Changes in Matter. 2. Chemical Changes

Size: px

Start display at page:

Download "Changes in Matter. 2. Chemical Changes"

Sharon Logan
5 years ago
Views:

PSC 36 Changes in Matter There are three kinds of

the basic differences between these types of

physical, chemical, or nuclear changes. 1.

the substance is not changed Examples: crushing a

1 PSC 36 Changes in Matter There are three kinds of changes that matter can undergo: hanges C l a c i. Phys. Chemical Changes 1 3. Nuc lear C hange s Important for you: understand the basic differences between these types of changes also be able to identify examples as being physical, chemical, or nuclear changes. 1. Physical Changes = changes where the identity of the substance is not changed Examples: crushing a can dissolving sugar and water chopping wood shredding paper HO molecules Sugar molecule C1HO11

water (this is just gaseous water in the air

cool surface) The molecules are the same liquid HO

freezing into icicles as a solid, liquid, or gas.

gaseous HO boiling water Here's another interesting

.. solid CO gaseous CO Solid carb sublimat on dioxid

2 All phase changes are physical changes! Solid Liquid Gas gaseous HO liquid HO condensation of water (this is just gaseous water in the air condensing into liquid water because of touching a cool surface) The molecules are the same liquid HO regardless of whether they exist solid HO water freezing into icicles as a solid, liquid, or gas. They just move further apart as they go from solid to liquid, and liquid to gas. solid HO liquid HO liquid HO melting ice cubes gaseous HO boiling water Here's another interesting phase change: the sublimation of dry ice... solid CO gaseous CO Solid carb sublimat on dioxid e, CO es direc gaseous tly into carbon d ioxide! Terms for phase changes: "dry ice" is frozen CO (carbon dioxide). It is at C

3 . Chemical Changes = changes where new substances (new molecules) are produced. Examples: Formation of rusts (metal oxides): Products Reactants Fe + O ide Iron ox FeO3 iron metal + oxygen gas Fe + rust O O new molecules produced! Copper oxides new mole cules prod uced! Cu atoms react with O molecules to produce CuO molecules Burning (always involves oxygen gas reacting with something): Synonyms: Combustion = Burning Burning gasoline: new molecules produced! new molecules produced! Burning methane: Excess methane found in oil wells burned off.

4 3. Nuclear Changes = changes where new ELEMENTS (on periodic table) are produced. Fission: e.g.s: New Eleme nts Produced The sun produces its energy through fusion! Fusion: e.g.: the Sun fuses 60 million metric tons of hydrogen each second New Element Produced Alpha decay α-decay e.g. Beta decay β-decay e.g.

5 Classify each of the changes below as being physical (P), chemical (C), or nuclear (N): 1. Baking soda and vinegar react and bubbling results: NaHCO 3 + HC H 3 O NaC H 3 O + H O + CO. A magnet is used to pick up iron filings. 3. During photosynthesis a green plant uses carbon dioxide and water to produce glucose (a simple sugar). CO + H O C 6 H 1 O 6 + O. Carbon-1 isotopes are unstable and decay into Nitrogen Salt is dissolved in water. 6. A peeled apple turns brown. 7. An egg white turns from clear to white as it cooks. 8. Bronze is made by melting Copper and Tin, mixing them together, and then letting the mixture re-solidify. 9. Wood is burned: C + O CO 10. Heat is released when Uranium-38 changes into Thorium Napthalene, C H, is the main ingredient of mothballs. Napthalene 10 8 is a solid that sublimates to release the aromatic gas characteristic of mothballs. 1. A silver ring tarnishes over time. 13. The inside of your car windows fog-up on a rainy day. 1. Protein is digested by enzymes in the stomach. 15. Insects are sterilized using gamma rays, which are a biproduct as Cobalt-60 decays to Nickel-60.

6 For each item below, describe two changes that could be made to the item that would constitute physical changes, and two changes that would constitute chemical changes. physical changes chemical changes an apple a block of wax a glass of milk a cup of sugar a piece of paper A block of silver

7 Writing Equations for Alpha- and Beta- Decay Reactions Alpha Decay ( Rules: α decay) α 38 3 e.g. U Th + 1. ( an particle) is always produced. total mass on reactant side = total mass on product side 9 90 He Law of conservation of mass hold true since 3 + = 38. Total mass reactants = total mass reactants! 3. atomic number total reactant side = atomic number total product side Fill in the blanks: 6 1. Ra 88 + He Alpha- and beta-decay are also called transmutations. For example, U-38 "transmutes" into Th-3, and Pb-1 "transmutes" 6. Ra 88 + He into Bi Write the equation for the α decay of Po 10.. Write the equation for the α decay of Rn. Beta Decay ( β decay) Rules: β 1. ( a particle) is always produced _. mass reactant isotope = mass product isotope (since mass e = 0) 0 e _ 1 e.g. Pb 1 Bi 8 3. atomic number of product isotope is 1 more than that of reactant isotope Fill in the blanks: Bi Pa + e _ 0 0 e _ According to the law of conservation of mass, the mass of the product isotope must equal the mass of the reactant isotope (for beta decay). This is because, within the nucleus of the reactant isotope, a neutron converts into a proton and an electron. The electron (with negligible mass) is all that's lost. The proton has the same mass as the neutron, so the mass is unchanged e _ 0 3. Write the equation for the β decay of Pa 3.. Write the equation for the decay of Ac 7. β

8 1. Write the equation for the α decay of: a) Po 1 b) U 3 c) Th 8 d) Bi 1 e) Rn 0. Write the equation for the β decay of: a) Ra 8 b) Tl 08 c) Fr 3 d) Bi 1 e) Pb 1

9 3. Fill in the spaces in the following equations: a. Po Pb b. Sr Y + 38 c. Ra He + 1 d. 7N + 0 e 131 e. 53I + 0 e 6 f. 3Li + 0 e g. 88Ra + He. a) For alpha decay: Explain, according to the law of conservation of mass, why the mass number of the product isotope is less than the mass number of the reactant isotope. b) For beta decay: Explain, according to the law of conservation of mass, why the mass number of the product isotope is equal to the mass number of the reactant isotope.

2-1: Describing Matter. 8 th Grade Physical Sciences

2-1: Describing Matter. 8 th Grade Physical Sciences 8 th Grade Physical Sciences What is Matter? Matter is anything that has mass and takes up space. Properties of Matter Matter can be described in many ways; hard, soft, heavy, light, rough, smooth,