chapter 4: substances undergo a chemical change when they
TRANSCRIPT
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March 05, 2015
CHAPTER 4: Substances undergo a chemical change when they interact to produce different substances
A ____________ ____________ occurs when two or more substances combine to form new substances.
EXAMPLE: On the space shuttle, liquid hydrogen and liquid oxygen combine to form water. This reaction releases enough energy to put the shuttle in orbit around the earth.
WORD EQUATION:
Section 4.1 p 157 160
____________ : the starting materials in a reaction
____________: the new materials made in the reaction
A chemical reaction also occurs when a compound breaks down to form two or more new substances.
EXAMPLE: Car airbags are packed with an explosive chemical called azide, NaN3(s). When the vehicle is in an accident, sodium and large volumes of nitrogen gas are released. The nitrogen inflates the airbag instantly.
WORD EQUATION:
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March 05, 2015
PRACTICE:Write the word equations for the following reactions.
A. When hydrogen peroxide is poured onto a cut, it changes to water and oxygen gas.
B. Sodium and bromine react explosively to produce sodium bromide.
C. Carbon, water and sulfur dioxide are formed when sugar and sulfuric acid are mixed.
1. _______________: a chemical reaction that absorbs heat energy
'HEAT ENTERS' = ENDO
These reactions need a constant input of heat. When you touch them they often ______ ______ as heat is drawn from yourhand.
Some reactions absorb heat while others release heat.
chemical cold pack for first aid kids
cooking a steak (absorbs heat from the barbeque)
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March 05, 2015
2. ________________: a chemical reaction that releases heat energy
'HEAT EXITS' = EXO
These reactions produce heat.(Sometimes a little bit of heat may be needed to get the reaction started.)
burning a substance in the presence of O2
your body metabolizing food
Other Reactions Involving Oxygen:A.______________: when oxygen reacts with a substance
and gives off energyEX. burning wood:
wood + oxygen > carbon dioxide + water
B. ______________: when oxygen in the air reacts with a metal
EX: rusting: iron + oxygen > iron oxide
C. __________________________: when food for your cells reacts with oxygen to produce energy
Equation:glucose (food) + oxygen >carbon dioxide + water + NRG
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March 05, 2015
Questions 1. How are reactants different from products in a chemical reaction?
2. The following reaction occurs when you ignite chemical fire starter:2 CH3OH(l) + 3 O2(g)>2 CO2(g) + 4 H2O (g)A. What are the reactants? __________________________B. What are the products? __________________________
3. Compare: endothermic exothermic
4. Write the word equation:a. When magnesium burns in the presence of oxygen a bright
light is produced and white ashes called magnesium oxide is left over.
4. Compare combustion and corrosion using the Venn diagram below:
b. Water and oxygen gas are produced when hydrogen peroxide is put on a cut.
c. Zinc and hydrochloric acid are added together. A bubbling reaction occurs and hydrogen gas and zinc chloride are created.
Combustion Corrosion