Grade 9 Chemistry Unit Science 9 Curricular outcomes: 307-12, 307-13, 307-14, 307-15, 307-16 http://www.gov.pe.ca/photos/original/ed_gr9_sciguide.pdf
Chemistry • Chemistry is the part of Science that depends directly on particle theory.
The definition of matter • Matter is anything that has a mass, has a volume and is made of tiny particles called atoms (this is why matter has a mass in the first place). • Energy is not matter because it is not made of atoms. • ***Modern Science connection: what is « dark matter »?***
The properties of matter • All matter has 4 physical properties in common: • All matter is made of atoms. • All matter has masse (measured in grams or kilograms) • All matter has volume (measured in milliliters, liters or cubic centimeters (cm3) • All matter has a particularly defined state at room temperature (between 20 and 25 ºC)
The states of matter (9th grade) • There are 3 states of matter: • Solid • Liquid • Gas
The states of matter (overall) • Overall, there are really 5 states of matter: • The Bose-Einstein Condensate ****** • Solid • Liquid • Gas • Plasma ******
Particle Theory of Matter • Particle Theory of Matter is a scientific model that explains the behavior of any matter existing in in the Universe. • Behavior of matter basically means the different states of matter in which matter can exist. • You learned about particle theory in Grades 7 and 8.
The 4 parts of the Particle Theory of Matter • All matter has atoms (small particles) • Any bit of matter that is considered a pure substance has only 1 type of particle (this could be an atom or a molecule) • The particles in matter are always moving and are able to attract other particles (this is the basics of gravity). • If you change matter’s temperature, the movement of the particles change because their energies are changing. A particle’s increase or decrease in movement speed leads to matter changing from one state to another. If you increase matter’s temperature (i.e. heat matter up), the particles within it move faster because the particles’ energy is increasing. The opposite action is also true---a decrease in temperature will make particles move slower.
A simple way of classifying matter (7th grade) • All matter can be classified simply into 2 large categories: • Mixtures • Pure Substances
Mixtures and Pure Substances • A pure substance has only 1 type of particle (an atom or a molecule) • A mixture has at the very least 2 types of particles (an atom or a molecule)
Another simple way to classify matter: • All matter can also be classified simply as: • Homogeneous substances • Heterogeneous substances
Homogeneous Substances • A homogeneous substance is a substance that has a uniform composition (only 1 thing is visible) • Pure Substances and Solutions (or alloys) can be homogeneous substances. • Examples of homogeneous substances are water, salt, iron, plastic etc
Heterogeneous Substances • A heterogeneous substances is a mixture that does not have uniform composition (more than 1 thing is visible) • For example, a garden salad is a heterogeneous substance.
How to determine a homogeneous substance from a heterogeneous substance • Transparency is a property of a homogeneous substance. • As well, you can only see 1 thing in a homogeneous substance. • Lack of transparency and seeing more than 1 different thing can help indicate if something is a heterogeneous substance.
The types of mixtures • There are 2 types of mixtures: • Solutions (homogeneous mixtures) • Mechanical Mixtures (heterogeneous mixtures)
A solution • A solution is a homogeneous mixture made of 2 or more different pure substances. • The particles in a solution are very small and scattered equally in all directions (uniformly) • Solution examples: a drink of Kool-Aid, salt water, flat pop etc.
The parts of a solution • The substance that dissolves the solute to make a solution is called the solvent (typically a liquid but can be a gas or a solid) • The solute is the substance that is dissolved in the solvent (typically a solid but can be a liquid or a gas)
Dissolving • Dissolving a solute in a solvent is a physical change because it is reversible (the 2 materials can be separated from each other if necessary)
Alloys • An alloy is a solid homogeneous mixture that has 1 or more metals within it. • An alloy is an example of a solid solution.
Alloy examples • Various types of steel • Tin • Various coins (cupronickel, etc.) • Bronze • Brass
Mechanical Mixtures • A mechanical mixture is a heterogeneous substance that has more than 1 different particle/substance. • Examples: concrete, sand, regular garden salad, relish, Trail Mix, Bits n’ Bites etc.
The particles of mechanical mixtures • The particles in a mechanical mixture are big enough to be seen by one’s eyes. • The particles in a mechanical mixture are not scattered uniformly---they are randomly organized.
The categories of mechanical mixtures • There are 3 categories of mechanical mixtures: • I have them in decreasing order according to particle size. • Ordinary mixtures • Suspensions • Colloids
Ordinary mixtures • The different particles in an ordinary mixture are easy to see and always stay mixed together. • Examples of ordinary mixtures: Bits n Bites, regular garden salad, vegetable soup, etc.
A suspension • A suspension is a mechanical mixture that is made of small particles that can separate if we let the suspension settle or come to rest. • Examples of a suspension: dirt sediment in water, ketchup, mustard, natural peanut butter, balsamic vinegar salad dressing, etc.
How suspensions separate • The force of gravity is needed to separate particles that are mixed as a suspension. • However, the speed of separation is affected by the size of the particles in the suspension. If the particles in suspension are small, the separation is very slow.
A colloid • A colloid is a mechanical mixture with very small particles that are regularly scattered in other substances. • Colloids are in between solutions and heterogeneous mixtures because of this small particle size.
Colloid examples • Jello gelatin • Whipped cream • Mayonnaise • Paint • Glues • Butter • Milk
Characteristics of colloids • Colloids are heterogeneous but appear to be homogeneous. • The particles of a colloid are soo small only a microscope can see them yet they are much larger than the particles of a solution.
Can the parts of a colloid be separated by gravity? • Since the particles in a colloid are very tiny, the force of a gravity can not separate a colloid into its individual parts.
The diffusion of light by mixtures • Rays of light are normally invisible. However, if rays of light are scattered by a substance, you can see the light ray as a beam of light. (sunbeams in a cloud, etc) • Rays of light are diffused or scattered by the particles of a colloid but not by the particles in a solution. • So, this is a great way to distinguish a colloid from a solution.
The Tyndall Effect • So, the diffusion of light by the particles in a colloid is called the Tyndall Effect, named after its discoverer, John Tyndall, an Irish scientist.
Changes in matter • Changes in matter can classified into 2 categories: • Physical changes • Chemical changes
A physical change • A physical change does not make a new substance when it occurs. (it does not change the matter’s original composition so it is reversible) • An example of a physical change is melting ice.
A chemical change • A chemical change always makes a new substance when it occurs. (it changes the matter’s original composition to something different thereby creating something different) • A chemical change is irreversible or not-reversible. • An example of a chemical change is burning paper.
Indicators of a chemical change • Heat production • Heat absorption • All the initial material is used up. • Color change (either a color appearing or disappearing) • Formation of a new substance • Gas bubble formation in the liquid (fizz) • Formation of a solid precipitate in the liquid.
What is a property? • A property is a characteristic that describes matter.
Examples of a property • Color • Texture • Taste • Odor or smell • Shape • Hardness • Size
Types of properties • All matter have properties. • Properties of matter are classified into 2 categories: • A physical property • A chemical property
Physical properties • A property that can be observed without creating a new substance is a physical property. • Examples of physical properties: colour, texture, smell, taste etc.
Types of physical properties • There are 2 types of physical properties: • Qualitative physical properties • Quantitative physical properties
Qualitative physical property • A Qualitative physical property is a property of a substance that we can describe but we cannot measure with numbers. • An example of a qualitative physical property is the colour of a substance.
Quantitative physical property • A Quantitative physical property is a property of a substance that we can measure with numbers. (numerically) • An example of a quantitative physical property is the density of a substance.
Density of a substance • The density of substance is the quantity of matter that occupies a specific volume or space.
3 useful density equations • To calculate the density of a substace: Density = Mass/Volume (mv= m/V) • To calculate the mass of a substance: Mass = Volume x Density (m = V x mv ) • To calculate the volume of a substance: Volume = mass/density (V= m/ mv)
A chemical property • A property that creates a new substance when we observe this particular property in the specific substace is a chemical property. • Examples of chemical properties: combustibility, the ability of a substance to burn when in contact with air, etc.
Antoine Lavoisier • Antoine Lavoisier was a French scientist. (1743-1794) • He contributed 2 very important scientific laws in the field of Chemistry.
Antoine Lavoisier research • Lavoisier developed 2 laws of Science: • Conservation of mass Law • Law of definite proportions