing splint but
water is a liquid which will put fires out.

Chemical reactions
Compounds can react chemically by mixing them with other chemicals, or by using
heat or electricity. You can tell that a chemical reaction has occurred if there is a
colour change or when a gas is given off.
Most chemical reactions also involve an energy change. This is usually in the form of
heat, but can also involve light being given off, for example, in burning (combustion).
In a chemical reaction a new substance is always formed. Most chemical reactions are
not easily reversed (they are irreversible).

Some chemical reactions take place just by mixing. When you make a solid by mixing
two liquids, the solid is called a precipitate.
Other chemical reactions need energy to start them off. This energy can be in the
form of heat, light or electricity. When you use energy to split up compounds they are
decomposed.
We can write word equations to show a chemical reaction. The chemicals that you
start with are called the reactants. The chemicals at the end are called the products.
For example:


Mixtures
Elements and compounds can also be mixed together. A mixture is easier to separate
than the elements in a compound. Soil, river water and sea water are examples of
mixtures that occur naturally.
Elements and compounds melt and boil at a fixed temperature. Mixtures do not have
definite melting points and boiling points.
Air is a mixture of gases – most of the air is nitrogen and oxygen. The gases in the air
can be separated by fractional distillation.

Elements, compounds and mixtures video


Minerals
Rock cycle
Three main rocks and the Rock cycle


Monday 4 May 2015

Growing Crystals Lab Assessment

Crystal growing Lab



The study of crystals and their structure is a field called Crystallography. A crystal is a solid that consists of the various atoms, or molecules being arranged in a uniform repeating pattern based on its unique shape. This results in the material having a specific shape and colour, and having other characteristic properties. Crystals may be big or little, but they all have the same "shape". Table salt is NaCl and has a cube-shaped structure. Snow crystals form a six-sided structure. 

How are crystals grown?

In a solution, a solvent (water) can only hold a certain amount of solute. This is called the solubility of a solution. When the temperature of the solution is increased, hot water can dissolve more solid substance than cold water. This is because heated water molecules move farther apart, making room for more solid substance to dissolve. When no more of the solid substance can be dissolved, the solution is said to be saturated. As this solution cools, the water molecules move closer together again and there's less room for the solution to hold onto as much of the dissolved solid.
Crystals begin to form and build on one another as the water lets go of the excess solute. This process is called recrystallization and, depending upon conditions, one may obtain a mass of many small crystals or one large crystal.
Sourced from http://nobel.scas.bcit.ca/debeck_pt/science/crystals/crystals_p1.htm

What can affect the crystal growth?

There are a number of different things that can affect crystal growth such as:
Saturation of the solute
Changing the temperature the crystals grow in
Method to grow the crystals
The chemical used to grow the crystal

Related links


Crystal - A crystal is a solid with a definite geometric shape. The shape consists of smooth, flat surfaces that meet in sharp edges or corners.

Crystallography - A branch of Chemistry that studies crystals and their structure.
Recrystallization - Recrystallization is a process that has been used to purify solid material by dissolving the solid substance in an appropriate liquid and then having the material come out of solution in crystalline form.

Saturated solution - Solution where the maximum amount of solutes is dissolved in the solvent.
Solubility - The maximum amount of solute that can be dissolved in a certain volume of solvent at a given temperature is known as the solubility of the solute. The solubility of the solute usually increases with an increase of temperature.
Solute - Dissolved substance in a solution.

Solution - A uniform mixture of two or more substances. For example, sugar dissolved in water is a solution.
Solvent - The liquid into which the solute is dissolved. The solvent of choice in this lab is water.


Wednesday 22 April 2015