Chemistry
Matter is anything that has mass and takes up space. All matter is made of particles. The type and arrangement of the particles determines the properties of the matter. Most matter exists as solids, liquids, or gases.
Volume: the space an object takes up. Measured by: calculating L X W X H, or in ml with a Graduated Cylinder Mass: the quantity of matter contained in an object. Measured by: Triple-beam Balance or Electronic Balance Weight: the force produced by gravity acting on the mass of an object. Scientists express force in newtons, but they express mass in kilograms. Because gravity varies from place to place, weight can change but mass won t.
Physical Property= a characteristic of a substance that does not involve a chemical change. These include: density, color, what state of matter it typically exists in, hardness, melting point or boiling point Whether water is ice or liquid, it is still water. Changing its state doesn t change its identity. The sugar in the tea is still sugar, even if it is dissolved in the water of the tea.
Tearing paper into pieces is a physical change it is still paper. But, burning it changes its chemical composition. Burning paper turns it into a new substance. Chemical Properties= a property of matter that describes a substance s ability to participate in chemical reactions. Chemical properties can only be determined by trying to cause a chemical change! If it changes to something else, that was a chemical change.
The Formation of a Precipitate The Release or Absorption of Energy The Evolution of a Gas: the production of a gas is often observed by bubbling A Color Change in the Reaction System
In an equation, the substances on the lefthand side of the arrow are the reactants. The substances on the right side are the products.
All physical and chemical changes involve a change in energy. Energy is the ability to do work. Sometimes, energy must be supplied for the change to occur. Other times, energy is released. Both of these reactions involve Hydrogen and Oxygen Water!
Ice melting and water boiling are examples of physical changes. A physical change affects only the physical properties of a substance. When ice melts and turns into liquid water, you still have the same substance represented by the formula H2O. When water boils and turns into vapor, the vapor is still H2O. Only the physical state of the substance is changed. In contrast, the reaction of H and O to form H2O is a chemical change. http://www.nsf.gov/news/special_reports/che mistrynow/chem_ice.jsp
All matter is composed of about 110 different kinds of atoms. Atoms can be physically mixed or chemically combined to form all kinds of matter.
A pure substance is a sample of matter (either a single element or a single compound) that has definite chemical and physical properties. The helium atoms inside these balloons are an example of a pure substance. The copper wire inside these electrical cords is a pure substance.
Elements are pure substances that contain only one kind of atom. Copper and Helium are elements. Each element has its own unique set of physical and chemical properties and is represented by a distinct chemical symbol.
Some elements (such as Helium) exist as single atoms. Other elements exist as molecules: Molecule= the smallest unit of a substance that keeps all of the physical and chemical properties of that substance; it can consist of one atom or two or more atoms bonded together.
Pure substances that are not elements are called compounds. Compounds are composed of more than one kind of atom. Compounds are represented by formulas, which show the ratio of the atoms. The molecular formula and structural diagram of Aspirin:
A sample of matter that contains two or more pure substances is a mixture. Most kinds of food are mixtures (except for sugar and salt). Water is not a mixture of hydrogen and oxygen they are bonded as a molecule, not just physically mixed. Also, the ratio of two hydrogen to 1 oxygen is the same in every molecule.
A glass of sweetened lemonade is a mixture. If you have ever had a glass that is just too sweet or not sweet enough, you have experienced a characteristic of mixtures. A mixture doesn t always have the same balance of ingredients. Therefore, their properties can change.
Homogenous Mixtures describes a mixture that has a uniform distribution of materials throughout. Ex: sweetened tea or 14 karat gold Heterogeneous Mixtures is composed of components that are dissimilar (not alike, nor in equal quantities) Ex: Sand and water or a salad
Anything that has mass and takes up space All of the particles (atoms or molecules) in the sample are identical to each other Molecule: A particle made of two or more atoms bonded together Contains two or more different types of particles (atoms or molecules) not bonded to each other Pure substances made of only one type of atom Pure substance made of more than one type of atom bonded together Mixture made of different types of particles that is uniformly distributed throughout. Mixture that is made of different types of particles that do not have equal quantities
Your friend mentions that she eats only natural foods because she wants her food to be free of chemicals. What is wrong with this reasoning? Is toasting bread an example of a physical or chemical change? Why? Classify each of the following as a physical change or a chemical change and provide evidence: a. cracking an egg b. using bleach to remove a stain from a shirt c. burning a candle d. melting butter in the sun