Temperature and heat

Carla's bath is full of water at $38\ ^\circ\text{C}$ and on the kitchen table there is a cup of coffee at $70\ ^\circ\text{C}$. The scene is shown in the figure.

1. a) Which is at a higher temperature, the bathwater or the coffee?
2. b) Which of the two stores more thermal energy?
3. c) Explain in your own words the difference between temperature and heat.

The weather app on Izan's phone says that it is $14\ ^\circ\text{C}$ outside right now.

1. a) What quantity does a thermometer measure?
2. b) In which unit is temperature measured in Spain?

State whether the statement is true or false and correct the idea: "Heat and temperature are two names for the same thing."

Aitana puts a cold spoon into her bowl of very hot soup. Observe the figure.

1. a) Which object gives off heat and which receives it?
2. b) What happens to the temperatures of the soup and the spoon after a while?

Nadia drops an ice cube into a glass of soft drink that is at room temperature. Observe the figure.

1. a) Which body loses heat and which gains it?
2. b) How can this heat exchange be observed?

On a summer afternoon, the pool water is at $24\ ^\circ\text{C}$ and the air is at $31\ ^\circ\text{C}$.

1. a) Who transfers heat to whom, the air to the water or the water to the air?
2. b) Which of the two will change temperature more slowly? Why?
3. c) If this situation lasted a very long time, what maximum temperature could the water reach?

To bathe his little brother, Álex mixes a saucepan of cold water with a saucepan of hot water. Is the mixture hotter than the hot water, colder than the cold water, or at an intermediate temperature? Explain your answer.

In the kitchen you mix half a litre of water at $20\ ^\circ\text{C}$ with another half litre of water at $60\ ^\circ\text{C}$. Since there is the same amount of each, the final temperature is right in the middle. The diagram summarises the mixture.

1. a) Calculate the final temperature of the mixture.
2. b) Explain why it is neither $20\ ^\circ\text{C}$ nor $60\ ^\circ\text{C}$.

Julia prepares warm water by mixing two glasses of cold water at $10\ ^\circ\text{C}$ with one glass of hot water at $70\ ^\circ\text{C}$. The diagram summarises the mixture.

1. a) Without calculating, will the final temperature be closer to $10\ ^\circ\text{C}$ or to $70\ ^\circ\text{C}$? Why?
2. b) When the amounts are not equal, the final temperature is a weighted average that takes into account how much of each water there is. Check it: add $2 \cdot 10 + 70$ and divide the result by $3$.
3. c) What are we assuming about the heat lost to the glass or to the air?

In the fireplace, an ember remains at $700\ ^\circ\text{C}$ and on the wall there is a radiator at $60\ ^\circ\text{C}$. However, the radiator heats the entire room, while the ember barely heats its immediate surroundings.

1. a) Which of the two is at a higher temperature?
2. b) Explain why the radiator heats more, considering its size.

A documentary shows a giant iceberg at $0\ ^\circ\text{C}$ and, at home, a steaming cup of tea at $90\ ^\circ\text{C}$.

1. a) Which of the two has a higher temperature?
2. b) Which stores more thermal energy?
3. c) What needs to be known, besides temperature, to compare the energies of two objects? Use this example to explain the difference between heat and temperature.

The heated towel rail in the bathroom is at $50\ ^\circ\text{C}$ and heats the whole bathroom; the flame of a match is at around $400\ ^\circ\text{C}$ and barely heats anything.

1. a) Which of the two has a higher temperature?
2. b) Which transfers more energy to its surroundings?
3. c) What two things must be taken into account to know how much heat an object can release?