1. When you hold a piece of chocolate in your hand, why does the
chocolate melt?
2. Which is a larger unit of heat: calorie, kilocalorie, Btu, or joule?
KiloCalorie
Btu
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1. When you hold a piece of chocolate in your hand, it melts due to the process of heat transfer. Heat is transferred from your hand to the chocolate, causing its temperature to increase. As a result, the chocolate's particles gain more energy, causing them to move faster and loosen their arrangement. This causes the solid chocolate to turn into a liquid state, which we commonly refer to as melting.
To understand this process in more detail, you can study the concept of heat transfer. Heat transfer occurs through three methods: conduction, convection, and radiation. In the case of holding chocolate, conduction is the primary method of heat transfer. Conduction involves the direct transfer of heat energy between objects that are in physical contact. In this case, heat from your hand is conducted to the chocolate, causing it to melt.
2. The largest unit of heat among the options provided is the kilocalorie (kcal).
Here's how the units of heat compare to each other:
- Calorie (cal): The calorie is the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius. It is a smaller unit of heat.
- Kilocalorie (kcal): The kilocalorie is equivalent to 1,000 calories and is commonly used to measure food energy.
- British Thermal Unit (Btu): The British Thermal Unit is a unit of heat commonly used in the United States. One Btu is approximately equal to the amount of heat energy needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit.
- Joule (J): The joule is the SI unit of energy and heat. It is a smaller unit compared to the kilocalorie and Btu. One calorie is equivalent to approximately 4.184 joules.
To determine which unit is larger, we can compare their numerical values. Using the conversion factors, we find that 1 kilocalorie is equal to 1,000 calories, 1 calorie is approximately 0.00397 Btu, and 1 calorie is approximately 4.184 joules. Therefore, the kilocalorie is larger than the calorie, Btu, and joule.