1. No matter what reaction or change in properties occurs, the .

2. What conditions are necessary for the reactions in figure A to occur?

• The substances have to be mixed with water
• The substances have to sit for 40 minutes
• The substances have to be heated
• The substances have to be solid

3. Suppose 15 g of salt is dissolved into 100 g of water. What would the resulting mass of the mixture be?

• 100 g
• 115 g
• A little less than 100 g
• A little more than 100 g

4. Which of the following would be evidence of a chemical reaction occurring?

• no new substance is formed
• a state change, such as from liquid to gas
• a change in shape
• a temperature change

5. Your classmate thinks that not all substances release energy when they dissolve in water. Is there evidence from figure A to support this?

• Yes, hydrochloric acid increased in temperature drastically because it released and absorbed energy.
• Yes, salt caused the temperature to drop slightly because it absorbed energy instead of releasing it.
• No, all of the substances tested released energy over the time period that was tested.
• Partially, there might be substances that don’t release energy but none of the substances in figure A are evidence of this.

6. It’s most important that the reaction within this device heat energy to be into the coffee.

7. What are the criteria of the project?

• It needs to fit on the teacher’s desk and it needs to be safe enough to use in the classroom
• It needs to use chemical reactions
• It needs to stop your teacher from getting cranky
• It needs to warm up coffee using chemical reactions

8. What are the constraints of the project?

• It needs to warm up coffee using chemical reactions
• It needs to fit on the teacher’s desk and it needs to be safe enough to use in the classroom
• It needs to use chemical reactions
• It needs to stop your teacher from getting cranky

9. How could we measure the energy that’s been transferred to meet the criteria?

• Energy can be measured by looking at new substances that are formed, so we can measure how much of the reactants were changed into a new product.
• Energy can be measured by looking at the change in temperature in the coffee.
• Energy comes from matter changing and we could look at how much of the matter went through a chemical reaction.
• Energy can be measured by looking at the amount of fuel that’s consumed, so we can look at the change in weight after the chemical reaction.

10. Kami thinks that whatever substance releases the most energy when dissolved should be used in the design because it will keep the coffee warm the longest. What is the drawback of this logic?

• The substance releasing a lot of energy doesn’t relate to the temperature of the coffee increasing.
• Releasing a lot of energy would result in the reaction mixture eventually getting colder.
• If too much energy is released it could make the coffee too hot to drink.
• If too much energy is released the coffee would absorb less and not stay warm for very long.

11. Which of the following is a limitation that exists if calcium chloride is used in the designed solution?

• The substance should not be used near food or drinks because it is a chemical.
• The temperature it would keep the coffee at would be on the low end of the preferred temperature.
• The temperature change the substance causes happens slower than the other substances.
• The substance is not safe to use in the classroom.

12. How could one of the reactions in figure A be used in your design to solve your teacher’s problem?

• The substance could be added to a container that surrounds the coffee mug, as the coffee cools down the energy from the coffee will go into the substance and cause it to heat up.
• The substance could be mixed in with the coffee so that energy is released into the coffee when it dissolves in the coffee.
• The substance could be mixed with water in a container that surrounds the coffee mug so energy from the reaction goes into the mug.
• The substance could be mixed with water in a container that the coffee mug sits on top of, so the energy from the coffee goes into the reaction.

13. Which of the substances in figure A meet the criteria and constraints of the scenario best and why?

• Calcium chloride, because energy is released from the reaction and the substance is safe to handle and use near a drink.
• Salt, because the substance is commonly used in drinks and food so it is safe to handle and use.
• Any of the substances could be used because they would all cause the temperature of the coffee to increase.
• Hydrochloric acid, because the substance releases the most energy and will heat the coffee to the highest temperature.

14. Your teacher decides to try drinking more coffee throughout the day to help their grumpiness and asks you to modify your design to keep a larger volume of coffee warm. How could you test and modify the design to meet this new criteria?

• Change the type of material holding the reaction to see if less energy can be released from the reaction into the surroundings.
• Add more of the substance to water and see if it causes the temperature to be higher or stay warm longer.
• Increase the amount of water to see if there is a different type of reaction that occurs.
• Add additional layers between the reaction and the coffee mug to minimize energy from being transferred between the two.

15. Consider the reactions from the 3 substances in figure A. Describe the criteria that would allow for your teacher to use hydrochloric acid (dissolved in water) to keep their coffee hot enough. Be sure to also describe the constraints and include evidence from the models provided.

16. In the space below, draw a model of a device that uses a chemical reaction to keep your teacher’s coffee hot.

17. Explain how your solution works and how it uses a chemical reaction to keeps your teacher’s coffee hot.

18. What would be the best way to test how well a solution to this problem works?