Describing Matter and Changes in Matter

1. Describing Matter and Changes in Matter Matter does “matter”!

2. What is matter? • Matter is anything that has mass and takes up space. • The “stuff” around us is made of matter, and we are made of matter also. • Examples: air, plastic, metal, glass, paper, water, cloth, etc.!

3. Properties of matter • Substance: a single kind of matter that is pure, meaning it was the same makeup, or composition, or specific set of properties. • Every form of matter has two kinds of properties: • Physical properties • Chemical properties

4. Physical properties of matter • A physical property is a characteristic of a pure substance that can be observed without changing it into another substance. • A physical property of water is that it freezes at 0 C degrees (32 degree F) • Other physical properties of matter are density, hardness, texture, shine, flexibility, and color.

5. Chemical properties of Matter • A chemical property is a characteristic of a pure substance that describes its ability to change into a different substance. • To observe the chemical properties of a substance, you must change it into another substance. • Chemical properties are used to classify substances. • An example would be a category of gases which are combustible vs. a category of gases which are not combustible

6. Elements • Ancient Greeks believed that matter and all of the “stuff” in the world is comprised of four elements Earth, Fire, Water, and Air. • An element is a pure substance that can not be broken down by chemical or physical means. • Elements are the simplest of substances. • The elements are found on the periodic table of elements.

8. Particles of Elements • Atoms are the particles of elements • An atom is the basic particle from which elements are made. • Atoms are made of even smaller particles: • A nucleus which is positively charged and it is surrounded by a cloud of electrons (which have a negative charge).

9. Atoms

10. Chemical bonds • When atoms combine they form chemical bonds which is a force of attraction between two or more atoms. • In many cases, atoms combine to form larger particles called molecules. • Molecules are groups of two or more atoms held together by chemical bonds. • Examples: water, oxygen, and carbon dioxide. Water Molecule (H2O) Oxygen Molecule (O2)

11. “Describing Matter” to be continued… • Homework: “What is Matter” worksheet

12. Calcium Carbonate (Compound) (Shell of a snail) Calcium (element) Carbon (element) Oxygen (element) Compounds • Compounds are pure substances made of two or more elements chemically combined into a fixed ratio. • A compound may be represented by a chemical abbreviation. • When two or more elements are placed together the result is a compound which has different characteristics than either of the original elements. CaCO3

13. Mixtures • Mixtures are substances held together by physical forces, not chemical. They can be separated physically. • Solutions are also mixtures. • Mixtures differ from compounds in two ways: 1) each substance in a mixture keeps its individual properties. 2) the parts of a mixture are not combined in a fixed ratio. Examples: oil and water, salt water, concrete

14. Heterogeneous Mixtures • A heterogeneous mixture is when two or more substances are mixed but do not combine chemically to form a single substance. • Examples: salad, oil and water, rocks, chocolate chip cookie, chicken soup, etc. • We can separate all the components of the salad to the left, so it is a heterogeneous mixture.

15. Homogenous Mixture • A homogeneous mixture is what you have when you mix two or more substances together so that the composition is the same throughout the mixture. • Examples: sugar and water, brass (mixture of copper and zinc), air that we breathe (oxygen and nitrogen gases), soft drinks, milk, etc. • A solution is an example of an homogeneous mixture.

16. The two types of changes in matter • Physical changes: any change that alters the form or appearance of the matter, but does not alter the properties of the matter. • A substance that undergoes a physical change is still the same substance after the change. • Example: water exists as a solid, liquid, or a gas. • Chemical changes: any change which results in the production of one or more new substances is a chemical change. • The properties of the new substances are different than the properties of the original substances. • Example: Hydrogen peroxide turns into water and oxygen gas when it is used.

17. Examples of Chemical Change

18. Law of the conservation of matter • Simply stated that when matter changes either chemically or physically, that matter is not created nor destroyed, it has just changed to another form or forms. • Example: CH4 (methane) + 2O2 (oxygen) = CO2 (carbon dioxide) + 2H2O (water) Notice how the number of atoms did not change after the combustion.

19. Matter is neither created nor destroyed: • Before the reaction CH4(methane) + 2O2(oxygen) • The total number of atoms before the reaction is: • 1 Carbon (C) • 4 Hydrogen (H) • 4 Oxygen (O) • After the reaction CO2(carbon dioxide) + 2H2O (water) • The total number of atoms after the reaction is: • 1 Carbon (C) • 4 Hydrogen (H) • 4 Oxygen (O)

20. Homework: “Molecules and Compounds” worksheet