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Terms to know• Chemical property- the way a substance reacts
with others to form new substances.• Reactivity- ability of a substance to combine
chemically with another substance.• Physical property- characteristic of a substance
that can be observed or measured without changing the composition of the substance.
• Melting point- temperature at which a solid becomes a liquid.
• Boiling point- temperature at which a liquid becomes a gas.
• Freezing Point – the temp. a liquid becomes a solid
Terms to know
• Buoyancy- force with which a more dense fluid pushes a less dense substance upward.
• Chemical change- change that occurs when a substance changes composition by forming one or more new substances.
• Physical change- change in the physical form or properties of a substance that occurs without a change in composition.
Matter• Anything that takes up space and
has mass.• Matter can have physical and
chemical properties• Physical properties: density,
melting points, boiling points, freezing points, colors or smells.
• Chemical properties: the way an element combines with others.
States of matter
• Four main states of matter– Solid– Liquid– Gas– Plasma
• Matter may change “phases” when physical forces are present– Example: temperature causes matter
to move to a more excited state
If energy is added or taken away, matter changes
phases
Solids
Solids can be composed of many different thingsFor example: mixtures, different
elements, or compounds.Solids hold their own shapeAtoms inside a solid are not
allowed to move around a lot- they are trapped inside their spaces
When does a liquid become a solid?
• Freezing point is the point at which a liquid becomes a solid.
• Many factors affect freezing points:– Temperature– Pressure- easier to freeze at higher
temps.
Liquid Basics
• Liquids are an in-between phase (between solid and gas)
• Liquids fill the shape of a container
• Liquids are hard to compress (atoms are already so close together)
Becoming a liquid
• When a solid reaches it’s melting point, it becomes a liquid. It just needs energy (heat)
Becoming a liquid• For a gas to become liquid, it
needs to lose energy. How?• Easy- lowering the temperature
allows atoms to move slower, thus settling down allowing it to reach it’s condensation point.
• Gas becomes a liquid at it’s condensation point.
Evaporation
• Liquid may undergo evaporation and become a gas.
• All liquids can evaporate at room temperature and pressure.
• What is evaporation?– Evaporation is when
atoms escape the liquid and become a gas.
Gas• Gases are random groups of atoms.
• Gases contain a lot of energy; atoms are in constant motion
• Atoms in gases are really spread out
• Gases can fill a container of any size or shape- atoms and molecules spread out evenly
Becoming a gas…
• Becoming a gas needs energy (temperature increase)
• When energy is added, the atoms become excited
Plasma
• Plasma is like a gas, but the atoms are made up of free electrons and ions.
• Plasmas are not common on Earth, however you may have seen plasma.– Northern lights or lightning
Becoming plasma
• When electrons are stripped from atoms, what is left is negative and positively charged particles (ions)
• When ions are in equal concentrations, the charge is neutral.
• Lots of energy is needed to change a gas into plasma.
Becoming plasma
• Adding large amounts of energy causes the neutral atoms to break apart into positive and negative charged ions and free electrons
• Leaving electrons and ions is a gaseous ball!
Mixtures• Substances held together by
physical forces. • Mixtures are all around us- oceans,
rocks, tap water… everywhere!
Just H2O molecules
Tap waterhas other substances dissolved in it
If you boiled the tap water, you would have the dissolved substances left over (salt for example). Salt would maintain it’s own properties.If you wanted to boil away salt you would need higher temps.
Mixtures
• Substances in mixtures can always be separated by physical means.
– Example: mixture of sand, salt and water – How would you separate the substances?
Solutions
• Solutions are groups of molecules that are mixed up in a completely even distribution.– Homogenous (homo = same)
Example: Sugar dissolved in water is evenly distributed as in kool-aid.
Solutes, Solvents, Concentration
• A solution is two substances combined• Solute is what is being dissolved• Solvent is what is doing the dissolving
• Solubility is the ability of the solvent to dissolve the solute.
• What is the universal solvent?
Additional Terms to Know•Metals – shinny luster, malleable, ductile, good conductors of electricity and heat. Left of zig-zag line.•Non-metals – dull, brittle, non-conductors of electricity and heat, at room temperature most are gases. Right of zig-zag line.•Inert gases: Last column of periodic table, will react with no other elements.•Carbon-12: carbon with a mass of 12, the bases for the periodic table and all other elements are compared to.•Avagadro Number: amount of atoms or molecules of a substance in 1 mole of the substance.( 6.02 X 1023)•Mole: amount of substance equal to it’s atomic weight in grams.• ex: 1 mole sodium = 23 grams, 1 mole of zinc 65 grams, 1 mole of H2O = 18 grams. 2 moles = 2 X atomic wt. .25 moles = .25 X atomic wt., etc.•Inertia – Newton’s 1st Law of Motion: a body will stay at rest or in motion until an outside force acts upon it.•Exothermic – release of energy, all ionically bonded reactions are exothermic.•Endothermic – absorption of energy, most covalently bonded reactions are endothermic but some are exothermic.•Catalyst – a substance used in a chemical reaction to change the rate of the reaction without itself being used up.
More terms
• Period or Series – Horizontal row of elements. Numbers and letter correspond to the shells and energy level you find the valance electrons in.
• Group or Family – Vertical column of elements excluding the transition metals.
• Zigzag line – line separating metals form the non metals.
• Metalloids – elements with characteristics of both the metals and non-metals. Touching the zigzag line with one full side.
