ENERGY & MATTER Chapter 2

Kinetic Energy (KE) Energy due to motion KE = ½ mv 2 Unit KE = kinetic energyJ = Joule m = masskg v = velocitym/sec

WARM-UP PROBLEM Determine the kinetic energy for a 250 g ball traveling at 2.5 km/min. (Remember to convert g to kg and km/min to m/s.)

Potential Energy (PE) Stored energy Gravitational Potential Energy –energy due to position PE = mghUnits PE = potential energyJ= Joule m = masskg g = force of gravity Earth = 9.8 m/sec 2 (CONSTANT) h = heightmeter

See sample problem #4 What is the minimum height the ball would need to be dropped from to achieve this velocity before impact with the ground?

Calorie (cal) [older unit] The amount of energy required to raise the temperature of 1 gram of water by 1 Celsius degree. Example #1: How much energy is required to raise 20 g of water from 50C to 60C? Convert this to Joules. {Remember 1 cal = J}

Law of Conservation of Energy Energy can neither be created nor destroyed in any chemical or physical process. It can be converted from one form to another.

Heat Sum total of all the KE of the particles in a sample. This can only be measured using indirect means when a change of heat occurs.

Temperature Measure of the average KE of the particles in a sample. Can be measured directly.

Properties of Matter Extensive Properties-properties that are dependent on the quantity of matter. (mass, volume, shape) Intensive Properties-Not dependent on the size of the sample, characteristic properties of that substance. (melting point, boiling point, density)

3 States of Matter [Actually 4 States] Solid-definite shape & volume, maintains shape without a container. Liquid-definite volume but indefinite shape, takes the shape of its container but does not fill. Gas-indefinite shape & volume, fills any container placed in. Plasma-highly ionized form of gas that exists at high temps. (surface of the sun)

Physical Characteristics Physical Properties-These are observed or tested without changing the substance. Physical change -These include changes of state such as melting, boiling, dissolving, grinding, filtering, etc.

Chemical Characteristics Chemical Properties-How a substance reacts with other substances. This is only observed in a chemical reaction. Chemical Change-When a substance is converted into a new substance. All properties and characteristics will change! Format: Reactants  Products (start) (yields) (ending)

Indicators of Chemical Change 1. Evolution of heat and/or light. 2. Production of a gas (not from boiling) 3. Production of a precipitate (ppt.) (solid but not from freezing) 4. Color change (be careful with this one, indicators cause color change but that is not chemical!)

WARM UP A runner burns about 10 kcal per minute. If the runner completes a race in one hour and fourteen minutes, how many kJ did he burn? How many J did he burn?

Mixtures Mixture-Physical combination of 2 or more substances. 2 Classifications:  Heterogeneous-different composition present [examples: sand, granite, milk of magnesia]  Homogeneous-same composition present throughout [examples: salt water, Gatorade, coffee]

Pure Substances Elements & Compounds  These always have the same properties  The same composition  They can not be separated without changing properties.

Element A substance that can not be broken down into another substance by chemical means. The smallest part is an atom There are approximately 90 naturally occurring elements.

Compound A substance that can be broken down into another substance by chemical means. The smallest part is a molecule or ion.