Chemistry Wrap-Up

1. Chemistry Wrap-Up

2. Matter • Matter is anything that has mass and takes up space. • Atoms are the smallest unit of matter • Subatomic Particles: • Proton: positive • Neutron: neutral • Electron: negative • Nucleus: almost all mass, very dense, neutrons and protons, center of the atom

3. Matter • An element is the smallest unit that can be considered a pure form matter, single atoms are all of a specific element which is determined by number of protons • Two or more atoms can combine in specific ratios to form molecules

4. Elements and the Periodic Table • There are a finite number of elements • Elements on the periodic table are grouped according to similarities of their properties. • Elements in the same family share similar characteristics

6. Combining Atoms • The atoms of elements combine in ways that make up everything in the universe. • It’s like Lego: you can build many different things with only 200 different blocks by combining different amounts of blocks in different ways.

7. Compounds, Elements, Mixtures, and Solutions • Mixtures – two or more substances that are not chemically combined with each other and can be separated by physical means. The substances in a mixture retain their individual properties. • Solutions – a special kind of mixture where one substance dissolves in another.

8. Compounds, Elements, Mixtures, and Solutions cont. • Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means. • Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means.

9. To classify matter: • Is the matter uniform throughout? • Can it be separated by physical means? • Can it be separated by chemical means?

12. Molecular Motion • Atoms and molecules move depending on their amount of energy (heat) • When there is more energy, atoms are less attracted to each other and move faster • When there is less energy atoms are more attracted to each other and move slower

13. Phases of Matter • The movement of molecules causes matter to exist in three main phases: • Solid: lowest energy • Liquid: median • Gas: highest energy

14. Properties of Matter • All types of matter have specific properties that are unique to that type of matter and are independent of the size of the piece of matter

15. Density • A measure of how tightly packed the molecules are in a piece of matter • Density of 1g of gold is the SAME as the density of 100g of gold. • Density is independent of sample size • D=m/v

17. Other Examples • All of these properties values are regardless of HOW MUCH of a sample you have • Conductivity: how well a substance moves heat or electricity • Solubility: how well something dissolves in water • Magnetic properties: how magnetic something is

18. pH • pH (potential hydrogen) • A measurement of how acidic or basic a solution is • Measured on a scale from 0-14 • 0-6: Acids • 8-14: Bases • 7: Neutral

19. Chemical Reactions • Law of Conservation of Mass • Mass is conserved, the number of atoms reacting is the same as the number of atoms that make the product.

20. Physical v. Chemical Change • Chemical Changes • The chemical make-up of the substance is different. • Color change, fire, new smell, precipitate • Physical Changes • The substance is chemically the same • Crumpling paper, ice melting

21. Temperature and Chemical Change • A higher temperature will increase the speed of a reaction • A lower temperature will decrease the speed • This is because of the motion of the molecules