Food energy requirements

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Energy in Food

Food is a store of **chemical energy** that is transferred to us when we eat.
The unit of energy for food is the **kilojoule (kJ)**; 1 calorie = 4.2 J.
A balanced diet provides the right amount of energy and nutrients.

Consequences of Imbalance

Eating **too little** leads to weight loss, starvation, and eventually death.
Eating **too much** leads to weight gain, **obesity**, heart disease, and diabetes.
Malnutrition results from an unbalanced diet.

Metabolic Rate

**Basal metabolic rate (BMR)** is the energy needed to survive when inactive.
**Physical activity level** adds to BMR to give the overall metabolic rate.
Factors affecting metabolic rate: **age**, **gender**, **body mass**, **exercise**, **pregnancy**.

Daily Energy Requirements

Average man needs **10 500 kJ** per day; average woman needs **8400 kJ** per day.
Active people need more energy than inactive ones.

Food Labels

Food labels show energy content and amounts of food groups (carbohydrates, fat, fibre, protein).
Labels help consumers choose a balanced diet.

Factors affecting overall metabolic rate and the role of food labels.

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Practice questions

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1.Which unit is used when referring to the energy content of food?
Easy
- AKilojoule (kJ)
- BJoule (J)
- CCalorie
- DKilocalorie
2.What is the term for having too much body fat?
Easy
- AMalnourishment
- BObesity
- CStarvation
- DDiabetes
3.Which two components make up a person's overall metabolic rate?
Medium
- ABasal metabolic rate and physical activity level
- BAge and gender
- CBody mass and exercise levels
- DEnergy intake and energy expenditure
4.According to the source, which of the following is a risk of obesity?
Medium
- AHeart disease
- BStarvation
- CMalnourishment
- DWeight loss
5.A man requires 10 500 kJ per day and a woman requires 8 400 kJ per day. What is the ratio of the man's requirement to the woman's requirement?
Hard
- A5:4
- B4:5
- C5:3
- D3:5
6.Why is it important that food labels show the amount of each food group?
Medium
- ATo help people choose a balanced diet
- BTo increase the price of food
- CTo make food look more attractive
- DTo reduce the energy content
7.What is the basal metabolic rate a measure of?
Easy
- AEnergy needed when inactive
- BEnergy needed for exercise
- CTotal energy used per day
- DEnergy stored in food
8.Which factor does NOT affect overall metabolic rate according to the source?
Medium
- AHeight
- BAge
- CGender
- DPregnancy

More questions

9.If someone eats too little food for a long time, what condition may eventually lead to death?
Hard
- AStarvation
- BObesity
- CDiabetes
- DHeart disease
10.One calorie is equal to how many joules?
Easy
- A4.2 J
- B42 J
- C0.42 J
- D420 J
11.Which statement about energy requirements is correct?
Medium
- AMen generally require more energy than women.
- BWomen generally require more energy than men.
- CChildren require more energy than adults.
- DPregnant women require less energy.
12.A person's overall metabolic rate increases with which of the following?
Hard
- AIncreased exercise
- BIncreased age
- CDecreased body mass
- DPregnancy (decrease)
13.Which of the following is the unit of energy used when referring to food?
Easy
- Akilojoule (kJ)
- Bjoule (J)
- Ccalorie
- Dwatt (W)
14.A person's overall metabolic rate is the sum of which two components?
Medium
- Abasal metabolic rate and physical activity level
- Bage and gender
- Cbody mass and exercise level
- Denergy intake and energy expenditure
15.A student wants to investigate the energy content of a food sample. They burn the food under a test tube containing a known volume of water and measure the temperature rise. Which piece of equipment is essential for this experiment?
Medium
- AA thermometer
- BA balance
- CA stopwatch
- DA measuring cylinder
16.In an experiment to determine the energy content of a peanut, a student burns the peanut and heats 20 cm³ of water. The temperature of the water rises from 20°C to 35°C. Given that the specific heat capacity of water is 4.2 J/g°C and 1 cm³ of water has a mass of 1 g, what is the energy released by the peanut?
Hard
- A1260 J
- B126 J
- C2940 J
- D840 J
17.A food label shows that a chocolate bar contains 250 kcal per serving. How many kilojoules does this represent? (1 cal = 4.2 J)
Medium
- A1050 kJ
- B250 kJ
- C105 kJ
- D2500 kJ
18.Which of the following is a risk of obesity mentioned in the source?
Easy
- AHeart disease
- BAnaemia
- CRickets
- DScurvy
19.A student conducts an experiment to compare the energy content of two different nuts. They burn each nut separately under a beaker of water and measure the temperature change. Which variable should be kept constant to ensure a fair test?
Hard
- AThe volume of water
- BThe type of nut
- CThe mass of the nut
- DThe time taken to burn
20.A food label shows the energy content per 100 g as 2000 kJ. If a person eats 50 g of this food, how much energy do they consume?
Hard
- A1000 kJ
- B2000 kJ
- C500 kJ
- D4000 kJ
21.The average man requires 10 500 kJ per day and the average woman requires 8 400 kJ per day. What is the ratio of the man's requirement to the woman's requirement?
Medium
- A5:4
- B4:5
- C5:3
- D3:5
22.A student investigates the energy content of a biscuit using a calorimeter. They obtain a temperature rise of 12°C for 25 g of water. The biscuit mass was 2 g. Calculate the energy content per gram of biscuit (specific heat capacity of water = 4.2 J/g°C).
Hard
- A630 J/g
- B315 J/g
- C1260 J/g
- D252 J/g
23.Which of the following is a reason why food labels should show the amount of each food group?
Medium
- ATo help people maintain a balanced diet
- BTo increase the price of food
- CTo make food look more appealing
- DTo reduce the energy content
24.What is the unit of energy used when referring to food?
Easy
- AKilojoule (kJ)
- BJoule (J)
- CCalorie (cal)
- DKilocalorie (kcal)
25.If a person eats too little food for a long period of time, what condition may eventually lead to death?
Medium
- AStarvation
- BObesity
- CMalnourishment
- DDiabetes
26.Basal metabolic rate is a measure of the energy content of food needed to survive when:
Easy
- Adoing no physical exercise
- Bdoing moderate exercise
- Cdoing heavy exercise
- Dbeing pregnant
27.Which of the following factors does NOT affect overall metabolic rate according to the source?
Medium
- AAge
- BGender
- CHeight
- DExercise levels
28.If a food label shows an energy content of 500 kcal per serving, how many kilojoules does that represent? (1 cal = 4.2 J)
Hard
- A2100 kJ
- B210 kJ
- C500 kJ
- D5000 kJ
29.Which of the following is NOT a factor affecting overall metabolic rate?
Medium
- APregnancy
- BBody mass
- CDiet type
- DAge
30.What is the term for not eating the right amount of food or having an unbalanced diet?
Easy
- AMalnourished
- BStarvation
- CObesity
- DOverweight
31.A student burns a sample of food under a test tube containing 20 cm³ of water. The temperature of the water rises from 20°C to 30°C. The energy released by the food is calculated using the formula: energy (J) = mass of water (g) × specific heat capacity (4.2 J/g°C) × temperature rise (°C). How much energy was released?
Medium
- A840 J
- B420 J
- C1680 J
- D210 J
32.A student uses a calorimeter to find the energy content of a peanut. The peanut (mass 0.5 g) is burned, heating 50 cm³ of water from 20°C to 45°C. The specific heat capacity of water is 4.2 J/g°C. What is the energy content of the peanut in kJ/g?
Hard
- A10.5 kJ/g
- B21 kJ/g
- C5.25 kJ/g
- D42 kJ/g
33.A food label shows that a serving contains 350 kcal. How many kilojoules does this represent? (1 cal = 4.2 J)
Medium
- A1470 kJ
- B350 kJ
- C83.3 kJ
- D147 kJ
34.A person consumes a meal containing 2500 kJ. If their basal metabolic rate (BMR) is 6000 kJ per day and they do no physical activity, how much more energy do they need to consume that day to meet their BMR?
Hard
- A3500 kJ
- B2500 kJ
- C8500 kJ
- D6000 kJ
35.A food label shows the energy content per 100 g as 1500 kJ. If a person eats 60 g of this food, how much energy do they consume?
Medium
- A900 kJ
- B1500 kJ
- C2500 kJ
- D600 kJ
36.The average man requires 10,500 kJ per day and the average woman requires 8,400 kJ per day. What is the ratio of the man's requirement to the woman's requirement in its simplest form?
Medium
- A5:4
- B10,500:8,400
- C4:5
- D1.25:1
37.A student investigates the energy content of a biscuit. They burn the biscuit under 25 cm³ of water and measure a temperature rise of 12°C. The specific heat capacity of water is 4.2 J/g°C. The biscuit mass was 2 g. What is the energy content per gram of biscuit?
Medium
- A630 J/g
- B315 J/g
- C1260 J/g
- D252 J/g
38.A food label shows per 100 g: energy 2000 kJ, protein 25 g, carbohydrate 60 g, fat 15 g. If a person eats 150 g of this food, how much energy and protein do they consume?
Hard
- A3000 kJ and 37.5 g protein
- B2000 kJ and 25 g protein
- C3000 kJ and 25 g protein
- D2000 kJ and 37.5 g protein
39.Which of the following is NOT a factor that affects overall metabolic rate according to the source?
Easy
- AHeight
- BAge
- CGender
- DExercise levels
40.A person consumes 2000 kJ more than their overall metabolic rate each day for a long period. What is a likely consequence?
Medium
- AWeight gain and possible obesity
- BWeight loss and possible starvation
- CNo change in weight
- DIncreased basal metabolic rate

Revision notes

## Food Energy Requirements - Food stores **chemical energy** transferred to us when eaten. - Energy unit: **joule (J)**, but for food we use **kilojoule (kJ)**. 1 calorie = 4.2 J. - **Malnutrition** from wrong amount or unbalanced diet. ### Eating Too Little - Weight loss → **starvation** (if prolonged) → **death**. ### Eating Too Much - Weight gain → **obesity** (excess body fat) → **heart disease** and **diabetes**. ### Metabolic Rate - **Basal metabolic rate (BMR)**: energy needed when inactive (just to survive). - **Physical activity level (PAL)**: extra energy needed for activity. - **Overall metabolic rate** = BMR + PAL. ### Factors Affecting Metabolic Rate - **Age**: children need less than adults; older adults need less. - **Gender**: men need more than women. - **Body mass**: larger mass → more food. - **Exercise**: more exercise → more food. - **Pregnancy**: requires more food. ### Daily Energy Needs - Average man: **10 500 kJ/day**. - Average woman: **8 400 kJ/day**. ### Food Labels - Important to show energy content and amounts of each food group to help maintain a balanced diet.

Joule (J): The unit of energy.
Kilojoule (kJ): Unit of energy used for food; 1 kJ = 1000 J.
Calorie: Another energy unit; 1 calorie = 4.2 J.
Malnourished: Having an unbalanced diet or not eating the right amount of food.
Starvation: Condition from eating too little food for a long time; can lead to death.
Obesity: Having too much body fat; can lead to heart disease and diabetes.
Basal metabolic rate: Measure of energy needed to survive when inactive.
Physical activity level: Measure of energy needed due to activity.
Overall metabolic rate: Combination of basal metabolic rate and physical activity level.

Flashcards

What unit is used for food energy?

The kilojoule (kJ) is used for food energy. One calorie equals 4.2 J.

What is the relationship between calorie and joule?

One calorie is equal to 4.2 joules.

What does malnourished mean?

Malnourished means not eating the right amount of food or having an unbalanced diet.

What happens if someone eats too little food for a long time?

They lose weight, which can lead to starvation and eventually death.

What happens if someone eats too much food for a long time?

They gain weight, which can lead to obesity, heart disease, and diabetes.

Define basal metabolic rate (BMR).

BMR is the energy needed to survive when inactive (no physical exercise).

What is physical activity level?

It is the energy needed due to physical activity.

How are BMR and physical activity level combined?

They combine to form overall metabolic rate.

List five factors affecting overall metabolic rate.

Age, gender, body mass, exercise levels, and pregnancy.

How does age affect metabolic rate?

Young children need less food than adults; older adults need less food than younger adults.

How does gender affect metabolic rate?

Men require more food than women.

How does body mass affect metabolic rate?

Larger body mass requires more food.

How does exercise affect metabolic rate?

More exercise requires more food.

How does pregnancy affect metabolic rate?

Pregnant women require more food.

What is the average daily energy requirement for a man?

10,500 kJ per day.

What is the average daily energy requirement for a woman?

8,400 kJ per day.

Why is food labelling important?

It shows energy content and amounts of each food group, helping us maintain a balanced diet.

What are two risks of obesity?

Heart disease and diabetes.

What is the unit of energy in science?

The joule (J).

What does 'starvation' lead to if it persists?

It can eventually lead to death.

Define obesity.

Obesity is when someone has too much body fat.

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