# What is matter Matter is anything that takes

• Slides: 65

What is matter? • Matter is anything that takes up space and has mass. • Write some examples of matter in this room… • Matter can have many different properties (characteristics that can be used to identify and classify it)

solids shape • A solid has a definite _______ and _______ volume – (“Definite” means you can tell what it is & it is the same) • A solid keeps its shape and volume no matter what it’s in • The particles are closely packed together • The particles do move some: they vibrate in place, but do not move other than that

liquids volume • A liquid has a definite _______ but not a definite ______ shape – The shape of a liquid changes with its container • Particles in a liquid still touch but move freely past each other • Liquids are fluids (a fluid is something that flows)

Properties of liquids • Water molecules are strongly attracted to each other • Surface tension: an inward force that pulls liquid molecules together, forming puddles or drops – Surface tension makes the surface of water act kind of like a skin, so things can float on (and even walk on) water • Viscosity is a liquid’s resistance to flowing (how slowly it flows) – Viscosity depends on the size and shape of the liquid’s particles – Different liquids have different viscosities • Examples: water flows differently than honey because they have different viscosities

Non-newtonian Fluids • ketchup • Ants • Mytbusters walk on water • Oobleck on a speaker in slo mo

gases • Gases have NEITHER a definite shape NOR a definite _____________ volume • In a closed container, gas particles expand to fill it • Gases are also fluids because they flow

Properties of gases • Volume: amount of SPACE matter takes up • The Volume of a gas is the same as the volume of its container • Most of the volume of a gas is empty space • Gases can be compressed (squished) to fill smaller volumes (compressed air is used to fill balloons) – When a gas is compressed, the particles do not change size, they just move farther away from each other

Properties of gases • Temperature: a measure of the average SPEED of random motion of particles • The Faster particles are moving, the more ENERGY/HEAT they have and the higher their TEMPERATURE • The particles of gases move the fastest of all the states

melting • Changing state from solid liquid • Pure, crystalline solids melt at specific temperatures called melting points • This is a physical property • The melting point of water is 0 degrees Celsius (32 deg. F) – It stays at 0 degrees until it is done freezing • As a solid melts, its particles begin to move more, and they break away from their fixed positions and can move more freely

freezing • Liquid solid • Reverse of melting • At the freezing point, particles move so slowly they start to get stuck in a fixed position – Particles lose energy • Some things become solid (freeze) at relatively high temps – Ex: chocolate, candle wax, butter

vaporization • Changing state from liquid to gas is called vaporization • This happens when the particles in the liquid gain enough energy to move independently (become a gas) • 2 types of vaporization: evaporation & boiling

evaporation • Evaporation is vaporization that takes place on the surface of a liquid • Can take place at any temperature • Ex: shrinking puddle

boiling • Boiling is vaporization that takes place all over the liquid • Forms bubbles below the surface that rise and escape • Temperature at which a liquid boils is its boiling point • Happens faster than evaporation

condensation • Changing state from a gas liquid • Opposite of vaporization • Occurs when particles of a gas lose enough energy to become liquid • Ex: breathing on a mirror, glasses fogging up, clouds forming (water vapor condensing into liquid droplets—true water vapor is invisible)

sublimation • When particles in a solid gain enough energy to turn into a gas (skip the liquid phase) • Happens on the surface (like evaporation does) • Ex: dry ice (solid CO 2), snow disappearing without forming puddles first, old ice cubes getting smaller • Opposite of sublimation is gas solid and is called deposition

Properties of matter • Used to identify and classify matter. • What are some examples of properties of matter? – Temperature, color, texture, phase (solid/liquid/gas), flammability, etc. • Chemistry is the study of matter and how it changes. • A substance is made of pure matter. It is a single kind of matter and always has the same composition (makeup). – Example: table salt, pure water

Physical Properties of matter • Matter has physical properties and chemical properties. • A physical property is a characteristic that can be observed without changing the substance into another substance. – Examples? – Luster (shininess), hardness, texture, color, temperature, conductivity (of heat or electricity), solubility, flexibility (malleability or ductility), freezing point, boiling point, melting point, size (area/length/mass/volume/etc. ), brittleness, concentration, density, electrical charge, location, luminance, momentum, opacity, specific heat, velocity, etc. .

Chemical properties • A chemical property describes the ability of a substance to change into something else. – Examples? – Reactivity, flammability, toxicity, half life • Why is freezing point a physical property and not a chemical property? ? – Because when something changes state it is still the same substance

Changes in Matter

Physical Changes • A physical changes the form (shape) or appearance of matter but NOT what it is made of – It is still the same substance – Physical changes change physical properties and do NOT change chemical properties • Examples of physical changes? – Crushing, dissolving, bending, tearing – Any changes of state/phase (boiling, melting, evaporating, etc. )

Chemical Changes • A chemical change is a chemical reaction in which one or more substances (REACTANT(S)) transform into something new (PRODUCT(s)) – Atoms are rearranged – The product(s) has different chemical properties from the reactant(s) – You can only reverse a chemical change by doing another chemical change

Chemical Changes • Examples of chemical changes? – Photosynthesis, combustion, decomposition, fermentation, rusting/oxidation, cooking, tarnishing, and any other chemical reaction

Physical or Chemical Change?

Law of Conservation of Mass • In a chemical change, the mass of the products ALWAYS equals the mass of the reactants – This is called the Law of Conservation of Mass • Matter is NEVER created or destroyed— atoms are only rearranged

Video

Endothermic Changes • (Or endothermic reactions) • Endo = inside • A chemical change in which energy is absorbed – Makes surroundings cooler • Examples? – Instant ice pack, ice melting (ice + energy = water)

Exothermic Changes • Or exothermic reactions • Exo = outside • A chemical change that releases energy – Makes surroundings warmer • Examples? – Combustion – Instant hand warmer

Solubility • Solubility is a physical property that describes how well a substance can dissolve in something else • The substance being dissolved is the solute • The substance doing the dissolving (that the solute is dissolved in) is the solvent • Water is a “universal” solvent because most things will dissolve in it

Factors affecting Solubility 1. Temperature of solvent – Solutes usually dissolve better in hot solvents – Ex: hot cocoa; ice vs. hot tea

Factors affecting Solubility 2. Surface area of solute – Powders usually dissolve better than large chunks – Ex: sugar cubes vs. granulated sugar

Factors affecting solubility 3. Stirring –Stirring helps a solute dissolve faster

Types of solutions • Unsaturated: more solute can still be dissolved • Saturated: the solvent has as much solute as it can hold • Supersaturated: the solvent contains more solute than its capacity

Solubility curves • Solubility curves are graphs of temperature vs. amount of solute • They show many grams of a substance can be dissolved in water at different temperatures • On the line = saturated • Above the line = supersaturated • Below the line = unsaturated (more solute can be added)