Chemistry - investigates and explains: structure and properties/behavior of matter Matter = anything that takes up space and has mass = everything around you Matter is made up of atoms Mass = amount of matter that an object contains What is Matter?

properties = characteristics and behavior of matter (includes changes that matter undergoes). What color is it? Is it solid, liquid or gas Is it reactive? structure = composition what matter is made of how matter is organized. How do we classify matter?

So how do figure out what matter is made of? Macroscopic View = large enough to be seen okay for general properties like color, state, conductivity, etc. Submicroscopic View - too small to be seen by even a microscope good for finding out true structure

To visualize the submicroscopic view we create models ***Differencences in behavior are due to different arrangement of atoms sucrose and aspirin are both composed of carbon, hydrogen, and oxygen aspirinsucrose

Classifying matter What is it made of? qualitative observation is one that can be made without measurement describes color, odor, shape, or some other physical characteristic that relates to the five senses

how much of each of the elements is present? A quantitative observation is one that uses measurement = numerical data. Classifying matter

Examples of the physical properties of a chunk of matter include its: solubility, - dissolves in water? melting point, boiling point, color, density, electrical conductivity, and physical state (solid, liquid, or gas).

A physical change is a change in matter that does not involve a change in the chemical identity of individual substances. Examples of physical changes include: boiling, freezing, melting, evaporating, dissolving, and crystallizing.

Classify by purity Is it a pure substance or mixture? Pure substance = sample of matter, either a single element or a single compound that has definite chemical and physical properties Classifying Matter

substance is not changed = no fixed composition the basic identity of each Mixture = made up of different kinds of matter Pure Substance or Mixture?

heterogeneous mixture is one with different compositions, depending upon where you look Pure Substance or Mixture?

Homogeneous mixtures are the same throughout. Another name for a homogeneous mixture is solution. Pure substance or a mixture?

When you dissolve sugar in water, sugar is the solute—the substance being dissolved. The substance that dissolves the solute, in this case water, is the solvent. When the solvent is water, the solution is called an aqueous solution. Pure substance or a mixture?

Alloys are solid solutions that contain different metals and sometimes nonmetallic substances. Pure substance or a mixture?

compound = pure substance that can be broken down into simpler substances. element = substance that cannot be broken down into simpler substances. Element or Compound? salt gold

compound is a chemical combination of two or more different elements joined together in a fixed proportion with a unique set of chemical and physical properties Compounds

Compounds Are More Than One Element The properties of the compound are different from the properties of the elements that compose the compound. silver + bromine = silver bromide

Compounds Are More Than One Element A formula is a combination of the chemical symbols that show what elements make up a compound and the number of atoms of each element. CompoundFormula CaffeineC 8 H 10 N 4 O 2

States of Matter Most matter on Earth exists in one of three physical states: solid, liquid, or gas. A fourth state of matter, called plasma, is less familiar. Changes in state are examples of physical changes because there is no change in the chemical composition identity of the substance. Ice can melt back to form liquid water, and steam will condense on a cool surface to form liquid water.

States of Matter Some substances are described as volatile, which means that they change to a gas easily at room temperature. Alcohol and gasoline are more volatile than water.

Density is the amount of matter (mass) contained in a unit of volume. Density is measured in units of grams (mass) per milliliter (volume) or g/mL Density

Styrofoam has a low density or small mass per unit of volume. Stones have a large density or a large mass per unit of volume Density

Chemical Properties Chemical properties are those that can be observed only when there is a change in the composition of the substance. Rusting is a chemical reaction in which iron combines with oxygen to form a new substance, iron oxide. Inability to react is also a chemical property.

PhysicalChemical densityReactivity / stability Melting/freezing point colorFlamablility conductivity solubility Physical vs. chemical properties Physical change = NO change in composition Chemical change = change in chemical composition

Below are listed changes that can be observed in everyday life. Tell whether it is a physical change or a chemical change. Then explain the basis on which you made your decision. 1.an icicle melting 2.charcoal burning 3.magnetizing a piece of steel 4.iron rusting 5.rubbing alcohol evaporating from the skin

Chemical Changes chemical change, the change of one or more substances into other substances. A chemical property always relates to a Another term for chemical change is chemical reaction.

chemical change involves only a rearrangement of the atoms. Atoms do not just appear or disappear. ******Law of Conservation of Mass****** In a chemical change, matter is neither created nor destroyed. aka: the law of conservation of matter. Chemical Reactions

Chemical Reactions and Energy All chemical changes also involve some sort of energy change. Energy is either taken in or given off as the chemical change takes place. Energy is the capacity to do work. Work is done whenever something is moved.

Chemical Reactions and Energy Energy is also produced and released in the form of heat and light. Chemical reactions that give off heat energy are called exothermic reactions.

Chemical reactions that absorb heat energy are called endothermic reactions. Chemical Reactions and Energy

Identify each of the following as either a compound or a mixture. A. sand B. water C. juice

Answers A. sand B. water C. juice mixture compound mixture

Classify each of the following as a chemical or physical property. A. density B. reactivity C. color D. melting point

Answers A. density B. reactivity C. color D. melting point physical property chemical property physical property

Scientific Method – answer a question or study a situation A typical scientific method includes: making observations, forming a hypothesis, performing an experiment, and arriving at a conclusion.

A hypothesis is a possible explanation for what has been observed An experiment is a set of controlled observations that test a hypothesis Scientific Method

Scientific Methods The variable that is changed in an experiment is called the independent variable. The variable that you watch to see how it changes as a result of your changes to the independent variable is called the dependent variable.

Scientific Methods Many experiments also include a control, which is a standard for comparison. A conclusion is a judgment based on the data obtained in the experiment.

A student tests the ability of a given chemical to dissolve in water at three different temperatures. independent variable: temperature; dependent variable: ability to dissolve in water Answer 1a Question 1a

A farmer compares how his crops grow with and without phosphorous fertilizers. independent variable: presence of phosphorous fertilizer; dependent variable: crop growth Answer 1b Question 1b

a.alloyh.law of conservation of mass b.aqueous solutionsi.mass c.chemical propertyj.matter d.compoundk.physical change e.energyl.properties f.exothermicm.quantitative g.formulan.solute Matching Match each item with the correct statement below. ____29.The type of change in which the identity of substances does not change. ____30.A chemical combination of two or more elements joined together in a fixed proportion. ____31.The fact that matter can be neither created nor destroyed in a chemical change. ____32.Solutions in which water is the solvent. ____33.The behavior of matter and its characteristics. ____34.A solid solution usually consisting of two or more metals. ____35.Any chemical reaction that gives off energy. ____36.The combination of chemical symbols that describes the composition of a chemical compound. ____37.The measure of the amount of matter that an object contains. ____38.An observation that makes use of measurement. ____39.Can be observed only when there is a change in composition of a substance. ____40.Anything that takes up space and has mass. ____41.The material that is dissolved in a solution. ____42.The capacity to do work.