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Copy of Copy of Copy of PROJECT IN SCIENCE (FIRST GRADING PERIOD)
Transcript of Copy of Copy of Copy of PROJECT IN SCIENCE (FIRST GRADING PERIOD)
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The solvent does the dissolving. The solution more or less takes on the characteristics of the solvent including its phase, and the solvent is commonly the major fraction of the mixture. The concentration of a solute in a solution is a measure of how much of that solute is dissolved in the solvent.
A solution in which the maximum amount of solvent has been dissolved. Any more solute added will sit as crystals on the bottom of the container.
A heterogeneous mixture is made of different substances that remain physically separate. Heterogeneous mixtures always have more than one phase (regions with uniform composition and properties).
Example:Water and Sand
A homogeneous is a mixture where the components that make up the mixture are uniformly distributed throughout the mixture.
Example:Powdered juice mix in water
A pure substance is a sample of matter with both definite and constant composition with distinct chemical properties.
What is an Element?
An element is a substance consisting of atoms which all have the same number of protons - i.e. the same atomic number.
Elements are chemically the simplest substances and hence cannot be broken down using chemical methods. Elements can only be changed into other elements using nuclear methods.
Elements are the simplest form of matter.
An ionic bond is a chemical link between two atoms caused by the electrostatic force between oppositely-charged ions in an ionic compound.
Examples: There is an ionic bond between the sodium and chloride ions in table salt.
A compound is a substance formed when two or more chemical elements are chemically bonded together.
Two types of chemical bonds common in compounds are covalent bonds and ionic bonds.
The elements in any compound are always present in fixed ratios.
Example 1: Pure water is a compound made from two elements - hydrogen and oxygen. The ratio of hydrogen to oxygen in water is always 2:1. Each molecule of water contains two hydrogen atoms bonded to a single oxygen atom.
Example 2: Salt is a compound made from 2 elements - sodium and chloride
Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most (valence) electrons, atoms can fill up their outer electron shell and gain stability. Nonmetals will readily form covalent bonds with other nonmetals in order to obtain stability, and can form anywhere between one to three covalent bonds with other nonmetals depending on how many valence electrons they posses. Although it is said that atoms share electrons when they form covalent bonds, they do not usually share the electrons equally.
Acids and Bases
You can tell it by the indicator,a dye that changes into a different color depending on whether it is acidic or basic and by the use of litmus paper,a dye taken from the lichen plant.Litmus turns red in acidic mixture and blue in basic mixture.
How can you tell if a mixture is Acidic or Basic?
Effect of acid in metals
The main effect would be corrosion, which weakens more reactive metals such as iron much faster than less reactive metals such as gold.
Non - metals
One of the elements which do not exhibit metallic properties, generally located in the upper righthand corner of the Periodic Table.
Example: oxygen, sulfur
A substance with high electrical conductivity, luster, and malleability, which readily loses electrons to form positive ions (cations). Metals are otherwise defined according to their position on the Periodic Table, including groupings as alkali metals, alkaline earth metals, transition metals, and rare earth metals.
Example: copper and iron
Metals can conduct electricity
Metals have the peculiar characteristic of having free electrons in the atomic structure. These electrons are then free to move and convey an electric current.
Example: copper and gold
Diversity of materials in the environment
An unsaturated solution has a low concentration of the solute dissolved in it. An unsaturated solution has room for additional solute to be added and fully dissolved, without settling and sedimentation occurring. This makes a comparatively weak solution when compared with a saturated one.
By:Francess Dea Balane-Grade 7 - Anthracite
Independent and Dependent Variable
Independent variables - The values that can be changed in a given model or equation. They provide the "input" which is modified by the model to change the "output."
Dependent variables - The values that result from the independent variables.
Example of Variables in Scientific Experiments
If a scientist conducts an experiment to test the theory that a vitamin could extend a person’s life-expectancy, then:
The independent variable is the amount of vitamin that is given to the subjects within the experiment. This is controlled by the experimenting scientist.
The dependent variable, or the variable being affected by the independent variable, is life span.
This is controlled by the experimenting scientist.
The dependent variable, or the variable being affected by the independent variable
Example of Variables in Mathematics
In mathematics, the "x" and "y" values in an equation or a graph are referred to as "variables."
If an equation shows a relationship between x and y in which the value of y is dependent upon the value of x, y is known as the dependent variable and is sometimes referred to as ‘function(x)’ or f(x).
The final solution of the equation, y, depends on the value of x, the independent variable which can be changed.