notes 2-1 describing matter. matter anything that has mass and takes up space substance- single...
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Matter
Anything that has mass and takes up space
Substance- single kind of matter that has a specific make-up and specific properties
-Example: Salt or sugar
-Non-Example: Muffin batter (the ingredients can vary)
Physical Properties of Matter
Can be observed without changing into another substance
Examples: Freezing point, melting point, density, texture, color, flexibility, solubility in water
Chemical Properties of Matter
Ability to change into a different substance
Examples: flammability, rusting, tarnishing, rising of bread in baking process
Elements
Pure substances that cannot be broken down into any other substance
Simplest substances
Is identified by its specific physical and chemical properties
Examples: Carbon, Oxygen, Gold, Silver, Aluminum
Atoms
Basic particle that makes up all elements
Having different atoms gives elements their unique properties
Atoms have a nucleus made up of positively charged protons and neutrally charged neutrons, and they are surrounded by a cloud of negatively charged electrons
Modeling an Atom
Pencil “lead” is made of mostly graphite, a form of carbon. Two ways to model atoms used in this presentation are shown here for carbon.
Chemical Bonds
Atoms combine by chemical bonds (a force of attraction between the electrons of 2 or more atoms)
Often form molecules- groups of 2 or more atoms held together by chemical bonds
Examples: H2O, O2, CO2
Compounds
Pure substance made up of 2 or more elements chemically combined in a set ratio
Represented by a chemical formula which shows the elements in the compound and the ratio of atoms
When elements combine to form compounds, they have unique properties from those of the uncombined elements
-Example: Hydrogen alone is a very combustible gas, Oxygen alone is a major supporter of combustibility, but when combined in the set 2:1 ratio H2O, they put out fires!
Ratios
A ratio compares two numbers. It tells you how much you have of one item compared to how much you have of another. For example, a cookie recipe calls for 2 cups of flour to every 1 cup of sugar. You can write the ratio of flour to sugar as 2 to 1, or 2:1.
The chemical formula for rust, a compound made from the elements iron (Fe) and oxygen (O), may be written as Fe2O3. In this compound, the ratio of iron atoms to oxygen atoms is 2:3. This compound is different from FeO, a compound in which the ratio of iron atoms to oxygen atoms is 1:1.
Ratios Practice Problem
What is the ratio of nitrogen atoms (N) to oxygen atoms (O) in a compound with the formula N2O5? Is it the same as the compound NO2? Explain.
N2O5 contains two nitrogen atoms for every five oxygen atoms. Both N2O5 and NO2 are made up of only nitrogen atoms and oxygen atoms. However, the two compounds are different because NO2 contains one nitrogen atom for every two oxygen atoms.
Mixtures
Made up of 2 or more substances that are not chemically combined
Differ from compounds because they do not have to have a set ratio, and each substance in mixture keeps its individual properties
Examples: Air, Soil, Salt water
Heterogeneous Mixtures
Hetero = different
Can see different parts of mixture
Examples: Soil, Salad
Who can think of other examples?
Homogeneous Mixtures
Homo = same
Can’t see different parts of mixture, evenly mixed
Examples: Sugar/water solution, Air
Who can think of other examples?
Separating Mixtures
Compounds are hard to separate
Mixtures are easy to separate since each component keeps its own properties
Look at figure 10 on page 66, it shows different ways to separate a mixture including using a magnet, filtering, distilling, and evaporating
LET’S REVIEW!!
What are some examples of chemical properties of matter?
Rusting, flammability, bread baking
What are some examples of physical properties of matter?
Density, melting, freezing, color, flexibility, hardness