NJ ASK REVIEW Physical Science

1. NJ ASK REVIEWPhysical Science 8th grade science

2. matter • Matter – anything that has mass and takes up space • Some types of matter are called • Substance – • Every form of matter contains both properties. substances A single kind of matter that is pure. *substances have the same type of make up and properties no matter where it comes from – Examples: Salt, sugar and water physical and chemical

3. Physical properties • A characteristic of a pure substance that can be observed without changing it to another substance. • Physical properties can be observed by • Examples of physical properties: touching or looking at a substance. • Melting/freezing point • Hardness • Texture • Color

4. Chemical properties • A characteristic of a pure substance that describes its ability to change into different substances. • Chemical properties can only be observed when • Examples: a substance combines with something else and forms a new substance. • Flammability • Rusting

5. Chemistry is all about how matter changes! • Physical Change - any change in the form or appearance of matter. • A physical change change the substances • Examples: DOES NOT chemical makeup • Crushing • Ripping • Breaking • Chopping • Blending • Dissolving

6. Chemistry is all about how matter changes! • Chemical change - When one substance changes into one or more different substances • Atoms are rearranged not taken away or added! • Example: • Keep in mind… during a chemical or physical change we call this • Oxidation: rusting (this occurs when iron and oxygen mix) matter cannot be created or destroyed the law of conservation of mass

7. Understanding chemical reactions • We know that a chemical change occurs when • We can also call this a • Chemical Reaction - one or more substances change into a new substance. chemical reaction A process in which atoms of one or more substances rearrange to form one or more new substances.

8. Signs of a chemical reaction

9. How can we describe a chemical reaction? • By using • Chemical equation - a description of a reaction using element symbols and chemical formulas. a chemical equation

10. PARTS OF A CHEMICAL EQUATION • Reactant – • Yield (or produces) – • Product – • Subscript – the starting substances in a chemical reaction (belong to the left of the arrow) the arrow used to represent the chemical reaction taking place. the substances produced by the chemical reaction (belong to the right of the arrow) Describes the number of elements in a compound. Belongs after the atom it represents and is written small. **If there is no subscript it means there is only one atom of that element**

11. Label all parts of the following chemical equation

12. Chemical bonds contain energy • Chemical bonds contain • Some chemical reactions more energy than they absorb. • Some chemical reactions more energy than they release. chemical energy release absorb

13. Endothermic vs. exothermic reactions • Endothermic Reaction – • Exothermic Reaction - chemical reactions that absorb thermal energy. chemical reaction that releases thermal energy.

14. After talking about atoms that are chemically combined… • Chemical bonds • Covalent bonds – A chemical bond formed when two atoms share electrons.

15. Atoms transfer (give or take) valence electrons to reach stability • Ionic bonds -

16. Heterogeneous mixture • A mixture in which substances are not evenly mixed. • Examples: • Salad • Granite • Soil

17. Homogeneous mixture • A mixture in which two or more substances are evenly mixed on the atomic level but NOT bonded together. • Examples: • Another name for “homogeneous mixture” is • Air • Soda solution

19. Mixtures can be separated • Mixtures can be separated because • Mixtures can be separated by using physical methods including: • Filtering • Boiling • Magnetism they are not bonded together separation by size separation by boiling point separation by magnetism (for objects attracted to magnets)

20. Substance vs. mixture

21. Acids and bases… necessities to our everyday life! • The pH scale is used to measure how and a substance is. • The pH scale is a range of values from to . ACIDIC BASIC 0 14

22. pH SCALE NEUTRAL • Something that is neither acidic or basic is • Neutral is the pH of: • Any value below the pH of 7 is: • Any value above the pH of 7 is: **Label the pH scale on your paper** 7 (water) ACIDIC BASIC

23. acids • Chemicals in which the positive ion is a hydrogen atom • Ion – an atom or group of atoms that has a positive or negative charge • Properties • Tastes sour • Reacts with metals • Turns litmus paper red • Reacts with carbonates – (causes bubbles to appear) • Corrosive – (eats away other materials) **Litmus is a colored chemical which can change from red to blue and back again – the color it changes depends on whether the substance is basic or acidic.

24. bases • Substances with a negative ion called Hydroxide • Properties: • Tastes bitter • Turns litmus paper blue • Slippery

25. FROM EXPERIENCE NAME SOME ACIDS AND BASES: ACIDSBASES pH = 8-9 pH = O NEUTRAL pH = 10 pH = 2 pH = 12 pH = 3 pH = 14 pH = 4

26. pH SCALE • The pH scale expresses the concentration of ions in a solution. • Low pH tells you: • High pH tells you: HYDROGEN THERE IS A HIGH CONCETNRATION OF HYDROGEN IONS. THERE IS A LOW CONCETNRATION OF HYDROGEN IONS.

27. BEING SAFE • In order to handle acids and bases safely you need to know their and • Concentration – • A reaction between an acid and a base is called: • Neutralization - pH CONCENTRATION The amount of one material in certain volume of another material. NEUTRALIZATION A reaction of an acid with a base creating a solution that is no longer as acidic or basic as the original solution.