Thermal Energy SG

The first glow sticks were patented by the US Navy in the 70's. They were called chemiluminescent signal devices. Today, glow sticks are still used by the military, emergency services, campers, divers and, of course, by kids for fun! The chemistry of a glow stick is pretty complicated. Sally's teacher let them experiment with glow sticks in science class. They bent the sticks, breaking the glass tube inside and the tubes began to glow bright colors."How can we make the glow sticks brighter", asked Maria? What is one suggestion you could give Maria to make the sticks glow even brighter?

• Take the glow sticks into a dark room.

• Put the glow stick in the freezer.

• Heat the glow stick in hot water.

• Wave the sticks around.

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NGSS.MS-PS1-4

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Juan Carlos and Michael are learning about chemical reactions and heat energy in science class. They have to design a device that releases heat and they decide to make some hand warmers. After some on-line research, they assemble the materials needed.There are only 4 things needed to make the handwarmer, all of them are very easy to aquire, if you dont already have them.

one large ziploc bag each one small ziploc bag each calcium chloride ice melter pellets water

The boys each made a hand warmer. They poured calcium chloride pellets into the bottom of larger ziplock bag. They filled the smaller bag about 1/4 full with water and then sealed the bag, pushing out as much air as possible. The smaller bag was placed into the larger bag and after squeezing out the air, the boys sealed their bags.When the bags were squeezed and the smaller bag opened releasing the water, the boys felt the larger bags get slightly warmer." How can we make the outer bag even warmer?" asked Juan Carlos. What would you tell the boys to try?

• Use more calcium chloride in the larger bag.

• Use less water in the smaller bag and more calcium chloride in the larger bag, making a more concentrated solution.

• Use larger bags and more reactants.

• Measure each reactant, experimenting to find the best ratio to produce the most heat.

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Jill is studying the temperature output of an ammonium chloride hand warmer with a calorimeter. What change should she expect to see in the temperature of the water over time?

• The water will remain a relatively constant temperature during the experiment.

• The water will continue to heat up as the experiment progresses.

• Initially the water will heat up and then it will slowly cool off as the hand warmer does.

• The water will gradually cool off throughout the experiment like the hand warmer.

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NGSS.MS-PS1-4

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When the power goes off, Jack does not have a flashlight so he uses a glow stick to provide light. He is not very satisfied with how long the glow stick lasts. Which idea is the most likely to improve the longevity of the glow stick?

• Increase the concentration both the main and activator phases.

• Enlarge the overall size and volume within the glow stick.

• Include a slow release activator phase to the main solution.

• Only increase the volume of the activator solution cell.

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NGSS.MS-PS1-1

During a science experiment students combine two substances in a beaker. The beaker becomes quite warm. What is the most likely reason the beaker changed temperature?

• The substances chemically reacted and released energy.

• The substances physically reacted and changed the beaker.

• The substances physically reacted and changed states of matter.

• The substances chemically reacted and absorbed energy.

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An equation for a chemical reaction is shown below.

2H₂(g)  +  O₂(g)  →  2H2O(l)  +  571.6kJ

Which of the following statements indicates that this reaction is exothermic?

• There are more reactants than products.

• Energy is released.

• A compound is formed.

• The reactants are two different gases.

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A 1-kg iron frying pan is placed on a stove. The pan increases from 20°C to 250°C. If the same amount of heat is added to a pan with a greater specific heat, what can you predict about the temperature of this second pan?

• The second pan would reach a lower temperature.

• The second pan would reach a higher temperature.

• No conclusion can be made from this information.

• The second pan would reach the same temperature.

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NGSS.MS-PS1-4

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A student is melting four different wax cubes in a laboratory investigation. The cubes range in size from 3g to 18g and are placed in a wax warmer with a constant heat of 45ºC. Which cube will take the least amount of time to melt?

• A wax cube with a mass of 12g

• A wax cube with a mass of 18g

• A wax cube with a mass of 5g

• A wax cube with a mass of 3g

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NGSS.MS-PS1-4

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Which of the following is not true of an ice cube being heated and starting to melt?

• The amount of thermal energy decreases.

• The temperature increases.

• The average speed of the molecules increases.

• The number of collisions between molecules increases.

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Two beakers were prepared with 150mL of water at two different temperatures, as shown above. Two identical ice cubes were added to each beaker of water. In which beaker would the ice cube melt the fastest?

• Beaker B because the water is cooler.

• Beaker A because the water is cooler.

• Beaker A because the water is warmer.

• Beaker B because the water is warmer.

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