The Science of Chemistry Chapter 1 The Science of Chemistry

SCIENCE Latin having knowledge Study concerned with the observation and classification of facts examples:

SCIENTIST Search for relationships that can be used to explain and predict the behavior of things HOW??? EXPERIMENT

CHEMISTRY A Laboratory science that deals with the composition, structure and properties substances and the changes they undergo

Section 1-1 What is Chemistry? Objectives: Describe the characteristics of the three most common physical states Draw models to represent solids, liquids & gases Write a word equation for a chemical reaction Identify the reactants and products in a chemical reaction Distinguish between exothermic and endothermic reactions

Describe the characteristics of the three most common physical states A… States of Matter B… Kinetic Molecular Theory

Physical States solid liquid gas fixed volume and shape fixed volume Sodium Mercury Silicon Nitrogen Neon solid fixed volume and shape liquid fixed volume shape of container, horizontal top surface gas takes shape and volume of container

The Big Three: Water S,L,G Solid Liquid Gas

B. Kinetic Molecular Theory KMT Particles of matter are always in motion. The kinetic energy (speed) of these particles increases as temperature increases.

B. Four States of Matter Solids very low KE - particles vibrate but can’t move around fixed shape fixed volume

B. Four States of Matter Liquids low KE - particles can move around but are still close together variable shape fixed volume

B. Four States of Matter Gases high KE - particles can separate and move throughout container variable shape variable volume

B. Four States of Matter Plasma very high KE - particles collide with enough energy to break into charged particles (+/-) gas-like, variable shape & volume stars, fluorescent light bulbs, CRTs

The Big Three States of matter demo

The Big Three #8 States of Matter Gas Liquid Solid

3 States of Bromine Solid Bromine Liquid Vapor

Draw models to represent solids, liquids & gases

Solid

Kinetic Molecular Theory: Solid particles are tightly packed together in regular array particles vibrate about average positions seldom squeeze past other atoms results in a rigid material with a small, fixed volume for a given mass external shape often reflects internal arrangement of particles

Liquid

Kinetic Molecular Theory: Liquid particles are arranged more randomly than in solid particles less confined so that they can move past one another particles are a little further apart, thus slightly larger, fixed volume particles are constantly interacting with one another

Gas

Kinetic Molecular Theory: Gases particles in continuous, random, rapid motion collisions between particles are elastic volume occupied by the particles is negligibly small effect on their behavior attractive forces between particles have a negligible effect on their behavior gases have no fixed volume or shape, take the volume and shape of the container

Write a word equation for a chemical reaction Write a word equation for a chemical reaction. Identify the reactants and products in a chemical reaction

Chemical Reactions: A chemical reaction occurs when two or more chemical substances are mixed together. This means that the atoms that were joined together in the original substances break apart and rearrange themselves to make a new substance, one or more substances may be transformed into one or more new substances. This new substance is quite different from the original substances.

Chemical Reactions: Reactant + Reactant ----> Product Some products of chemical reactions are heat, light, sound and changes in color.

Chemical Reactions: Examples of Chemical Reactions: A sparkler contains magnesium. This, when lit, reacts with oxygen in the air and produces light and heat.  2Mg + O2  2MgO + Energy Reactants Products Yields

Chemical Reactions: Examples of Chemical Reactions: The chemicals inside a rocket, when lit, react with the oxygen in the air and produce heat, light and sound. 2H2 + O2 2H2O

Distinguish between exothermic and endothermic reactions When chemical reactions occur, as well as the formation of the products, there is also a heat energy change which can often be detected as a temperature change. This means the products have a different energy content than the original reactants (see the reaction profile diagrams below).

Distinguish between exothermic and endothermic reactions

Distinguish between exothermic and endothermic reactions If the products contain less energy than the reactants, heat is released or  given out to the surroundings and the change is called exothermic. The temperature of the system will be observed to rise in an exothermic change. Examples: the burning or combustion of hydrocarbon fuels the burning of magnesium, reaction of magnesium with acids, or the reaction of sodium with water the neutralization of acids and alkalis Thermite reaction

Distinguish between exothermic and endothermic reactions If the products contain more energy than the reactants, heat is taken in or absorbed from the surroundings and the change is called endothermic. If the change can take place spontaneously, the temperature of the reacting system will fall but, as is more likely, the reactants must be heated to speed up the reaction and provide the absorbed heat. Examples: the thermal decomposition of limestone