Endothermic exothermic worksheet|KS3 Chemistry|Teachit - Free Printable

Problem Analysis:

The task involves understanding the concepts of endothermic and exothermic reactions and applying this knowledge to complete sentences and classify reactions. Let's break it down step by step.

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Part 1: Complete Sentences

We are given a set of words in a box, and we need to fill in the blanks in the sentences using these words. The words are:
- energy
- heat
- chemicals
- transferred
- reactions
- decrease
- surroundings
- temperature
- increase

#### Sentence 1:
Exothermic reactions transfer …………………… from the reacting …………………… into the surroundings.

- Exothermic reactions release energy as heat.
- The reacting substances (chemicals) transfer heat to the surroundings.

Completed sentence:
Exothermic reactions transfer heat from the reacting chemicals into the surroundings.

#### Sentence 2:
We can measure the energy transferred by measuring the …………………… increase in the reaction.

- Energy transfer in exothermic reactions is often measured by the temperature increase of the surroundings or the reaction mixture.

Completed sentence:
We can measure the energy transferred by measuring the temperature increase in the reaction.

#### Sentence 3:
During endothermic …………………… there is a …………………… in temperature.

- Endothermic reactions absorb energy, causing a decrease in temperature.

Completed sentence:
During endothermic reactions, there is a decrease in temperature.

#### Sentence 4:
This is because energy is …………………… from the …………………… into the reacting chemicals.

- In endothermic reactions, energy is absorbed from the surroundings into the reacting chemicals.

Completed sentence:
This is because energy is transferred from the surroundings into the reacting chemicals.

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Part 2: Label Reactions as Endothermic or Exothermic

We are given five reactions and need to classify them as either endothermic or exothermic.

#### Reaction 1: Respiration
- Respiration is the process by which organisms break down glucose to produce energy. This process releases heat and is a common example of an exothermic reaction.
- Classification: Exothermic

#### Reaction 2: Neutralisation
- Neutralisation is a chemical reaction between an acid and a base, producing salt and water. This reaction typically releases heat.
- Classification: Exothermic

#### Reaction 3: Photosynthesis
- Photosynthesis is the process by which plants convert sunlight, carbon dioxide, and water into glucose and oxygen. This process requires energy from sunlight and absorbs heat, making it endothermic.
- Classification: Endothermic

#### Reaction 4: Thermal Decomposition
- Thermal decomposition involves breaking down a compound into simpler substances using heat. This process absorbs heat from the surroundings.
- Classification: Endothermic

#### Reaction 5: Burning Fuels
- Burning fuels (e.g., combustion) releases a large amount of heat and light. This is a classic example of an exothermic reaction.
- Classification: Exothermic

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Final Answer

#### Part 1: Completed Sentences
1. Exothermic reactions transfer heat from the reacting chemicals into the surroundings.
2. We can measure the energy transferred by measuring the temperature increase in the reaction.
3. During endothermic reactions, there is a decrease in temperature.
4. This is because energy is transferred from the surroundings into the reacting chemicals.

#### Part 2: Classification of Reactions
1. Respiration: Exothermic
2. Neutralisation: Exothermic
3. Photosynthesis: Endothermic
4. Thermal Decomposition: Endothermic
5. Burning Fuels: Exothermic

Boxed Final Answer:
\[
\boxed{
\begin{array}{l}
\text{1. Exothermic reactions transfer heat from the reacting chemicals into the surroundings.} \\
\text{2. We can measure the energy transferred by measuring the temperature increase in the reaction.} \\
\text{3. During endothermic reactions, there is a decrease in temperature.} \\
\text{4. This is because energy is transferred from the surroundings into the reacting chemicals.} \\
\text{5. Respiration: Exothermic} \\
\text{6. Neutralisation: Exothermic} \\
\text{7. Photosynthesis: Endothermic} \\
\text{8. Thermal Decomposition: Endothermic} \\
\text{9. Burning Fuels: Exothermic}
\end{array}
}
\]