CHEMISTRY 8

Which model of a chemical reaction illustrates the law of the conservation of mass?

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Two clear liquids are mixed together in a beaker.What evidence suggests that a chemical reaction occurred?

• The mixture remained clear

• The liquids separated

• The mixture became warm

• The liquids became uniform

A fry pan being heated by a hot stove is a good model of ​ (a)  

• conduction
• convection

A fry pan being heated is a good model of conduction because thermal energy is being transferred ​ (a)  

• between objects in direct contact
• by electrical energy
• from a hot object to a cool one

A design for a hand warmer is shown below. When the metal disk is bent, the dissolved chemicals begin crystallizing around the disk and spread throughout the container. As the chemicals crystallize, they release heat. However, the container gets so hot that it is uncomfortable against skin. Which design modification would best address this problem?

• using a larger metal disk

• making the plastic container more rigid

• wrapping an insulator around the container

• replacing the metal disk with a plastic disk

WHICH OF THE FOLLOWING ARE EXAMPLES OF CONDUCTION?​ ​ (a)  

• a person's skin getting warm in hot shower
• steam rising from a teapot
• a microwave oven causing water to boil

Which are examples of convection?​ (a)   ​ ​ (b)  

• steam rising from a teapot
• hot magma moving from Earth's core to ground
• a person's skin getting warm in shower
• a microwave oven causing water to boil

Which is an example of radiation?​ (a)  

• a microwave oven causing water to boil
• a person's skin getting warm from shower
• steam rising from a teapot

Food becoming hot in the pan is a good model for ​ ​ (a)  

• conduction
• convection

food becoming hot in the pan is an example of conduction because thermal energy is being transferred by ​ (a)  

• direct contact
• by the movement of fluids
• by a device that uses electricity