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Two types of pure substances

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elements and compounds. Elements are substances that can not be broken down into simplere substances. Compounds are pure substances made from two or more elements and are chemically combined.

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Matter

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Anything that has mass and takes up space. Matter can be broken down into pure substances ( elements and compounds) and mixtures ( homogeneous and heterogeneous)

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mixture

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more than one substance present. Substances may be in different states.

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homogeneous mixtures

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substances completely mixed. Mixture exists in one state or phase.

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heterogeneous

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substances can be separated.

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elements

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building blocks of the universe. Over a hundred elements but mainly the universe 's mass consists of Hydrogen and Helium

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Earth and elements

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94 elements found naturally on Earth. Eight elements account for 98% of earth's mass. Silicon and Oxygen bound together to form silicate rocks make up 3/4 of the earth's crust.

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human body and elements

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65% oxygen; 18% carbon; 10% hydrogen, 3% nitrogen, 2% calcium, and 2% others

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Substances

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can be broken down or forced to react to form new substances. Ex: Copper carbonate( green power) when heated froms into a black power

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decompostion

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a compound breaks down to form 2 or more substances; can be brought on by electricity;

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decomposition and electricity

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Some substances do not conduct electricity when solid; however, do conduct when melted or in a solution. In the process of conduction, the substances are broken down into simpler elements. Ex: When lead bromide is melted, a current is passed and thru molten lead, bromine is formed

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synthesis

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when a substance is formed by the combination of two or more other substanced. Ex: Mg put into a jar of O, white ash remains and different properties to the original properties of Mg and O. In this case, Magnesium Oxide has formed.

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chemical reaction

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new chemical substances are formed; generally the process is not easily reversed, energy is often given out

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physical change

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usually involve melting or dissolving; substances do not change identity; can be easily changed into their orginial form using physical processes of cooling or evaporation.

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Explain the synthesis when powdered iron and sulfur are heated

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Powder glows ( even for a few minutes after the bunsen burner is removed). Heat energy is given out; product is black non magnetic solid, iron sulphide which can not be easily be changed back into iron and sulpher. This experiement shows: making a mixture of substances and forming a new compound.

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When a mixture forms

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the substances are simply mixed together, the composition of the mixture can be varied, the properties remain the same, the mixture can be separated by physical methods such as filtration, distillation, and magnetic attraction

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when a compound forms

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the substances chemically reacts to form a new compound; the composition of the new compound is always the same; the properties of the new compound are very different from the originial elements; the compound can not be easily be separted into its elements

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atomic theory

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John Dalton; 1807.
Suggested that a pure element is composed of atoms; the atoms of each element are different in size and mass; atoms are the smallest particles that take part in chemical reactions; atoms of different elements can combine to make molecules of a compound.

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kinetic theory

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all matter is made up of very small particles; the particles are moving all the time; heavier particles move more slowly than lighter particles when at the same temperature.

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gasses

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the particles are arranged irregulary; are spread far apart as compared to liquids and solids; able to move more randomly

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lattice

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highly structued ordered microscopic arrangements.

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gas and heating

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the particles move faster and liquid expands. Some particles have enough energy to escape from the surface and evaporation has taken plafce. Evaporation is faster at higher temperatures as the particles have more energy.

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boiling point

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the particles have enough energy to break the forces that attract them together; the particles move very fast and separate from each other and the liquid boils.

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liquid

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the particles are closely packed together, are in an irregular arrangement; able to move past each other.

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solids and rising temperature

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the particles vibrate more strongly, occupy more space and cause the solids to expand. Eventually, the particles have enough energy to break the forces holding the lattice together and the solid melts

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solid

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the particles are packed closely together in a regular arrangement and vibrate in their fixed position,

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inter molecular space

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the space between particle. Also known as IMS. In a gas, the IMS is large and can be reduced by increasing the external pressure. Gases are easily compressed. Liquids are not very compressible.

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Boiling

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The temperature stays constant over time ( at the same heat); the energy put in mkes the particles move faster and overcomes the forces holding the liquid together

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melting

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as the temperature stays constanct over time, the energy put in is used to overcome the lattices being held together.

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Over time and with increasing temperature

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form solid- to liquid-gas. Remember the rate of evaporation increases with temperature

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endothermic

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melting, evapoation, and boiling

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exothermic

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energy is given out; condensation and freezing are exothermic.

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a refridgerator and

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1. Fridge is controlled by a thermostat. When the temperature increases, the pump switch turns on.
2. The pump condenses the coolant ( a gas) to a liquid. This gives out energy, thus the liquid is hot.
3. The liquid is cooled down by the air outside as it passes thru the fins at the back of the fridge.
4. The liquid passes thru the fridge when it warms up and becomes a gas again. This takes in energy so the inside of the fridge is cool.

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diffusion

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involves the movement of particles from a region of higher concentration to a region of lower concentration. Eventually, the particles are evenly spread thru out. Diffusion does not take place in solids. Diffusion is much slower in liquids than in gases.

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The idea that particles in fluid in moving come from

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diffusion

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why is diffusion important

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diffusion contributes to the movement of oxygen from the lungs to the blood and the carbon dioxide from the blood to the lungs.

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Diffusion example and bromine

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Bromine liquid droplets are put into a gas jar. The brominie vaporizes the brominie gases fill in the space. In other words, the gas looks brown.

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Diffusion

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Not all gases diffuse at the same rate and is called the rate of diffusion.The Brownian motion is the seemingly random movement of particles suspended in a fluid (i.e. a liquid or gas) or the mathematical model used to describe such random movements, often called a particle theory.

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The absolute scale of temperature

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Lord Kelvin. Two imporant points:
The pressure of a gas is the result of collisions of the fast moving paticles with the walls of the container; the average speed of the particles increases with an increase in temperature.

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If the temperature of a gas in a container of fixed volume is raised

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the speed and momenturm of the particles will increase

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Absolute zero

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The point at which the particles stop moving and have no energy. Kelvin scale starts at 0 and the freezing point is 273K and the boiling point is 373K. THere is no degrees with Kelvin

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kinetic theory

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explains that gases are the least dense and by far the most compressible and lays proof to the claim that all matter is made up of small particles.

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Rate of diffusion

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the lower the molecular mass of a gas, the faster it will diffuse; hydrogen having the lightest molecules will diffuse faster than any other gas

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diatomic moleculs

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molecules consisting of 2 atoms ( i.e. Hydrogen, Oxygen, Nitrogen, and Chlorine- the element likes to be stable with 2 atoms)

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Noble gases

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Helium, Neon, Argon- like to exist as single atoms

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