First, heat is a form of energy, so it can be counted and measured. Energy has many forms, but it doesn’t appear or disappear. No magic. It can be measured in calories — the heat that raises one gram of water 1°C. That’s a tiny amount, so it’s common to use capital letters — Calories (Cal) or Kalories (Kal or Kcal) to represent 1000 small calories. If you use joules: 4.2 joules = 1 calorie.
The numbers have been known for a long time, but they are sometimes ignored or avoided where counting is unwelcome. Same for people who don’t want to count food calories, which is unscientific but permits other pleasures of eating, such as taste and the “freedom” to follow impulse and image, such as, “If it’s green, it’s good for you.”
We scientists can enjoy food, too, even if we count calories: 9 Kcal/gram of fats or oils and 4 Kcal/gram of proteins and carbohydrates (starch, sugars), if digested and available. Yes, fats are nutrients as energy sources, and proteins are the same as starches and sugars, but public image says otherwise. Water — 80% for meat and variable in veggies — is also good for you but not a source of energy. So, it doesn’t count. The internet and food labels are full of this info, but remember it’s per gram, so how much you eat matters. Around 30 grams = an ounce and 454 grams = 1 pound, so don’t let the grams stop you.
The second item to get clear is temperature scales. We need to speak both C and F, and if we have a gauge or data point, know what the units are. It’s easy: 5°C = 9°F and 0°C is 32°F (water freezes to ice, same molecules but organized structure). Fahrenheit (F) invented the thermometer in 1717, but Celsius (C) based the scale on water freezing and boiling in seaside Sweden, same as in sea level USA (it varies with altitude, but he didn’t know that).